Musculoskeletal Disorders in the Workplace Principles and Practice 2nd Edition - nordin

158 Chapter 5b ● Biomechanics of the shoulder and elbow complex The rotator cuff is a series of coalesced tendons from four Glenohumeral kinematics describes the motion of the humeral muscles. Moving over the head of the humerus from anterior head in the glenoid cavity without consideration of forces to posterior, these muscles include the subscapularis, supraspina- contributed by surrounding musculature. This description can tus, infraspinatus, and teres minor, which work in concert to be for either two-dimensional planar motion or three-dimensional stabilize and afford discrete motion of the shoulder. These mus- spatial motion.49 Planar motion of the glenohumeral joint can be cles originate from the scapula and form a condensed tendinous divided into three modes of articulation: sliding, spinning, and sleeve around the anterior, superior, and posterior aspects of rolling41 (Fig. 5b.3). In sliding, the contact point is constant on the humeral head. The most anterior muscle, the subscapularis, the translating humeral head but is always changing on the fans out from the anterior scapula over to the lesser tuberosity stationary glenoid cavity. The center of rotation is the center of of the humerus. When contracted, it acts as an internal rotator curvature of the glenoid. During spinning, the contact point is of the humerus. always changing on the rotating humeral head but is constant on the stationary glenoid cavity. The center of rotation for spinning At the most superior portion of the cuff is the supraspinatus, is the center of curvature of the humeral head. In rolling, the the rotator cuff muscle most often implicated in shoulder point of contact is always changing on both the humeral head pathology. In its course to its insertion, it travels beneath the and the glenoid cavity, with the center of rotation being the coracoacromial arch, forming the floor of the subacromial space. contact point itself. Any two of these three divisions can be com- In this space between the acromion and the supraspinatus ten- bined to describe the planar motion of the glenohumeral joint.41 don is the soft subacromial bursa. The relationship between the supraspinatus and the acromion is important to appreciate, Spatial motion can best be explained in terms of degrees of especially when considering conditions like impingement syn- freedom. In general, an unconstrained rigid body has six degrees drome, where the subacromial space may be appreciably decreased of freedom—three translations and three rotations about the in size, leading to pathology. When contracted, this muscle is a orthogonal x-, y-, and z-axes (Fig. 5b.4). In its normal range of shoulder abductor in the plane of the scapula.6 Moving posteri- motion, the glenohumeral joint is capable of three rotations orly on the cuff, the infraspinatus muscle functions to depress about three orthogonal coordinate axes and thus has three the humeral head and externally rotate the humerus. The final degrees of freedom. In terms of joint motion, these three rota- and most posterior rotator cuff muscle, the teres minor, is an tions are defined as flexion/extension, abduction/adduction, and external rotator of the humerus. internal/external rotation. These motions are constrained by soft tissues, ligaments, articulations, and muscles. In flexion/exten- Although thought of primarily as an elbow muscle, the biceps sion, the humerus can generally be moved in the sagittal plane has a role in shoulder stability and pathology also. The biceps through a range of about 170 degrees.41 Abduction/adduction can is unique in that it is one of the body’s few muscles that origi- be achieved over a range of 180 degrees41 in the coronal plane. nate within a joint. Because of this intraarticular labral origin, The range of motion for internal/external rotation totals approx- the LHB is implicated in a great deal of labral pathology. imately 150 degrees.41 Many overhead motions are achieved Although functioning primarily as an elbow flexor and supinator through combinations of flexion/extension and abduction/ of the forearm, the biceps is believed to play a role in the shoul- adduction, with additional aid from the scapulothoracic artic- der as a humeral head depressor and as a significant stabilizer ulation at motion extremes. This type of overhead motion has to inferior subluxation.33,60 been reported as a source of numerous shoulder injuries, includ- ing those suffered during occupational tasks.22 A number of other parascapular muscles act around the shoul- der joint but do not necessarily contribute directly to gleno- Constraint humeral range of motion or stability. The three largest of these are the trapezius, serratus anterior, and latissimus dorsi muscles. The bony architecture of the shoulder affords this joint an excep- The bulky trapezius muscle mainly functions as a scapular tional range of motion. It is achieved, however, only with an retractor. By doing so, it rotates the inferior angle of the scapula obligatory reduction in its biomechanical stability. In compen- laterally, shrugs the shoulders, and clamps the scapula to the sation, both static and dynamic stabilizers help orchestrate a chest wall. Sometimes known as the “boxer’s muscle,” the serra- balance between mobility and stability. tus anterior primarily protracts and medially rotates the scapula, drawing it closer to the posterior chest wall. The serratus anterior When viewing plain radiographs, the glenohumeral joint is active in all motions of the humerus but more so in flexion. appears to function like a sphere articulating on a flat glenoid The latissimus dorsi is an enormous back muscle that internally surface. Historically, it was therefore assumed that the osseous rotates and adducts the humerus and extends the shoulder. geometry of the joint surfaces provided little if any inherent stability to the shoulder. Cadaveric studies, however, have deter- Biomechanics of the glenohumeral joint mined that the articular geometry of the shoulder does play a substantial role in stabilization. Using gross measurements and Kinematics magnetic resonance imaging, investigators have documented that the radius of curvature of the average glenoid is about 2 mm This concise discussion of biomechanics focuses on the primary greater than that of the corresponding humeral head.28 source of motion at the shoulder, the glenohumeral joint. It should be noted however, that the AC, SC, and scapulotho- Using stereophotogrammetry, another center reported similar racic articulations do also have roles, albeit less so, in the overall findings and determined that the mating humeral head and mechanics of the upper extremity. glenoid articular surfaces were in fact congruent.58 When the articular cartilage surfaces were analyzed, furthermore, it was

Chapter 5b ● The shoulder 159 Figure 5b.3 Planar glenohumeral articulation. Included are spinning, rolling, and sliding motions. These motions may occur either in isolation or in combination. (From Zuckerman JD, Matsen FA: Biomechanics of the shoulder. In M Nordin, VH Frankel, eds: Biomechanics of the musculoskeletal system. Philadelphia, 1989, Lea & Febiger.) z observed that the actual articulating surfaces conformed more than previously thought.58 Enlarging the articulating area is 3 2 thought to add to stability by decreasing the potential for 6 y humeral head translation and by increasing what Fukuda and colleagues17 referred to as the “constraining wall height” of the 5 joint. Using this technique57 and Fugi Prescale film,69 contact 4 areas within the glenohumeral joint have been documented also, 1 ranging from approximately 0.75 cm2 with the arm at the side and 5 cm2 at 90 degrees of abduction. Additionally, contact x pressure within the joint was found to decrease with increasing abduction to 90 degrees.69 Figure 5b.4 Orthogonal coordinate axes, illustrating six degrees of freedom—three translations (1-3) and three rotations (4-6). The remaining static stabilizers of the shoulder joint include the glenoid labrum, the joint capsule, and the glenohumeral and coracohumeral ligaments. These coordinate to resist joint translation primarily by preventing displacement through their presence and secondarily by imparting increased joint contact forces resisting the displacement.24 The first of these structures, the glenoid labrum, is a meniscus-like thickening of fibrous tissue that is triangular in cross-section and surrounds the rim

160 Chapter 5b ● Biomechanics of the shoulder and elbow complex Shoulder Anatomy and Biomechanics Figure 5b.5 The glenoid labrum. The labrum’s role can be thought of as extending the surface area of the socket, much as adding to the bank of a road deepens a curve. (From Flatow E: Shoulder anatomy and biomechanics. In M Post, L Bigliani, E Flatow, R Pollock, eds: The shoulder: operative technique. Philadelphia, 1998, Lippincott, Williams & Wilkins.) AB of the glenoid cavity (Fig. 5b.5). Previously thought to be com- middle glenohumeral ligament has been demonstrated to be a sig- posed of fibrocartilage, the labrum is mostly dense fibrous tissue nificant constraint to anterior displacement of the humerus.14,43 with few elastic fibers.43 Often conceptualized as a bumper that Along with the anterior capsule, the middle glenohumeral ligament prevents the humeral head from excursion out of the glenoid, becomes taut when the arm is abducted and externally rotated. its role in enhancing the stability of the glenohumeral joint has been questioned, as some investigators have found that it The IGHL is the ligament thought to be responsible for offers little in overall shoulder stability.43,63 As a whole, however, most of the shoulder’s static stability. Its geometry has classically the labrum does play some role in shoulder constraint, but its been described as having three distinct components—a superior contribution is likely complementary.41 Supraspinatus The joint capsule of the shoulder is a relatively thin sheet of fibrous tissue. Depending on the position of the shoulder, the Long head capsule imparts a variable contribution to glenohumeral joint of triceps stability. In general, anterior shoulder structures are taut when the arm is externally rotated. Superior, inferior, and posterior Anterior View structures are accordingly tightened when the arm is adducted, abducted, and internally rotated, respectively. The most obvious Intraspinatus Posterior View and important portions of the shoulder capsule that confer stability are sometimes referred to as the capsule-ligament com- Teres minor SGHL plex. This complex consists of superior, middle, and inferior por- MGHL tions that along with the CHL define the ligamentous structures Posterior axillary providing constraint to the shoulder joint41 (Fig. 5b.6). In gen- pouch of IGHL Subscapularis eral, the capsular structures participate in mechanically stabi- Superior band lizing the joint at the extremes of motion, though they may also Long head of IGHL have roles in proprioception. of triceps Anterior axillary Because it extends from the coracoid process to the lesser pouch of IGHL tuberosity, the CHL is thought to participate in suspending the humerus in the glenoid when the arm is at the side. Its role in Capsule stability, however, remains controversial.60 The superior gleno- humeral ligament is a fibrous structure that becomes tight when Figure 5b.6 The glenohumeral ligaments. The glenohumeral the arm is adducted at the side. As it tightens, it acts primarily ligaments are thickenings in the capsule of the shoulder and function as an inferior stabilizer and likely functions along with the as passive check reins, particularly at the extremes of motion. CHL and the rotator cuff to prevent inferior translation of the humeral head on the glenoid.48,68 Often well developed, the

Chapter 5b ● The shoulder 161 band and anterior and posterior axillary pouches.65 The geome- in day-to-day activities and in strenuous work tasks such as heavy try and mechanical properties of these distinct areas of the IGHL lifting, abduction, and overhead use. The loading that occurs in suit it well for its role as the primary static anterior stabilizer the glenohumeral joint during normal motion has been reported of the glenohumeral joint.8 Slack and redundant with the arm to be as high as 0.89 times body weight at 90 degrees of abduc- adducted, the IGHL is the primary static restraint to anteroinfe- tion, and it is increased appreciably when weight is held.50 rior subluxation, particularly in abduction and external rotation, a position associated with increased anterior instability.9 In this Most of the strength and gross motion at the joint is facili- position the more anterior structures become taut, whereas in tated by the massive deltoid muscle, the three primary sections internal rotation the posterior aspect of the IGHL is tense. of which function differently depending on the direction of a force and the arm position when a load is applied. In general, The dynamic stabilizers of the shoulder joint include the the more anterior portion is important in forward elevation, rotator cuff, biceps, and deltoid muscles. Directly they act as a whereas the posterior portion plays a significant role in posteri- bulky barrier with inherent passive muscle tension that resists orly directed motion such as extension. The middle fibers of the translation of the humeral head, and they play an important role deltoid make relative contributions to both of these movements in stability by providing compressive forces on the humerus but are involved mostly in shoulder abduction strength, to into the glenoid socket. Indirectly, the dynamic stabilizers exert which the deltoid contributes over 60%.13 their effect by moving the joint into positions that tighten the capsular-ligamentous complex,41 thus engaging these stabilizing Although debated, the relative contribution of the supraspina- structures. tus to overall abduction of the shoulder has more recently been shown to be responsible for between 19% and 33% of the total As described in the section on anatomy, the rotator cuff is abduction force generated at the shoulder.30 Its length-tension a series of four muscles that coalesce to form a tendinous arc of curve demonstrates maximum force at about 30 degrees of eleva- tissue around the glenohumeral joint. In addition to affording tion.5 In selective nerve block studies, the infraspinatus and the shoulder with discrete motions, these muscles also provide teres minor muscles have been found responsible for as much as stability. Anteriorly, the subscapularis muscle forms a musculo- 60% and 45% of the external rotation force that can be gener- tendinous curtain from the scapula to the lesser tuberosity. ated at the shoulder, respectively.13 The subscapularis muscle is In doing so, it is thought to be the most important dynamic the only primary internal rotator of the shoulder and as such anterior stabilizer.15 This stability is greatest in external rotation is responsible for most of the force in that movement. and from 0 to 45 degrees of abduction.36,65 At 90 degrees of abduction, the IGHL seems to play the most important role.65 Mechanical properties of articular cartilage Of all the rotator cuff muscles, the subscapularis provides the most resistance to posterior subluxation when the arm is in for- and ligaments ward flexion.10 Superiorly, the supraspinatus muscle has been reported to be an important restraint to inferior translation of When considering shoulder biomechanics, it is important to the humerus. This action has been observed in cadaveric speci- understand the mechanical behavior of the soft tissues (namely mens where the supraspinatus was found to be an inferior stabi- ligaments and cartilage) associated with the glenohumeral joint, lizer more effective than any other cuff muscle.60 Investigators the subject of various experimental techniques (Table 5b.2). demonstrated that moving posteriorly on the cuff, the infra- Tests of the mechanical properties of glenohumeral articular spinatus, the teres minor, and occasionally the supraspinatus cartilage have included both indentation44 and tensile testing.70 function together with the subscapularis to impart notable On average, the aggregate modulus for glenohumeral joint artic- posterior stabilization.10,46 ular cartilage ranges from roughly 0.5 to 0.9 MPa.44 Compressive and shear properties of articular cartilage are important because A complete analysis of the relative contributions of the rotator of the nature of their role in dynamic articulating surfaces. cuff muscles to glenohumeral joint stability is beyond the scope of this text. It is notable, however, that these muscles do not Partly because ligaments are anisotropic, in that they have simply exist and function in isolation. Rather, they have been different properties in the longitudinal and transverse directions, demonstrated to function in concert, with both anterior and and partly because their primary function is joint stabilization posterior force coupling that yields enhanced joint stability.54 typically through tensile loading, the most common method of The contribution of the biceps muscle to overall glenohumeral Table 5b.2 Mechanical properties of some key stability is also important. As the LHB tendon courses over the glenohumeral ligaments curved head of the humerus, it acts like a cable wrapping around a pulley. When the biceps is activated, it compresses the humeral Failure Stiffness Ultimate Elastic head into the glenoid.4 Additionally, the biceps has been sug- Ligament load (N) (N/mm) stress modulus gested to be as important as the rotator cuff to glenohumeral (MPa) (MPa) stability.29 Because of its size (20% of overall shoulder muscle mass), the deltoid’s contribution to shoulder stability is thought Superior 101.911 17.411 —— to be noteworthy but remains undefined.7 glenohumeral — — 359.811 36.711 5.2, 5.5, 5.6* 38.7, 30.3, Kinetics Inferior 41.9* glenohumeral In contrast to kinematics, glenohumeral kinetics is the study of —— joint motion with respect to the forces responsible for it. The Coracohumeral muscles and ligaments of the rotator cuff carry appreciable loads *Values are for superior, anterior, and posterior regions, respectively.8

162 Chapter 5b ● Biomechanics of the shoulder and elbow complex Toe region Linear region Yield/failure addressed by testing them. Recently, animal models have gath- ered significant interest and use to address questions about Stress the biomechanics of the shoulder and its injuries. The most fundamental issue that must be addressed when selecting any Strain animal model is its biofidelity with respect to the body region of interest. Figure 5b.7 Typical tensile test of a ligament, showing the toe, linear, For the shoulder, several animal models have been used in and yield/failure regions. studying tendon and rotator cuff injury and repair. New Zealand white rabbits, for example, have been used to study muscle heal- obtaining mechanical properties is the quasistatic tensile test. ing characteristics after supraspinatus tendon reattachment.39,66 However, more sophisticated methods have enabled precise Other works have investigated rotator cuff repair both in vitro two-dimensional analysis of the glenohumeral joint. In situ and in vivo using infraspinatus tendons of sheep.18,19 strain fields in the anteroinferior shoulder capsule have been quantified in this way using stereoradiogrammetry, showing that Soslowsky et al59 set out to identify an effective animal model strains are generally higher on the glenoid side of the capsule for studying rotator cuff injuries by examining anatomic charac- than on the humeral side.35,37 teristics of the shoulder in several different species. In an analy- sis involving 34 criteria applied to 37 animals, the rat emerged as All biologic soft tissues demonstrate both nonlinear and the only model to satisfy all criteria while still being practical for viscoelastic mechanical behavior under loading. The nonlinear- experimental research. The most distinguishing characteristic ity is characterized initially by a relatively large increase in that makes the anatomy of the rat shoulder comparable with that elongation with respect to load (Fig. 5b.7). In tensile testing, of a human is the position of the acromion and its associated this “toe” region represents the straightening and aligning of enclosed arch in relation to the supraspinatus tendon.59 Sprague- collagen fibers in the longitudinal axis, that is, the direction of Dawley rats have since been used effectively in numerous inves- loading. This is followed by a linear region, over which the tigations into the roles of overuse and extrinsic factors in rotator mechanical properties such as stiffness are typically evaluated. cuff injuries. In the laboratory setting, overuse activity has The ensuing region of nonlinear yield culminates with the failure produced a reproducible injury in the rat shoulder comparable of the specimen. with that seen clinically in the rotator cuff.61 Injuries stemming from overuse in combination with extrinsic compression have In addition to behaving nonlinearly, soft tissues are also resulted in relatively high maximum stresses and elastic moduli considered viscoelastic due to the rate dependence of their when compared with each of the two factors alone, indicating mechanical properties. When loaded rapidly, a ligament tends to that rotator cuff tendinosis is not typically attributable to a be stiffer than when loaded at a lower rate. IGHL regions have single factor.62 been shown to have up to 62% increased modulus when loaded an order of magnitude more rapidly.44 A phenomenon associ- Prevention of disability through ergonomics ated with soft tissue viscoelasticity is the hysteresis effect. When a ligament is cyclically loaded and returned to its resting state, the Three of the most prominent risk factors to emerge from studies load-deformation response shifts until equilibrium is eventually of workplace ergonomics are static or extreme posture,25,51 cycli- reached after 10-20 cycles.38 For this reason, biomechanical testing cal occupational motions,16,21 and external loading.16,47 The risk should begin with a period of preconditioning in which the of shoulder disorder has been reported to be two to three times specimen is cyclically loaded within its normal physiologic range. higher in occupations requiring abduction or flexion beyond 90 degrees for at least 10% of the time performing the task.51 Although biomechanical studies demonstrated that soft This combination of awkward shoulder posture and long time tissue properties change as a function of age38 and epidemiology periods has been identified as a key risk factor for disorders.56 indicates that shoulder and upper limb disorders tend to arise The occurrence of shoulder tendinitis has been found to be two over time,34 age has not shown a consistently strong association to three times higher in workers with highly repetitive or cyclical with shoulder tendonitis in the workplace environment. This work tasks involving the upper limbs.16 External hand loads is due partly to older workers often leaving their jobs because in combination with humeral abduction have been linked to of the injury, resulting in “survivor bias.”23 increased rotator cuff muscle pressure, which can have detrimen- tal effects on the shoulder.47 Conversely, when an occupation Animal models does not require appreciable loading, the risk of shoulder ten- dinitis is lower.16 With sufficient effort focused on these issues in Although cadavers have proven beneficial in experimental the workplace through improved ergonomic conditions, resulting biomechanics research, certain important questions cannot be shoulder disorders may be appreciably reduced. THE ELBOW Anatomic considerations Complex in its articular geometry, the elbow is an important link in the lever arm chain of the upper extremity that facilitates a

Chapter 5b ● The elbow 163 { Medial Humerus Tuberosity Humerus Medial Medial epicondyle Condyle supracondylar crest Lateral Capitulum Coronoid Trochlea Lateral fossa Head supracondylar crest Neck Medial epicondyle Radial fossa Radius Lateral epicondyle Trochlea Capitulum Coronoid Ulna Tuberosity Olecranun Head process Coronoid process Neck Radial notch of ulna B Trochlear notch Tuberosity Tuberosity Radius Ulna A Ulnar collateral ligament Annular ligament C Figure 5b.8 Bones of the elbow, anterior (A) and medial (B) views. The orientation of the three components of the medial collateral ligament include the anterior, posterior, and transverse bundles. broad range of motion, the absence of which causes significant depressions on the distal humerus that participate in the ulno- functional impairment. A working knowledge of the elbow’s humeral joint as well: the coronoid and olecranon fossae. As anatomy is thus important in any effort to understand the the joint goes through flexion and extension, the olecranon and biomechanics at this articulation. The elbow is a trochleo- coronoid fossae accommodate their similarly named processes ginglymoid joint composed of three bones; the distal humerus on the proximal ulna. and the proximal ulna and radius (Fig. 5b.8). The three articula- tions at the elbow are the ulnohumeral, radiohumeral, and The proximal ulna is composed of two arced processes—the radioulnar joints. olecranon and coronoid—separated from each other anteriorly by the greater and lesser sigmoid notches. A lateral indentation Articulations in the lesser sigmoid notch, the radial notch, provides articula- Ulnohumeral Joint As the metaphyseal bone of the distal tion with the proximal radius. Viewed laterally, the proximal ulna resembles a claw that tightly grasps the trochlea of the humerus flares out distally, it forms two supracondylar regions distal humerus. The olecranon is a large posterior bony process that end in medial and lateral epicondyles. These epicondyles that provides the posterior articulation for the ulnohumeral joint, flank two odd-shaped asymmetric condyles. The condyles prevents posterior displacement of the humerus, and serves as compose the distal articular surface of the humerus: the trochlea the site of attachment for the triceps tendon. Anteriorly, the medially and the capitellum laterally. The ulnohumeral joint is coronoid provides the anterior articular surface of the joint, essentially a hinge governed by the intimate matching geometry prevents anterior translation of the humerus, and serves as the of the trochlea and proximal ulna. The most constrained portion site for the distal insertion of the brachialis muscle. of the elbow joint, this articulation allows only flexion and extension. On the humeral side, the trochlea resembles a spool Although strong transverse and oblique fibers do exist, the of thread with broad ends (of which the medial is larger) that capsule of the elbow is generally weak and reinforced primarily converge into a narrow trochlear groove. In the frontal plane by strong ligaments medially and laterally that stabilize the joint the trochlea has approximately 6 degrees of valgus tilt that helps against varus and valgus forces (Fig. 5b.8b). On the medial side dictate the carrying angle of the normal elbow. There are two of the elbow, the medial collateral ligament (MCL) (often referred to as the ulnar collateral ligament) has a transverse

164 Chapter 5b ● Biomechanics of the shoulder and elbow complex ligament and an anterior and posterior bundle. Laterally, the tendon on the olecranon process of the ulna. Adjacent to the radial collateral ligament complex is composed of the annular triceps insertion is a small triangularly shaped muscle called ligament, radial collateral ligament proper, and lateral ulnar the anconeus that is minimally involved in forearm extension. The collateral ligament (LUCL). The annular ligament is a strong ring epicondyles of the distal humerus provide the origin for a num- of tissue that loops around the radial head to hold it against ber of forearm muscles that act mostly on the wrist. Table 5b.3 the proximal ulna at the proximal radioulnar joint. The radial describes the muscles of the arm. collateral ligament extends from the lateral epicondyle to the annular ligament and is taut throughout most of the normal Biomechanics of the elbow range of motion at the elbow. Invariably present, the LUCL extends from the lateral epicondyle to the supinator crest on the Kinematics proximal ulna. In terms of spatial motion, the elbow is considered to have two Radiohumeral Joint The medial condyle of the distal humerus, degrees of freedom, flexion/extension and supination/pronation. the capitellum (l. little head), is spherical and covered by articular Flexion/extension is essentially a hinge-like motion that occurs cartilage. At the radiocapitellar joint it articulates with the cylin- at the ulnohumeral joint. This motion defines the carrying angle, drical head of the radius. The radiocapitellar joint allows flexion- that formed by the ulna and the humerus. The rotational axis extension and pronation-supination and also undergoes varus for flexion/extension is formed by the trochlea and capitellum. and valgus moments. As the forearm rotates into either pronation The normal range of motion in flexion, from 0 to 150 degrees, is or supination, the radial head spins underneath the capitellum. restricted by bony impingement of the radial head and fossa, impact between the coronoid process and fossa, and muscular Radioulnar Joint The radial head is bound to the ulna by the tension from the triceps.2 Extension is limited by the impinge- annular ligament and, due to its location, acts as a primary ment of the olecranon process on the olecranon fossa and ten- restraint to valgus force. The proximal radioulnar joint allows sion of the anterior and medial ligaments and flexor muscles.31 pronation and supination. Like the radiohumeral and ulnohumeral For supination/pronation, the axis of rotation passes through joints, this joint is enveloped in the elbow capsule. the distal ulna and the center of the radial head.2 The elbow is normally capable of approximately 75 degrees of pronation and Muscles 85 degrees of supination, or 160 degrees of total motion, limited primarily by muscles and secondarily by ligaments.2 The muscles acting on the elbow play defined roles in facilitating its motion. In general, muscles crossing the elbow on the ante- Constraint rior surface of the cubital fossa are elbow flexors, whereas those located posteriorly function to extend the elbow. As described In addition to the aforementioned stability afforded by the in the shoulder section above, the biceps muscle crosses both unique topography of the distal humerus and proximal ulna, the shoulder and the elbow joints. Its function at the elbow is to additional constraint is provided by the elbow capsule and the flex the extended elbow and supinate the flexed forearm, as in periarticular ligaments.3,45 At the elbow, the medial and lateral tightening a screw with the right hand. Like the biceps, the ligamentous complexes provide most of the additional stability brachioradialis and brachialis muscles flex the elbow. Posteriorly to the bony configuration. On the medial side of the elbow is on the elbow is the triceps brachii muscle, its primary extensor. the MCL. Cadaveric studies have determined that the anterior Composed of a medial lateral and long head, the muscle extends band of the MCL is the most important section of the ligament the entire length of the posterior brachium to insert as a thick because it is the primary stabilizer against a valgus force.42 Table 5b.3 Muscles of the arm Muscle Origin Insertion Innervation Action Forearm flexion, supination of Biceps brachii Short head: coracoid process of scapula Tuberosity of the radius and Musculocutaneous n. Brachialis Long head: supraglenoid tubercle of scapula flexed forearm Distal one half of anterior humerus forearm via bicipital aponeurosis (C5-C6) Forearm flexion Flexes and adducts humerus Coronoid process and tuberosity Musculocutaneous n. Extends forearm of ulna (C5-C6) Assists triceps in forearm extension Coracobrachialis Tip of coracoid process Middle third of medial surface Musculocutaneous n. of humerus (C5-C7) Triceps brachii Long head: infraglenoid tubercle Proximal olecranon process Radial n. (C6-C8) Anconeus Lateral head: posterior surface of humerus Lateral surface of olecranon Radial n. (C7-C8, T1) superior to spiral groove Medial head: posterior surface of humerus inferior to spiral groove Lateral epicondyle of humerus n., nerve.

Chapter 5b ● References 165 Clinically, this becomes particularly relevant when the radial tissue engineering approaches are making significant strides toward head (a secondary valgus stabilizer) is no longer functioning improving the healing response of injured tissues such as the (e.g., due to fracture). rotator cuff or in creating replacement structures such as for ligaments and joints. Investigators have begun using resorbable The lateral collateral ligamentous complex functions mostly tissue scaffolds in the hope of regenerating new tendon. Using as a varus stabilizer of the elbow. The major component of materials like porcine small intestine submucosa, human dermis, the radial collateral ligament complex contributing stability to and woven starch fabrics, some centers have documented varus and rotatory stability of the elbow is the LUCL.2 Overall, encouraging results in engineering new tissue growth. Advances the LUCL specifically is responsible for most of the lateral sta- in these areas will likely yield significant benefit to the patient bilization.2 In addition to holding the radius in the proximal population in the near future. radioulnar joint, the annular ligament also provides some stability against varus and valgus stress.55 The use of in vivo techniques and measurements in lieu of cadaveric investigations is another developing trend. In vivo meas- Kinetics urements of loading and motion in both normal and abnormal states will further our understanding of the mechanics of the shoul- Contact in the elbow is typically described with respect to the der and elbow joints. Noninvasive techniques have begun to play ulnohumeral joint. The three most common methods of contact a more important role in enhancing our understanding of upper measurement in the elbow are silicone casting, cartilage staining, extremity biomechanics. Together with three-dimensional recon- and Fugi Prescale film. Having evaluated all three techniques, structed computer-aided tomograms, some investigators have used Stormont et al64 identified silicone casting as the optimal method in vivo fluoroscopic imaging of the shoulder and elbow to gain for studying elbow contact. In a study using a wax casting exciting new insight into their kinematics. Using these techniques, technique,20 contact was reported to be concentrated on the they have gained a more comprehensive appreciation for the load- medial part of the lower trochlear notch with the elbow in full ing, contact area, and dynamic motion at these articulations. This extension. At 90 degrees of flexion, the contact appeared pre- information has helped in the development of better total joint dominantly as a band extending from the lower medial to upper arthroplasties. Ongoing work is making use also of magnetic reso- lateral trochlear notch. At full flexion, the band of contact area nance imaging to measure tendon strain fields in the shoulder. increased, and contact between the radial head and capitulum became more pronounced.20 It was noted in a different study Another area that has seen recent development and is likely that with increased external load, contact area increased and its poised for significant advancement is in the use of computer location became increasingly lateral.64 Although experimentally models of the shoulder complex. Based on original work by difficult on curved articulations, the use of Fugi Prescale film both Högfors et al26,27 and van der Helm,67 efforts to combine provides measurements of contact pressure as well as area. finite element and three-dimensional modeling have yielded new methodologies for investigating the shoulder. Using a six-degree- Like the shoulder, the mechanical behavior of elbow liga- of-freedom electromagnetic tracking device, investigators have ments is nonlinear and viscoelastic, although there is substan- obtained complete kinematic descriptions of shoulder motion.40 tially less information available. Properties for the medial and Additionally, with these three-dimensional models, investigators radial collateral ligamentous complexes, however, have been have been able to estimate muscle attachment sites and reliably reported.52 The radial collateral ligament is reported to have apply them to geometric bone models.32 As the horizon for a mean ultimate stress of 15.9 MPa and elastic modulus of new advances in orthopedic bioengineering broadens, we hope 54.3 MPa. The MCL has been found to be stronger and less to continue to find even more efficacious applications toward elastic, with ultimate stresses of 20.7 and 19.2 MPa and elastic the prevention and treatment of injury and disability at the moduli of 117.8 and 96.8 MPa for the anterior and posterior shoulder and elbow. bundles, respectively. REFERENCES In the workplace, flexion/extension is typically involved in lifting tasks, whereas supination/pronation in combination 1. An KN, Chao EYS, Kaufman KR: Analysis of muscle and joint loads. In VC Mow, with force exertion has been cited as a risk factor for medial WC Hayes, eds: Basic orthopaedic biomechanics, ed 2. Philadelphia, 1997, and lateral epicondylitis in tasks involving repeated twisting Lippincott-Raven, pp. 1-35. motions.21 As with the shoulder, it has been shown that workers in high-repetition jobs are two to three times more likely to develop 2. An KN, Morrey BF: Biomechanics of the elbow. In BF Morrey, ed: The elbow and conditions such as elbow tendinitis than those performing its disorders, ed 3. Philadelphia, 2000, WB Saunders, pp. 43-60. low-repetition tasks.34 3. An KN, Morrey BF, Chao EYS: The effect of partial removal of proximal ulna on elbow NOVEL DEVELOPMENTS AND constraint. Clin Orthop Relat Res 209:270-279, 1986. FUTURE DIRECTIONS 4. Andrews JR, Carson WG Jr, McLeod WD: Glenoid labrum tears related to the long head An important area that is gaining momentum in orthopedic of the biceps. Am J Sports Med 13:337, 1985. biomechanics is in the field of tissue engineering, which strives to combine biologic and mechanical elements. Specifically, the 5. Atwater AE: Biomechanics of overarm throwing movements and of throwing injuries. concept of functional tissue engineering mandates consideration Exerc Sport Sci Rev 7:43-85, 1979. of mechanical properties and functional capabilities when dealing with tissues that are structurally vital.12 In particular, functional 6. Basmajian JV, Bazant FJ: Factors preventing downward dislocation of the adducted shoulder joint. An electromyographic and morphological study. Am J Orthop 41A: 1182-1186, 1959. 7. Bassett RW, Browne AO, Morrey BF, An KN: Glenohumeral muscle force and moment mechanics in a position of shoulder instability. J Biomech 23:405-415, 1990. 8. Bigliani L, Kelkar R, Flatow E, Pollock R, Mow V: Glenohumeral stability: biomechanical properties of passive and active stabilizers. Clin Orthop Relat Res 330:13-30, 1996.

166 Chapter 5b ● Biomechanics of the shoulder and elbow complex 9. Bigliani LU, et al: Tensile properties of the inferior glenohumeral ligament. J Orthop 41. Morrey BF, Itoi E, An KN: Biomechanics of the shoulder. In CA Rockwood, FA Matsen, Res 10:187-197, 1992. eds: The shoulder, ed 2. Philadelphia, 1998, Saunders, pp. 233-276. 10. Blasier RB, Soslowsky LJ, Malicky DM, Palmer ML: Posterior glenohumeral subluxation: 42. Morrey BF, Tanaka S, An KN: Valgus stability of the elbow. A definition of primary active and passive stabilization in a biomechanical model. J Bone Joint Surg and secondary constraints. Clin Orthop Relat Res 265:187-195, 1991. 79(3):433-440, 1997. 43. Moseley HE, Overgaard B: The anterior capsular mechanism in recurrent anterior 11. Boardman ND, Debski RE, Warner JJ, Taskiran E, Maddox L: Tensile properties of the dislocation of the shoulder. J Bone Joint Surg 44B:913, 1962. superior glenohumeral and coracohumeral ligaments. J Shoulder Elbow Surg 5: 249-254, 1996. 44. Mow VC, et al: Material properties of the inferior glenohumeral ligament and the glenohumeral articular cartilage. In FA Matsen, FH Fu, RJ Hawkins, eds: The shoulder: 12. Butler DL, Goldstein SA, Guilak F: Functional tissue engineering: the role of a balance of mobility and stability. Rosemont, IL, 1993, American Academy of biomechanics. J Biomech Eng 122:570-575, 2000. Orthopaedic Surgeons, pp. 29-67. 13. Colachis SC, Strohm BR, Brechner VL: Effects of axillary nerve block on muscle force 45. O’Driscoll SW, Horii E, Morrey BF, Carmichael S: Anatomy of the ulnar part of the in the upper extremity. Arch Phys Med Rehabil 50(11):645-647, 1969. lateral collateral ligament of the elbow. Clin Anat 5:296, 1992. 14. DePalma AF, Callery G, Bennett GA: Variational anatomy and degenerative lesions of 46. Ovesen J, Nielsen S: Posterior instability of the shoulder. Acta Orthop Scand the shoulder bone. AAOS Instruct Course Lect 16:255, 1949. 57(5):436-439, 1986. 15. DePalma AF, Coker AJ, Probhaker M: The role of the subscapularis in recurrent 47. Palmerud G, Forsman M, Sporrong H, Herberts P, Kadefors R: Intramuscular pressure anterior dislocation of the shoulder. Clin Orthop Relat Res 54:35-49, 1969. of the infra- and supraspinatus muscles in relation to hand load and arm posture. Eur J Appl Physiol 83:223-230, 2000. 16. Frost P, Bonde JP, Mikkelson S, Andersen JH, Fallentin N, Kaergaard A, Thomsen JF: Risk of shoulder tendinitis in relation to shoulder loads in monotonous repetitive 48. Patel PR, et al: Anatomy and biomechanics of the coracohumeral and superior work. Am J Indust Med 41:11-18, 2002. glenohumeral ligaments. Trans Orthop Res Soc 21:702, 1996. 17. Fukuda K, Chen CM, Cofield RH, Chao EYS: Biomechanical analysis of stability and 49. Pope MH, Wilder DG: Biomechanics of the shoulder. In M Nordin, GBJ Andersson, fixation strength of total shoulder prostheses. Orthopedics 11:141-149, 1988. MH Pope, eds: Musculoskeletal disorders in the workplace. St. Louis, 1997, Mosby-Year Book, pp. 352-358. 18. Gerber C, Schneeberger AG, Beck M, Schlegel U: Mechanical strength of repairs of the rotator cuff. J Bone Joint Surg 76-B(3):371-380, 1994. 50. Poppen NK, Walker PS: Forces at the glenohumeral joint in abduction. Clin Orthop Relat Res 135:165-170, 1978. 19. Gerber C, Schneeberger AG, Perren SM, Nyffeler R: Experimental rotator cuff repair. J Bone Joint Surg 81-A(9):1281-1290, 1999. 51. Punnett L, Fine LJ, Keyserling WM, Herrin GD, Chaffin DB, et al: Shoulder disorders and postural stress in automobile assembly work. Scand J Work Environ Health 20. Goel VK, Singh D, Bijlani V: Contact areas in human elbow joints. J Biomech Eng 26(4):283-291, 2000. 104(3):169-175, 1982. 52. Regan WD, Korinek BS, Morrey BF, An KN: Biomechanical study of ligaments around 21. Grieco A: Application of the concise exposure index (OCRA) to tasks involving the elbow joint. 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J Bone Joint Surg 72(9):1334-1343, 1990. 56. Sommerich CM, McGlothlin JD, Marras WS: Occupational risk factors associated 25. Herberts P, Kadefors R, Högfors C, Sigholm G: Shoulder pain and heavy manual labor with soft tissue disorders of the shoulder: a review of recent investigations in Clin Orthop Relat Res (198):166-178, 1984. the literature. Ergonomics 36(6):697-717, 1993. 26. Högfors C, Peterson B, Sigholm G, Herberts P: Biomechanical model of the human 57. Soslowsky L J, Flatow EL, Bigliani LU, Pawluk RJ, Ateshian GA, Mow VC: Quantitation of shoulder. II. Shoulder rhythm. J Biomech 24(8):699-709, 1991. in situ contact areas at the glenohumeral joint: a biomechanical study. J Orthop Res 10:524-534, 1992. 27 Högfors C, Sigholm G, Herberts P: Biomechanical model of the human shoulder. I. Elements. J Biomech 20(2):157-166, 1987. 58. Soslowsky L J, Flatow EL, Bigliani LU, Mow VC: Articular geometry of the glenohumeral joint. Clin Orthop Relat Res 285:181-189, 1992. 28. 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Kapandji IA: The physiology of the joints. Volume 1: Upper limb, ed 2. Edinburgh, Neer Award 1999. Overuse activity injures the supraspinatus tendon in an animal 1982, Churchill Livingstone. model: a histologic and biomechanical study. J Shoulder Elbow Surg 9(2):79-84, 2000. 32. Kaptein BL, van der Helm FCT: Estimating muscle attachment contours by transforming geometrical bone models. J Biomech 37:263-273, 2004. 62. Soslowsky L J, Thomopoulos S, Esmail A, Flanagan CL, Iannotti JP, Williamson JD, Carpenter JE: Rotator cuff tendinosis in an animal model: role of extrinsic and 33. Kumar VP, Satku K, Balasubramaniam P: The role of the long head of biceps brachii overuse factors. Ann Biomed Eng 30(8):1057-1063, 2002. in the stabilization of the head of the humerus. Clin Orthop Relat Res 244:172-175, 1989. 63. Speer KP, et al: Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg 76A:1819-1826, 1994. 34. Latko WA, Armstrong TJ, Franzblau A, Ulin SS, Werner RA, Albers JW: Cross-sectional study of the relationship between repetitive work and the prevalence of upper limb 64. Stormont TJ, An KN, Morrey BF, Chao EY: Elbow joint contact study: comparison of musculoskeletal disorders. Am J Indust Med 36:248-259, 1999. techniques. J Biomech 5:329-336, 1985. 35. Malicky DM, Kuhn JE, Frisancho JC, Lindholm SR, Raz JA, Soslowsky LJ: Neer Award 65. Turkel SJ, Panio MW, Marshall JL, Girgis FG: Stabilizing mechanisms preventing ante- 2001. Nonrecoverable strain fields of the anteroinferior glenohumeral capsule under rior dislocation of the glenohumeral joint. J Bone Joint Surg 63A:1208-1217, 1981. subluxation. J Shoulder Elbow Surg 11(6):529-540, 2002. 66. Uhthoff HK, Matsumoto F, Trudel G, Himori K: Early reattachment does not reverse 36. Malicky DM, Soslowsky LJ, Blasier RB, Shyr Y: Anterior glenohumeral stabilization atrophy and fat accumulation of the supraspinatus—an experimental study in rabbits. factors: progressive effects in a biomechanical model. J Orthop Res 14(2):282-288, J Orthop Res 21:386-392, 2003. 1996. 67. van der Helm FCT: A finite element musculoskeletal model of the shoulder mechanism. 37. Malicky DM, Soslowsky LJ, Kuhn JE, Bey MJ, Mouro CM, Raz JA, Liu CA: Total strain J Biomech 27(5):551-569, 1994. fields of the antero-inferior shoulder capsule under subluxation: a stereoradiogram- metric study. J Biomech Eng 123(5):425-431, 2001. 68. Warner JJ, Deng XH, Warren RF, Trozilli PA: Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint. Am J Sports Med 20(6): 38. Martin RB, Burr DB, Sharkey NA: Mechanical properties of ligament and tendon. 675-685, 1992. In RB Martin, DB Burr, NA Sharkey, eds: Skeletal tissue mechanics. New York, 1998, Springer, pp. 309-348. 69. Warner JP, Bowen MK, Deng XH, Hannafin JA, Arnoczky SP, Warren RF: Articular contact patterns of the normal glenohumeral joint. J Shoulder Elbow Surg 7(4): 39. Matsumoto F, Uhthoff HK, Trudel G, Loehr JF: Delayed tendon reattachment does not 381-388, 1998. reverse atrophy and fat accumulation of the supraspinatus—an experimental study in rabbits. J Orthop Res 20:357-363, 2002. 70. Woo SLY, Akeson WH, Jemmott GF: Measurements of nonhomogeneous, directional mechanical properties of articular cartilage in tension. J Biomech 9(12):785-791, 40. Meskers CGM, Vermeulen HM, de Goot JH, van der Helm FCT, Rozing PM: 3D shoul- 1976. der position measurements using a six-degree-of-freedom electromagnetic tracking device. Clin Biomech 13:280-292, 1998.

5cC H A P T E R When occupational activity-related pain is the chief complaint, the usual questions as to the location, timing, and character of Evaluation of the the pain need to be supplemented by a detailed work history. Shoulder and Elbow Exploration into the exact nature of the task and how often it is performed is necessary to further elucidate occupational risk Derek Plausinis and Joseph D. Zuckerman factors that can predispose to or aggravate the current condition. How often and how quickly the task is carried out should be Coordinated movement of the shoulder and elbow is essential to noted. Repetitive work, especially when combined with high force position the hand in space. Symptoms related to the shoulder demands, has been associated with shoulder tendinitis.4 Other and elbow are often vague and clinically difficult to diagnose. work-related risk factors include high force, awkward joint posture, Numerous associated musculoskeletal disorders such as tendini- direct pressure, vibration, and repetitive overhead activities.21 tis and nerve entrapment syndromes have been found to be related to repetitive and forceful use of the upper extremity in A history with documentation of prior claims, time off a wide variety of occupations.4 Because symptoms may overlap, work, and litigation in process constitutes valuable information it is important to distinguish referred pain from the cervical spine because secondary gain can play a significant role in the prog- or adjacent joints from that arising locally. Sound knowledge of nosis. Just as important as the task itself is the mechanical and local anatomy and appreciation of the salient features of the psychologic environment in which it is performed. In addition history and physical examination are crucial to the formulation to the degree of stress involved, the presence of a draft, the need of an accurate diagnosis, treatment regimen, and plan for pre- to work at a height, the positioning of equipment/tools, and vention, especially with regard to work-related injuries. the use of gloves may all play a role in the multifactorial etiol- ogy of repetitive strain disorders. Consideration of how the pres- THE SHOULDER ent condition affects recreation and activities of daily living also assists in determining the severity of the problem. History Localized pain that is intense enough to disrupt sleep and Complaints related to the upper extremity must be approached in cause limitation of simple overhead activities is most commonly an organized methodical manner, with care taken to not focus due to rotator cuff pathology. Infection, arthritis, and frozen too quickly on a specific complaint so as to avoid missing a more shoulder syndrome, however, can less frequently be manifested generalized or related condition. At the initial assessment, identi- in a similar manner. Pain on carrying heavy packages at the side fication of personal and work-related risk factors is essential. The or when pushing a revolving door open may be more indicative patient’s age, hand dominance, occupation, and chief complaint of instability of the glenohumeral joint. should begin every history because these are the major contribu- tors to the establishment of an accurate diagnosis. Age and nature Patients should be questioned with respect to previous injuries of the complaint can be very directive in identifying the underly- and any preexisting conditions that may have predisposed them ing shoulder disorder. A 40-year-old carpenter’s complaint of pain to the current problem. If an acute injury is reported, details of in the overhead position, for example, indicates to the physician its mechanism and the position of the extremity at the time force to evaluate further the possibility of impingement and rotator was applied should be ascertained. In the case of a fall, the cuff pathology, as opposed to a 20-year-old gymnast’s complaint height, the type of surface onto which the patient fell, and the that the shoulder “slips out” in the abducted and externally body part that struck first should be recorded. Feelings of sub- rotated position, which suggests ligamentous instability. luxation or crepitus at the time of injury with an inability to continue working secondary to immediate pain attest to the Symptoms of pain, instability, and loss of motion account severity. In addition, symptoms of numbness or paraesthesia for most complaints about the shoulder. Noting maneuvers that may accompany episodes of instability. The mechanism of ante- provoke pain, presence of night pain, radiation of symptoms, rior shoulder dislocation is usually the result of forced abduction and neck and opposite shoulder pain can aid in differentiating and external rotation of the shoulder, whereas direct trauma is between referred pain and local pathology. Bilateral shoulder more likely to cause contusions or fractures. A fall onto or direct pain that is worsened by hyperextension or rotation of the neck blow to the top of the shoulder often results in varying degrees but not by glenohumeral motion is due most often to cervical of acromioclavicular injury, whereas falls onto the outstretched spine pathology as opposed to an intrinsic shoulder disorder. hand can easily result in proximal humeral fractures. The physician must also ask about the presence of any extremity weakness, radiating pain, or paraesthesia. The distribution of neu- For any injury or joint disorder, treatments undertaken to date rologic symptoms assists in differentiating cervical radiculopathy must be ascertained. These include previous physician consults, from myelopathy or brachial neuritis. medications, physiotherapy, splints, or joint injections. In the shoul- der, multiple steroid injections in the subacromial space may lead to rotator cuff degeneration and tearing.26 Finally, a careful past med- ical history and functional assessment must be obtained. Multiple joint pains may suggest rheumatologic disease or referred pain. Physical examination Even with the most thorough history, the physician may or may not have a clear sense of the underlying problem. A systematic

168 Chapter 5c ● Evaluation of the shoulder and elbow Table 5c.1 Summary approach to shoulder physical Figure 5c.1 Severe axillary nerve palsy manifested as deltoid examination atrophy, squaring off of the shoulder, and inferior subluxation of the humeral head. Cervical spine examination Neurovascular assessment rotator cuff tears, this may be related also to supraspinatus nerve Shoulder examination entrapment neuropathy or C5 nerve root pathology. Prominence of the clavicle may suggest clavicle fracture or malunion as well Inspection as acromioclavicular joint dislocations (Fig. 5c.3). Swelling is Palpation unusual but may be seen in cases of subacromial bursitis or Active and passive range of motion extravasation of synovial fluid in massive rotator cuff tears. Special tests Posterior dimpling or a “sulcus” may suggest anterior shoulder dislocation. Impingement Hawkins test Neer’s test Painful arc Rotator cuff muscles Supraspinatus Infraspinatus and teres minor Subscapularis Biceps tendon Check for rupture Speed’s test Yergason’s test Stability tests Anterior Posterior Inferior and generalized laxity AC joint assessment Local tenderness Cross-body adduction Injection tests AC joint Subacromial space Glenohumeral joint AC, acromioclavicular. Note: see text for detailed description of examination maneuvers. meticulous approach to the physical examination is therefore Figure 5c.2 Supraspinatus and infraspinatus atrophy noted from required to avoid missing subtle findings and arriving at a diag- behind; the atrophy was secondary to a long-standing rotator cuff tear. nosis that is inaccurate or incomplete. A summary of the key elements of the shoulder physical examination is provided in Table 5c.1. Note that evaluation of all potential shoulder prob- lems must include a thorough examination of the cervical spine. Inspection occurs with the patient sitting or standing and appropriately gowned to expose the shoulder entirely. The shoul- der should be examined for signs of asymmetry caused by muscle wasting, soft tissue swelling, or bone or articular incon- gruities and a comparison made with the unaffected side. Muscle spasm involving the trapezius or paracervical muscles may cause asymmetry and may be related to cervical root pathology,8 whereas muscle fatigue may affect shoulder posture and kinemat- ics.9 Deltoid atrophy may be associated with general disuse of the shoulder or related to axillary nerve pathology; best noted from an anterior vantage point, it is characterized by squaring off of the involved shoulder (Fig. 5c.1). Atrophy of the supraspinatus or infraspinatus muscles is best visualized from behind (Fig. 5c.2). Most commonly seen in association with

Chapter 5c ● The shoulder 169 Figure 5c.3 Acromioclavicular separation with complete loss of The American Shoulder and Elbow Surgeons has recom- mended that four planes of shoulder motion be assessed in all articulation of the joint surfaces and prominence of the distal end of patients: total forward elevation, external rotation with the elbow at the side, external rotation with the arm abducted 90 degrees, the clavicle. and internal rotation behind the back.22 Active and passive motion for both shoulders should be recorded. Abduction and internal The next step in a comprehensive examination of the shoulder rotation are best examined with the patient sitting upright on the is palpation of the bony and soft tissue elements. Tenderness or examination table. Forward elevation and external rotation can crepitus about the clavicle suggests fracture or nonunion, partic- most accurately be examined with the patient both upright and ularly if consistent with details of the history. Acromioclavicular supine to ensure that compensatory movements of the spine are joint tenderness is found in cases of arthritis and may be seen in eliminated. A limited active arc of motion may have a mus- those whose occupations require carrying heavy loads on their culotendinous or neurologic etiology, or it may be related to shoulders like lumber or postal bags21 or in the presence of insta- pain. Limited passive motion suggests a mechanical block as bility secondary to traumatic ligamentous disruption. Tenderness in adhesive capsulitis, malunion of fractures, loose bodies, or on palpation over various anatomic landmarks can provide impor- glenohumeral arthritis. When assessing forward elevation, the tant clues leading to a diagnosis: Tenderness of the anterior of practitioner should view the patient from a lateral position and the acromion may be a subtle indicator of rotator cuff impinge- reference the angle of the arm with the posterior thorax. External ment; tenderness about the greater tuberosity may be seen in rotation, both active and passive, is best assessed with the arm cases of rotator cuff tears, supraspinatus tendinitis, or fracture; at the side and the elbow flexed 90 degrees (Fig. 5c.4). A deficiency tenderness over the bicipital groove, which is found between in active external rotation generally indicates neurologic or rota- the greater and lesser tuberosities, is suggestive of bicipital ten- tor cuff derangement, whereas one in both active and passive dinitis; and tenderness over the posterior joint line beneath the external rotation may be seen in adhesive capsulitis or in patients posterior of the acromion may represent glenohumeral arthritis. with mechanical blocks such as locked posterior dislocations. Anterior joint or capsular tenderness is more representative of Testing external rotation with the arm abducted 90 degrees may soft tissue injury after anterior shoulder dislocation or sub- be helpful, particularly in patients performing repetitive over- luxation.8 A nonspecific indicator of inflammation, local head activities such as throwing or welding. In this position, warmth is seen in conditions such as inflammatory arthritides symptoms suggestive of capsulolabral deficiencies, greater or infection. Anesthesia or hypoesthesia in the dermatome over- tuberosity pathology, and instability may be elicited. Internal lying the middle deltoid suggests injury to the axillary nerve rotation is generally tested with the patient sitting upright. The from traction, compression, or demyelination. patient is asked to reach around the back while internally rotat- ing (and slightly extending) the shoulder so as to record the level Both active and passive joint motion must be assessed. It reached by the outstretched thumb. This is commonly docu- is important to understand the two basic components of shoul- mented as the buttock, sacrum, iliac crest, and exact lumbar der elevation: glenohumeral and scapulothoracic. In the first or thoracic spinous process reached. Generally, active and pas- 30 degrees of elevation in the scapular plane, motion occurs sive range of motion in this plane is similar, with limitations mostly at the glenohumeral joint. As the arm is elevated further, again suggestive of subacromial pathology such as rotator cuff more scapulothoracic motion occurs with an equal contribution derangement or a frozen shoulder. of glenohumeral and scapulothoracic movement in the last 60 degrees of elevation. In elevation there is a 2:1 ratio of gleno- Figure 5c.4 External rotation of the glenohumeral joint is assessed humeral to scapulothoracic motion overall.12 To assess the rela- with the patient supine to prevent torso rotation. The elbow is flexed to tive contributions of each, the scapula should be stabilized by 90 degrees with the arm at the side. holding the inferior scapular angle. Adhesions or rotator cuff derangement likely alters the normal fluid pattern of gleno- humeral motion, and a greater proportion of the arc of motion becomes scapulothoracic.

170 Chapter 5c ● Evaluation of the shoulder and elbow Table 5c.2 Muscle grading Muscle gradations Description 5 (normal) Complete ROM against gravity with full resistance 4 (good) Complete ROM against gravity with some resistance 3 (fair) Complete ROM against gravity 2 (poor) Complete ROM with gravity eliminated 1 (trace) Evidence of muscle contraction; no joint motion 0 (absent) No contractility ROM, range of motion. Muscle strength testing is essential to assess the competence Figure 5c.5 To test for teres minor involvement in rotator cuff of the musculotendinous complexes about the shoulder and to identify possible peripheral or central neuropathology such as disorders, support the patient’s arm at 90 degrees of elevation in the peripheral compressive neuropathy or cervical stenosis. In this regard, a thorough understanding of the structure of the brachial scapular plane and ask the patient to externally rotate against plexus and innervation patterns more peripherally is critical. Clearly, a suggestion of cervical pathology stimulates a more resistance. The inability to externally rotate the arm indicates a thorough neurologic examination. Muscle strength should be recorded using the universal system of grading on a scale from positive “horn blower’s” sign. 0 to 5, with the opposite and presumably normal limb used as the control for comparison (Table 5c.2). It is important to cuff tears often produce a discrepancy between active and passive realize that in the presence of pain, the accuracy of motor motion. The “dropping sign” is demonstrated by grasping the strength recording may be called into question. forearm with the elbow flexed and held at the side and passively externally rotating the shoulder 45 degrees. The patient is asked The primary motor functions—forward flexion, abduction, to resist a force in external rotation as the forearm is released. and external and internal rotation—are tested by resisting the If the patient is unable to hold the arm in this position and the particular plane of motion. Forward flexion is primarily the role forearm drops to a neutral position, then the “dropping sign” is of the anterior head of the deltoid muscle (axillary nerve, C5-C6) positive for infraspinatus weakness.9 Further extension of a rota- with secondary flexors, including the biceps and coracobrachialis tor cuff tear into the teres minor can be suggested by external muscles (musculocutaneous nerve, C5-C7), and the clavicular rotation weakness in abduction. This is tested by supporting portion of the pectoralis major muscle (lateral pectoral nerve, the patient’s arm at 90 degrees of elevation in the scapular plane C5-C6). Abduction tests the strength of both the middle third and then asking the patient to externally rotate against resistance of the deltoid muscle (axillary nerve, C5-C6) and the supraspina- (Fig. 5c.5). If the patient cannot externally rotate, then a “horn- tus muscle (suprascapular nerve, C5). Finally, the presence of blower’s” sign is present,27 indicating extension of a tear into the scapular winging should be noted, indicating dysfunction of the teres minor. This sign can be functionally illustrated by asking serratus anterior (long thoracic nerve, C5-C7) or the trapezius the patient to bring the hand to the mouth; patients with infra- (spinal accessory nerve). Scapular winging may be demonstrated spinatus and teres minor cuff weakness will abduct the arm to by inspecting from behind while asking the patient to push against accommodate for inability to externally rotate. a wall. The subscapularis cannot be isolated by testing internal For assessing the rotator cuff, the key clinical features are rotation strength with the arm at the side but rather requires the muscle strength and pain. Whereas weakness alone may suggest “lift-off ” test,6 which involves asking the patient to place his or a compressive neuropathy, that accompanied by pain suggests her hand behind the back at the lumbosacral junction and then rotator cuff pathology. Before formal cuff muscle testing, the lift the hand off. Inability to perform a lift-off suggests sub- presence of any muscular atrophy is first noted (Fig. 5c.1). The scapularis rupture; many patients with shoulder stiffness, how- greater tuberosity is palpated for tenderness or defect at the site ever, are unable to perform this maneuver. The examiner must of insertion of the supraspinatus, and the shoulder is passively pay attention to the elbow during the lift-off test, because flexed and extended while palpating for subacromial crepitus. patients with subscapularis deficiency may give the false impres- The strength of the supraspinatus muscle may be isolated by sion of being able to lift off by extending the elbow. When elevating the arm 90 degrees, maximally pronating the forearm patients have limited internal rotation and the ability to perform with the thumb down, and applying a downward force on the the lift-off test is compromised, the subscapularis may be tested patient’s arm.24 The supraspinatus is affected in most rotator cuff with the “belly press,”5 which involves asking the patient to place tears, and when extension into the infraspinatus tendon occurs, his or her hand on the abdomen and then bring his or her elbow external rotation may be weak or painful. forward to the level of the hand. Patients with subscapularis insufficiency will keep their elbow at the side with the wrist External rotation strength with the elbow at the side assesses flexed and will be unable to effectively bring the elbow forward. principally the infraspinatus muscle (suprascapular nerve, C5-C6) and teres minor muscle (axillary nerve, C5-C6). Large rotator

Chapter 5c ● The shoulder 171 Figure 5c.6 Positive impingement sign as described by Neer with forced forward elevation of the arm, causing the supraspinatus to impinge on the undersurface of the acromion. Several provocative tests can be used to elucidate subacro- Figure 5c.7 Anterior instability is tested by placing the shoulder in mial impingement, of which two have been classically used. The 90 degrees of abduction and external rotation while attempting to level Neer “impingement sign” consists of forced forward elevation of the humeral head out anteriorly with gentle posterior pressure. the arm.13 Pain is elicited as the inflamed supraspinatus tendon Apprehension and pain are indicative of positive responses. impinges against the inferior border of the acromion anterior (Fig. 5c.6). If local anesthetic is administered to the subacromial A posteriorly directed force is applied to the proximal humerus, space, pain in impingement syndrome is eliminated, which then and in cases of instability pain or apprehension is relieved, indi- confirms a positive impingement test.13 The impingement sign cating a positive “relocation” test.25 A similar but more provoca- becomes much less reliable, however, when there is a limitation tive test for anterior instability is to abduct and externally rotate of passive forward elevation. In the Hawkins impingement test, the shoulder in the upright position. When an anteriorly the arm is forward-flexed 90 degrees and then forcibly internally directed force is applied to the posterior proximal humerus, rotated. Pain is evoked as the inflamed supraspinatus tendon the patient with anterior instability becomes apprehensive or is impinged against the coracoacromial ligament. In addition to experiences pain in the shoulder (Fig. 5c.7). these impingement tests, patients with impingement often demonstrate a “painful arc.” As the arm is abducted in the Although less common, posterior instability may be seen coronal plane, pain occurs between 60 and 100 degrees and is after a traumatic event or in association with a history of seizure usually maximal at 90 degrees. Patients may be observed to disorder or alcohol abuse. A “posterior apprehension test” may rotate the humerus externally in the abducted position to mini- be performed by flexing and internally rotating the shoulder and mize impingement of the greater tuberosity under the acromion. noting if the patient experiences a sense of instability. To further assess posterior laxity, an axial load can be applied to the elbow Assessment of the acromioclavicular joint begins with exami- with the shoulder flexed 90 degrees and in neutral rotation. nation for local tenderness and swelling. A provocative maneu- This maneuver subluxes the humeral head posteriorly. The exam- ver for acromioclavicular joint pathology, cross-body adduction, iner then abducts the arm and palpates for the sudden reduction can be elicited by passively elevating the arm to 90 degrees and of the subluxed shoulder.8 adducting the arm and forearm across the chest. Pain near the acromioclavicular joint with cross-body adduction indicates Anterior and posterior capsular laxity may be examined further acromioclavicular joint pathology,3 whereas that in the posterior by assessing the amount of glenohumeral translation. This may shoulder usually results from posterior capsular tightness. In patients with documented or suspected glenohumeral instability, anterior instability is the most common clinical presentation. The simplest clinical maneuver, the “apprehension test,” is performed with the patient in the supine position with the arm abducted 90 degrees. The shoulder is externally rotated as the patient’s facial expression is noted. A patient’s appre- hension or sense of impending shoulder subluxation or disloca- tion indicates a positive test. The “relocation” test can then be performed with the shoulder at the point of apprehension.

172 Chapter 5c ● Evaluation of the shoulder and elbow be difficult to produce on examination without the benefit of The long head of the biceps is first assessed by examining anesthesia but should be assessed in all patients. Humeral head for continuity of the tendon. The patient is asked to resist gen- translations may be tested with the patient sitting upright or tle flexion of the elbow, and the upper arm is inspected. An lying supine while the scapula is stabilized with one hand and abrupt change in contour of the biceps muscle proximally that is the humeral head grasped with the other. Anterior and posterior asymmetric with the contralateral side, referred to as a “Popeye” translatory loads are applied to evaluate anterior and posterior muscle, indicates rupture of the long head of the biceps. With instability, respectively. The humeral head normally translates an intact biceps tendon, tenderness in the bicipital groove is a posteriorly up to 50% of the width of the glenoid, but the shoul- common finding in bicipital tendinitis. As the humerus is exter- der does not appreciably translate anteriorly. It is important to nally rotated, the anterior pain of bicipital tendonitis typically compare these findings with those in the opposite shoulder moves more laterally with the externally rotated bicipital groove. because some degree of laxity may be expected even in normal shoulders. Common provocative maneuvers for long head of biceps pain include Yergason’s test and Speed’s test. Yergason’s test con- Patients with inferior instability may have their symptoms sists of actively supinating the forearm against examiner resist- reproduced by applying longitudinal downward traction on ance with the elbow flexed 90 degrees. Speed’s test involves the arm. When the deltoid muscle is relaxed, an inferior “sulcus forward elevation of the arm against resistance with the elbow sign” is usually present in affected patients (Fig. 5c.8). Patients extended and the forearm supinated. If positive, both tests elicit with inferior instability commonly also have anterior and pos- pain in the region of the bicipital groove. It should be noted terior instability, in which case the term multidirectional insta- that this diagnosis is often a component of the impingement bility is used. This condition is usually associated with syndrome, and controversy exists as to whether it exists as an generalized hyperlaxity as evidenced by hyperextension of the isolated entity. elbows and knees or the ability for the patient to bring the thumb passively to touch the ipsilateral forearm. In addition to the detailed neurologic examination outlined earlier, a careful vascular examination should be performed to rule out vascular compression in the neck as the source of clau- dicant shoulder pain, the so-called thoracic outlet syndrome. Distal pulses should routinely be palpated. Several tests have a time-honored role in the diagnosis of vascular insufficiency, perhaps the most commonly used of which is Adson’s maneuver or one of its several modifications. The examiner palpates the radial pulse and abducts the ipsilateral arm 90 degrees while extending and externally rotating the shoulder with the patient turning the head to the opposite side. A diminishing peripheral pulse signifies proximal compression and indicates a positive test. It is critical to identify the source of vascular compression, including an accessory rib, Pancoast’s tumor, fibrous bands, or clavicular malunion, so that proper steps in management may be taken. Figure 5c.8 Inferior ligamentous laxity exhibited by an inferiorly Diagnostic testing subluxed humeral head with downward traction on the humerus with the arm at the side. The practitioner generally establishes the diagnosis after a thor- ough history and comprehensive physical examination. Most imaging tests are performed to confirm the physician’s clinical impression, but inevitably in some cases the diagnosis remains unclear and further investigation is warranted. The mainstay of imaging remains the standard radiograph. In general, all patients with complaints referable to the shoulder should receive a routine series of at least three radiographs as initial screening. This consists of anteroposterior (AP), scapular lateral, and axillary radiographs of the shoulder with the beam centered over the glenohumeral joint. When shooting these radiographs it is important to follow meticulous guidelines and to keep in mind that the plane of the scapula is rotated anteri- orly approximately 35 to 40 degrees (Fig. 5c.9). A true AP radi- ograph in the scapular plane is taken with the posterior aspect of the affected shoulder against the cassette and the opposite shoulder rotated anteriorly approximately 40 degrees. The AP radiograph in internal rotation shows the greater tuberosity en face, external rotation shows it in profile, and both show

Chapter 5c ● The shoulder 173 A B C Figure 5c.9 Technique for obtaining scapular anteroposterior (A), lateral (B), and axillary (C) views of a trauma series required on all patients. different aspects of the humeral head. In these views the distance key projection for identifying shoulder dislocations and any asso- between the humeral head and the acromion process should be ciated anterior glenoid avulsion fractures (bony Bankart lesion) or assessed. In cases of massive rotator cuff tears, the normal inter- posterior impression fractures of the humeral head (Hill-Sachs space, averaging 10 mm, may diminish as the humeral head lesion) (Fig. 5c.12). The relative position of the anterior aspect of migrates cephalad, and a break in the inferior calcar line may be the acromion with respect to the clavicle should be assessed, par- seen (Fig. 5c.10).7 Also considered routine in trauma situations ticularly in cases of impingement syndrome. Anterior projection is the scapular lateral view, in which the scapula is seen tangen- of the acromion beyond the anterior limits of the clavicle has been tially. This is an anterior oblique projection taken with the shown to predispose to rotator cuff problems.28 patient rotating the involved shoulder 60 degrees toward the central beam.7 Its value lies in identifying shoulder dislocations The “outlet view” represents a lateral projection into the and fractures of the humeral head or neck or scapula. subacromial space. It is an ideal projection for assessing the slope of the acromion, which has been shown to have an impact on In the axillary view, the patient is positioned supine with the the development of impingement syndrome (Fig. 5c.13). It is arm abducted. A horizontal x-ray beam is directed in toward taken with the patient standing and the affected shoulder the axilla. This projection visualizes the relationship between the rotated 60 degrees toward an x-ray beam angled 10 to 15 degrees humeral head, glenoid, coracoid, and acromion (Fig. 5c.11). It is a caudad.7

174 Chapter 5c ● Evaluation of the shoulder and elbow Figure 5c.12 Locked posterior dislocation with a humeral head impression fracture. Figure 5c.10 In the presence of massive rotator cuff tears, a high- tissue pathology about the shoulder. Multiaxial images and the riding humeral head is noted with decreased acromiohumeral distance development of newer MRI protocols have enabled more accu- and a break in the inferior calcar margin. rate assessments of shoulder pathology. For rotator cuff pathol- ogy and impingement syndrome, MRI can identify rotator A specialized AP radiograph angled 15 degrees cephalad is a cuff tendinosis and partial and full thickness tears (Fig. 5c.14).1 valuable tool for imaging the distal and middle aspects of the An estimate of rotator cuff tear size can be made, and the pres- clavicle and acromioclavicular joint. As such, this projection is ence of fatty degeneration of the rotator cuff muscles can be used to assess clavicle fractures, acromioclavicular joint sprains, identified. In cases of impingement, MRI can also identify arthritis, or spurring (a source of rotator cuff impingement), or potential sources of cuff impingement such as an osteophyte distal clavicle osteolysis (common in weight lifters). Magnetic resonance imaging (MRI) has become the imaging modality of choice in most centers for identifying most soft C H AC G A Figure 5c.11 Axillary view of the shoulder, crucial for determining the Figure 5c.13 Supraspinatus outlet view with a large subacromial position of the humeral head in relation to the glenoid. The labeled spur, causing impingement. structures are the humeral head (H), glenoid (G), coracoid (C), acromion (A), and acromioclavicular joint (AC).

Chapter 5c ● The shoulder 175 A AC RT SS GT Figure 5c.15 Arthrogram documenting a full-thickness rotator cuff tear with dye extravasation into the subacromial space and laterally to the greater tuberosity. Figure 5c.14 Magnetic resonance image of the right shoulder Although it has largely been replaced by MRI and ultra- sound, arthrography continues to have a role in the diagnosis of revealing a full-thickness rotator cuff tear (RT) with a retracted shoulder disorders. It entails injection of either contrast alone or contrast followed by the injection of room air into the gleno- supraspinatus tendon (SS) underneath the acromion (A) and humeral joint. Various x-ray views are then taken to assess differ- ent shoulder components. The technique has a time-honored acromioclavicular joint (AC). The greater tuberosity (GT) is also shown. role in the diagnosis of complete rotator cuff tears (Fig. 5c.15). The arthrogram may be used also to visualize the long head from the undersurface of the acromioclavicular joint, acromio- of the biceps tendon, thereby diagnosing rupture, tenosynovitis, clavicular joint hypertrophy, or a downward-beaking acromion or subluxation. that may be associated with a subacromial spur. Computed tomography (CT) is used primarily to assess bony In cases of instability when the diagnosis is unclear, MRI pathology further when details are unclear from plain radi- can be used to detect capsular injury or redundancy as well as ographs, as may be seen in cases of recurrent instability with labral tears. Although infrequent, in cases of violent traumatic glenoid or humeral head defects. anterior shoulder dislocations, the subscapularis tendon may be torn either directly off its insertion on the lesser tuberosity or Lidocaine injection tests serve a vital role with regard to in its mid-substance. In the latter case, MRI potentially shows problems of the shoulder in that they can be valuable diagnostic retraction at the site of the tear, or in chronic cases calcific tools when the precise diagnosis is in question. For instance, at deposits may be seen in the substance of the subscapularis mus- times it may be difficult to localize the source of symptoms to cle or tendon. The tendon of the long head of the biceps can be the acromioclavicular joint, the subacromial space, or the gleno- imaged on axial cuts as it sits in the bicipital groove. Absence of humeral joint. In these situations, selective lidocaine injection the tendon in this landmark would imply rupture and subsequent can be of obvious benefit. The subacromial space is the most retraction (which should be obvious on clinical examination) or frequently injected region. Amelioration of symptoms points to subluxation, as may be seen in a congenitally shallow bicipital rotator cuff tendinitis or tear as the culprit; conversely, if symp- groove or after trauma. Bicipital tendinitis is often a more prox- toms persist, the source of pain is elsewhere, although the sub- imal phenomenon and is difficult to image by MRI. Finally, acromial space may be responsible at least in part. Various MRI has a role in the diagnosis of osteonecrosis of the humeral techniques for injection have been described; nevertheless, it is head and should be considered in certain high-risk conditions always important to follow strict sterile technique to minimize such as sickle cell disease, steroid use, or alcohol abuse or in the risk of infection. The subacromial space can be injected deep sea divers in the setting of shoulder pain even without from a lateral approach with relative ease (Fig. 5c.16). Downward radiographic findings. traction may be applied to the arm to help widen the interval between the humeral head and the acromion. Also a frequent Historically regarded as unreliable, ultrasonography has played source of pain, the acromioclavicular joint is easily palpated an increasing role in rotator cuff diagnoses in recent years. With between the distal clavicle and the acromion, with a needle newer equipment and experienced ultrasonographers, sensitivi- directed from its superior aspect. Often, pathology in this joint ties and specificities of 94% or greater for the detection of full- is associated with impingement of the rotator cuff, and selective thickness tears and 93% or greater for partial-thickness tears injection here may help clarify the severity of the referred pain. have been reported.23 Although it has a lower cost than MRI and is a noninvasive test, the availability of accurate rotator cuff assessment is limited by the availability of an experienced mus- culoskeletal ultrasonographer.

176 Chapter 5c ● Evaluation of the shoulder and elbow Figure 5c.16 Subacromial lidocaine injection test via a lateral approach is extremely valuable in the diagnosis of impingement. Technetium bone scanning has a limited role in the evaluation Figure 5c.17 Lateral view demonstrating a spur off the tip of the of problems related to the shoulder. However, it may be of use in the evaluation of adhesive capsulitis or in ruling out occult olecranon. infection, tumor, or avascularity in the presence of persistent symptomatology. Electromyographic and other nerve conduc- immobilization after injury. Elbow stiffness may or may not be tion studies have a definite role in distinguishing central from associated with pain, and it is important to delineate whether the peripheral neuropathy and in investigating the possibility of a patient’s primary concern and source of functional impairment neural basis of muscle wasting or weakness when intrinsic is pain or stiffness. myotendinous pathology is ruled out. Degenerative joint disease ultimately results in activity-related In suggestive cases, shoulder evaluation may include laboratory pain, usually first occurring near full extension. Osteoarthritis studies, particularly routine blood tests such as a complete blood may present also with a history of episodic sharp pain in the count, erythrocyte sedimentation rate, C-reactive protein, rheuma- elbow and intermittent loss of motion or locking. These mechan- toid factor, antinuclear antibody, and blood chemistry analysis, ical symptoms commonly arise also after a traumatic event to the to exclude inflammatory arthritides or infection. Additionally, elbow and suggest the presence of loose bodies that usually adhesive capsulitis is more likely in diabetic patients, hence require surgical removal. the importance of assessing serum glucose levels. If joint sepsis or crystal diseases are suspected, the glenohumeral joint can be Patients may notice swelling about the elbow joint. A joint aspirated and fluid sent for Gram stain, culture, cell count, and effusion or synovitis is present with some diffuse swelling about microscopy for crystals. the elbow and is often more apparent clinically in the postero- lateral aspect. In contrast, olecranon bursitis may present with THE ELBOW a recurrent mass directly over the olecranon. Bone spurs off the olecranon (Fig. 5c.17) have been associated with olecranon History bursitis (Fig. 5c.18), and the patient may have noticed the devel- opment of a more prominent olecranon. Olecranon bursitis The approach to the history for the patient with an occupational may be sterile or septic, and the patient should be questioned as elbow disorder follows an outline similar to that for a shoulder to a history of fever, erythema, previous attempts at aspiration, disorder. The general content for history of present illness and and drainage. occupational history are as outlined previously. Specific com- plaints arising from elbow pathology with clinical examples are Unlike the shoulder, recurrent instability is an uncommon provided below. problem in the elbow. Stiffness is the usual problem after elbow dislocation. When present, instability may present as recurrent Symptoms related to the elbow usually involve pain or episodes of dislocation or more commonly as a sense of elbow stiffness. Whereas pain is a common complaint with advanced subluxation and pain. In cases of recurrent instability after elbow elbow arthritis, the early phases of degenerative joint disease in trauma, symptoms are most likely to occur from lateral ligament the elbow usually present with loss of motion as the primary deficiency and are provoked by activities where a valgus stress is concern. After any trauma to the elbow, stiffness is also a applied to the elbow with the forearm in supination. The valgus common complaint, particularly with a history of prolonged instability from medial collateral ligament laxity is typically seen in throwing athletes and very uncommonly as a result of workplace injury.

Chapter 5c ● The elbow 177 Figure 5c.18 Classic appearance of olecranon bursitis. Note the Inspection of the elbow is first undertaken to look for any signs of inflammation or previous injury. To identify subtle findings, prominent fluid-filled bursa over the olecranon (compared with a normal comparison with the unaffected side is helpful. An elbow effusion may be clinically apparent by a fullness in the posterolateral aspect, elbow in Fig. 5c.19). whereas olecranon bursitis presents with a local mass over the ole- cranon (Fig. 5c.18). With the elbow in full extension and the fore- Tendinopathy about the elbow is a common problem, usually arm in supination, the alignment of the ulna compared with presenting as medial or lateral epicondylitis. Patients typically humerus (carrying angle) is estimated. Despite considerable varia- complain of pain in the region of the flexor or extensor origin tion among individuals, normal values for the carrying angle are that is aggravated with repetitive active wrist movement. Chronic approximately 10 degrees for men and 13 degrees for women.19 tendinitis of the distal biceps tendon is uncommon; however, Childhood injuries to the elbow commonly result in alteration of ruptures may occur after resisted activity, typically in the domi- the carrying angle into either valgus or varus malalignment. nant arms of men in their forties. Although excess valgus alignment may lead to ulnar nerve irrita- tion,17 varus malalignment, also termed a gunstock deformity, is Entrapment neuropathies about the elbow must be consid- usually not associated with any functional deficits. ered also as a possible source of elbow pain and may present with weakness or sensory changes in the hand and wrist as well. Palpation of the elbow relies first on establishing the appro- Lying posterior to the medial epicondyle, the ulnar nerve is prone priate surface anatomy. On the lateral aspect, three important to compression and irritation with activities requiring recurrent bony landmarks appear: lateral epicondyle, radial head, and tip elbow flexion or from direct compression over the nerve. In of the olecranon (Fig. 5c.19). The radial head is a bony promi- cases of cubital tunnel syndrome (ulnar nerve entrapment at nence just distal and slightly inferior to the lateral epicondyle. the elbow), patients typically complain of sensory changes in The location of the radial head is confirmed by rotating the fore- the ring and small fingers. The ulnar nerve lies close to the ulno- arm with the elbow held at 90 degrees of flexion; the rotation of humeral joint and in cases of arthritis can be prone to irritation the radial head on the stationary capitellum is palpable. At the from osteophytes and loose bodies.17 Median and radial nerve center of these three bony landmarks (Fig. 5c.19), fullness indi- compression at the elbow level may occur also, although less fre- cates synovitis or effusion and represents also a safe location for quently than ulnar nerve entrapment. Patients typically present elbow joint aspiration or injection. The radiocapitellar joint may with elbow pain, and neurologic symptoms are less common.19,20 be palpated between the radial head and the lateral epicondyles. When considering the diagnosis of peripheral nerve entrapment, While palpating over this region, passive forearm rotation and the distribution of symptoms and the exacerbating features passive flexion and extension allow for an assessment of any are critical to help determine whether the symptoms are truly crepitus or soft tissue snapping from the radiocapitellar joint. originating at the elbow level or whether referred pain from the shoulder or a cervical radiculopathy may be the underlying cause. On the medial side of the elbow, the medial epicondyle and the olecranon may be identified. In the groove posterior to the medial epicondyle lies the ulnar nerve, which may be gently palpated. Medial to the ulnar nerve is the medial aspect of the ulnohumeral joint. Placing the examining index finger and thumb on either side of the ulna just distal to the olecranon while the elbow is gently flexed and extended allows for the assessment of ulnohumeral joint crepitus and tenderness. Physical examination E R As in the case of shoulder examination, a thorough elbow exam- ination begins with an evaluation of the cervical spine. Shoulder O and wrist examination must be performed also to rule out a referred etiology for the current complaint. In addition, the Figure 5c.19 Lateral side of elbow illustrating the palpable bony complete upper extremity examination will reveal any other landmarks: lateral epicondyles (E), radial head (R), and olecranon (O). disabilities from joints above or below the elbow that may contribute to the patient’s functional deficit.

178 Chapter 5c ● Evaluation of the shoulder and elbow Tendons about the elbow are then systematically palpated. the varus stress and examine the lateral joint line. Recurrent Each tendon should be palpated for continuity on active con- instability occurs very infrequently after elbow dislocations, and traction of the corresponding muscle group. The presence the specific tests for the lateral ligament complex are well of local tenderness, pain with resisted activity, and pain with described.14 These tests are rarely important, however, in the passive stretch of a tendon suggests tendinopathy. For example, setting of occupational elbow disorders. the common extensor origin is just distal to the lateral epi- condyle. Local tenderness, pain with resisted active wrist exten- At elbow level the ulnar, radial, and median nerves may all be sion, and pain with passive wrist flexion all suggest a diagnosis compressed. A detailed assessment of ulnar, radial, and median of lateral epicondylitis (tennis elbow). Similarly, pain over the motor and sensory function, including inspection of the hand common flexor-pronator origin just distal to the medial epi- and forearm for muscle atrophy or fasciculations, should be condyle along with pain with resisted active wrist flexion and performed. The ulnar nerve is palpated behind the medial epi- passive wrist extension suggest medial epicondylitis (golfer’s condyle and once identified, the elbow can be brought from a elbow). After examining the common flexor and extensor ori- position of extension to flexion to determine whether the ulnar gins, the triceps tendon is examined. The triceps tendon inserts nerve subluxes or dislocates anteriorly during flexion. Gently into the olecranon, and palpation may reveal a prominent trac- tapping over the nerve may produce paresthesia radiating into tion spur (Fig. 5c.17). The distal biceps tendon can then be iden- the small finger and ulnar half of the ring finger (Tinel’s sign tified in the middle of the antecubital fossa just lateral to the at the cubital tunnel), indicating nerve irritation. A further sign brachial artery. The biceps assists in elbow flexion and is also the of ulnar nerve compression at the elbow is to hold the joint in primary muscle responsible for forearm supination. A ruptured a flexed position for 1 minute and observe for the development distal biceps tendon (reverse Popeye sign) can be identified by of paresthesias or numbness in the ring and small fingers.17 having the patient perform resisted supination with the elbow in a flexed position and noting a lack of palpable tendon in Less commonly, the median and radial nerves may be com- the cubital fossa. Another symptom is a prominent bulge of the pressed at elbow level.19,20 The median nerve runs adjacent distal aspect of the biceps muscle. to the brachial artery in the antecubital fossa and may be sensi- tive to pressure in the antecubital space or over the proximal por- The elbow is then taken through both active and passive tion of the pronator teres.20 Gentle tapping over the course movements so that range of motion can be documented. Any of the median nerve may produce Tinel’s sign at the point of irri- crepitus from the ulnohumeral or radiocapitellar joints is noted. tation. Compression in the antecubital space (at the lacertus In addition to flexion and extension, forearm rotation must also fibrosis) is tested by actively supinating the forearm against be documented. Limitation of motion or pain on forearm rota- resistance with the elbow flexed beyond 120 degrees. For eval- tion mandates a detailed wrist examination to rule out any uating median nerve compression at the pronator teres, resis- pathology at the distal radioulnar joint. Normal elbow range of ted pronation is performed with the elbow in extension. motion is from full extension (0 degrees) to 145 degrees of flex- Compression of the median nerve may occur also as it travels ion. Normal forearm rotation is from 75 degrees of pronation to under the flexor digitorum superficialis as can be determined 85 degrees of supination.2 For a patient to perform most activities with resisted flexion of the long finger.20 For radial nerve entrap- of daily living, range of motion from 30 degrees to 130 degrees ment, Tinel’s sign along its course may likewise be elicited. of flexion and forearm rotation from 50 degrees of pronation to Perhaps the most important point of examining for radial nerve 50 degrees of supination (i.e., 100 degrees of flexion-extension entrapment is the location of the pain. Pain emanating from and a 100-degree arc of forearm rotation) is necessary.11 radial compression is often associated with tenderness approxi- mately 4 to 5 cm distal to the lateral epicondyle, whereas the Stability testing of the elbow can be challenging, but in the pain of lateral epicondylitis is present adjacent to the lateral setting of occupational disorders elbow instability is an infre- epicondyle.15 quent finding. One of the challenges of instability testing is that valgus and varus stability tests require rotationally stabilizing Diagnostic testing the humerus. From full extension to 20 degrees of flexion the collateral ligaments cannot be isolated, because bony contribu- Routine diagnostic studies for elbow disorders begin with plain tions to stability are provided by the seating of the olecranon in radiographs. A standard elbow series consists of an AP (Fig. 5c.20), the olecranon fossa. Medial collateral ligament laxity has been a lateral (Fig. 5c.17), and an oblique film.18 With a history of shown to be greatest with the elbow in 20 degrees of flexion and trauma, it is particularly important to confirm that the radial the forearm pronated.16 To test the medial collateral ligament, head is in joint as evidenced by its lining up with the capitellum the elbow is held flexed approximately 20 to 30 degrees with the on all views. At the same time, any radial head deformity should forearm pronated and the arm maximally externally rotated as a be noted, as well as signs of radiocapitellar degenerative changes. valgus stress is applied. The presence of medial-sided pain and A radial head view can be requested also if the radial head palpable medial joint line opening are signs of medial collateral cannot be adequately assessed (Fig. 5c.21). The ulnohumeral pathology. Another test to stress the medial collateral ligaments joint can then be studied on the radiographs. In cases of degen- is the “milking sign” performed by fully flexing the patient’s erative joint disease, osteophyte formation medially or laterally elbow and grasping the thumb to apply a valgus stress to the off the ulnohumeral joint is a common finding on the AP view, elbow. The test is positive if medial elbow pain is elicited. and the lateral view may demonstrate osteophytes off the coro- noid or tip of the olecranon. In cases where pathology about Varus stability is tested also with the elbow at 20 to 30 degrees the olecranon is suspected or if loose bodies are a possibility, an of flexion but instead requires maximum internal rotation of the arm. The examiner can then stand behind the patient to apply

Chapter 5c ● The elbow 179 O T LE ME Figure 5c.20 Standard anteroposterior radiograph of the elbow. Figure 5c.22 Axial view of elbow showing the olecranon (O), trochlea Figure 5c.21 Radial head view. of the distal humerus (T), medial epicondyle (ME), and lateral epicondyle (LE). axial view of the flexed elbow can be helpful (Fig. 5c.22). For cases of suspected medial and lateral instability, stress views demonstrate abnormal joint widening. When in doubt, compar- ison views of the unaffected side can be obtained. A complete interpretation of standard radiographs should also include an assessment of soft tissue shadows for signs of swelling or effusion. Seen with cases of elbow effusion, a radi- olucent area posterior to the olecranon fossa represents visu- alization of the posterior fat pad. Anteriorly, it is normal to see a thin concave radiolucent fat pad; however, a convex fat pad known as a “sail sign” indicates an elbow effusion. CT is often helpful in the setting of trauma to identify osseous loose bodies (Fig. 5c.23) or for cases where the osseous anatomy is unclear on standard radiographs.10 Offering the benefit of soft tissue assessment, MRI is ideal for evaluating cases of suspected cartilaginous loose bodies, assessment of tendons when the clinical examination is unclear, assessment of collateral ligaments, or evaluation of soft tissue masses.10,18 It is helpful also in cases of peripheral nerve compression by suspected soft tissue masses such as cysts within the cubital tunnel or synovitis extending into the radial tunnel. Proliferative synovial disorders presenting as an isolated synovitis of unknown etiology are also well suited to MRI evaluation. Although less commonly used in elbow disorders, ultrasound is useful to evaluate fluid collections around the joint and to assess the continuity of superficial muscle tendon units such as the triceps and biceps when the clinical examination is uncer- tain. It has been used also to investigate for intraarticular loose bodies10; however, because ultrasound requires an experienced ultrasonographer, it is less commonly used than CT or MRI in that setting. Electrodiagnostics can be particularly useful in the patient with neurologic symptoms or signs. Electromyography and nerve conduction studies are particularly useful to determine the presence, location, and extent of peripheral nerve compression

180 Chapter 5c ● Evaluation of the shoulder and elbow should be carried out in suspected cases of infection or for isolated effusions of unknown etiology. REFERENCES Figure 5c.23 Computed tomography showing a bony loose body in 1. Bencardino JT, Garcia AI, Palmer WE: Magnetic resonance imaging of the shoulder: the olecranon fossa. rotator cuff. Top Magn Reson Imag 14(1):51-67, 2003. or to identify a brachial plexus lesion or cervical radiculopathy. 2. Boone DC, Azen SP: Normal range of motion of joints in male subjects. J Bone Joint Electrodiagnostic studies for cubital tunnel syndrome and poste- Surg 61A:756-759, 1979. rior interosseous nerve compression syndrome often demonstrate electrophysiologic abnormalities and are helpful to confirm the 3. Chen AL, Rokito AS, Zuckerman JD: The role of the acromioclavicular joint in diagnosis.15,17 In contrast, electrodiagnostic studies in cases of impingement syndrome. Clin Sports Med 22:343-357, 2003. radial tunnel syndrome and pronator syndrome are usually normal.19,20 4. Frost P, Bonde JP, Mikkelsen S, et al: Risk of shoulder tendinitis in relation to shoulder loads in monotonous repetitive work. Am J Indust Med 41(1):11-18, 2002. Diagnostic blocks about the elbow are much less common than for assessment of shoulder disorders but may on occasion 5. Gerber C, Hersche O, Farron A: Isolated rupture of the subscapularis tendon. J Bone be useful. Local anesthetic injection into the radial tunnel distal Joint Surg 78A:1015-1023, 1996. to the lateral epicondyles may help to distinguish cases of radial tunnel syndrome from lateral epicondylitis.15 Similarly, 6. Gerber C, Krushell RJ: Isolated rupture of the subscapularis tendon: clinical features a local anesthetic block may be used at a potential site of median in 16 cases. J Bone Joint Surg 73B:389-394, 1991. nerve compression at the elbow to determine whether it is respon- sible for the patient’s pain.20 7. Gold RH, Bassett LW: Disorders of the shoulder: plain radiographic diagnosis. In LL Seeger, ed: Diagnostic imaging of the shoulder. Baltimore, 1992, Williams & Wilkins. Although less commonly used for elbow disorders, technetium bone scanning may be useful to identify biologically active areas 8. Hawkins RJ, Bokor DJ: Clinical evaluation of shoulder problems. In CA Rockwood Jr, of bone in cases of occult infection, tumor, or early degenerative FA Matsen, eds: The shoulder, ed 2. Philadelphia, 1998, WB Saunders. disease. When considering a diagnosis of inflammatory disease or infection, routine blood tests such as a complete blood count, 9. McQuade KJ, Dawson J, Smidt GL: Scapulothoracic muscle fatigue associated with erythrocyte sedimentation rate, C-reactive protein, rheumatoid alterations in scapulohumeral rhythm kinematics during maximum resistive shoulder factor, and antinuclear antibodies may be useful. Joint aspiration elevation. J Orthop Sports Phys Ther 28(2):74-80, 1998. 10. Miller TT: Imaging of elbow disorders. Orthop Clin North Am 30(1):21-36, 1999. 11. Morrey BF, Askew LJ, An KN, Chao EY: A biomechanical study of normal functional elbow motion. J Bone Joint Surg 63A:872-877, 1981. 12. Morrey BF, Itoi E, An K: Biomechanics of the shoulder. In CA Rockwood Jr, FA Matsen, eds: The shoulder, ed 2. Philadelphia, 1998, WB Saunders. 13. Neer CS II: Impingement lesions. Clin Orthop Relat Res 173:70-77, 1983. 14. O’Driscoll SW: Classification and evaluation of recurrent instability of the elbow. Clin Orthop Relat Res 370:34-43, 2000. 15. Plate AM, Green SM: Compressive radial neuropathies. Instruct Course Lect 49:295-304, 2000. 16. Pomianowski S, O’Driscoll SW, Neale PG, Park MJ, Morrey BF, An KN: The effect of forearm rotation on laxity and stability of the elbow. Clin Biomech 16:401-407, 2001. 17. Posner MA: Compressive ulnar neuropathies at the elbow. I. Etiology and diagnosis. J Am Acad Orthop Surg 6(5):282-288, 1998. 18. Potter HG. Imaging of posttraumatic and soft tissue dysfunction of the elbow. Clin Orthop Relat Res 370:9-18, 2000. 19. Regan WD, Morrey BF: Physical examination of the elbow. In BF Morrey, ed: The elbow and its disorders. Philadelphia, 2000, WB Saunders. 20. Rehak DC: Pronator syndrome. Clin Sports Med 20(3):531-540, 2001. 21. Rempel DM, Harrison RJ, Barnhart S: Work-related cumulative trauma disorders of the upper extremity. JAMA 267:838-842, 1992. 22. Richards RR, Bigliani LU, Gartsman GM, Iannotti JP, Zuckerman JD: A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg 3:347-352, 1994. 23. Teefey SA, Middleton WD, Yamaguchi K: Shoulder sonography: state of the art. Radiol Clin North Am 37:767-785, 1999. 24. Tennent TD, Beach WR, Meyers JF: A review of the special tests associated with shoulder examination. Part I. The rotator cuff tests. Am J Sports Med 31(1): 154-160, 2003. 25. Tennent TD, Beach WR, Meyers JF: A review of the special tests associated with shoulder examination. Part II. Laxity, instability, and superior labral anterior and posterior (SLAP) lesions. Am J Sports Med 31(2):301-307, 2003. 26. Tillander B, Franzen LE, Karlsson MH, Norlin R: Effect of steroid injections on the rotator cuff: an experimental study in rats. J Shoulder Elbow Surg 8(3):271-274, 1999. 27. Walch G, Boulahia A, Calderone A, Robinson AHN: The “dropping” and “hornblower’s” signs in evaluation of rotator cuff tears. J Bone Joint Surg 80B(4):624, 1998. 28. Zuckerman JD, Kummer FJ, Cuomo F, Simon J, Rosenblum S: The influence of cora- coacromial arch anatomy on rotator cuff tears. J Shoulder Elbow Surg 1:4-12, 1992.

5dC H A P T E R as an effective restraint to external rotation and anterior transla- tion of the humeral head with the arm at the side of the body; Treatment of Shoulder however, it is ineffective in doing so with the arm abducted to Disorders 90 degrees.147 At 90 degrees of abduction, the subscapularis lies above the equator of the humeral head and cannot reinforce the Anthony M. Buoncristiani, Paul H. Marks, and Freddie H. Fu anterior aspect of the shoulder. Disorders of the shoulder girdle are very common and can limit The vascular anatomy of the cuff tendons has been reported participation in vocational, recreational, and professional activi- by many authors. Most have concluded that the supraspinatus ties. Developing an approach to the management of shoulder has a “critical zone” that is prone to calcium deposits and poten- disorders relies on appropriate history taking, physical examina- tial rupture.103 Rathbun and MacNab122 found that filling of the tion, and imaging. This chapter outlines the treatment of most cuff vessels was dependent on the position of the arm at the time common shoulder problems, including rotator cuff pathology; of injection. They documented poor filling of the supraspinatus instability; fracture and dislocations of the sternoclavicular joint, tendon near its attachment to the greater tuberosity and sug- clavicle, acromioclavicular joint, and proximal end of the humerus; gested that tendon failure may be caused by “constant pressure frozen shoulder; and degenerative joint disease. from the head of the humerus which tends to wring out blood supply to the tendon when the arm is held in the resting posi- ROTATOR CUFF DISEASE IN THE SHOULDER tion of adduction and neutral rotation.”122 In an older patient who complains of shoulder pain, the diagnosis The long head of the biceps may be considered a part of the of rotator cuff disease must be considered. This entity is very com- rotator cuff. It attaches to the supraglenoid tubercle of the mon and important. In 1934, Codman’s classic publication32 sum- scapula. This structure is positioned to function as a humeral marized 25 years of observations on the musculotendinous cuff head depressor. It also guides the humeral head as it is ele- and its components. Coleman also discussed ruptures of the vated.141 The concomitant tears that occur in the rotator cuff and supraspinatus tendon and performed the first repair of the cuff in biceps tendon attest to the close functional relationship between 1909. Although there have been recent advances in diagnosis and these two structures. imaging of the rotator cuff, current views and treatments are quite similar to concepts proposed 50 years ago. Neer stated that “impingement of the rotator cuff beneath the coracoacromial arch has been recognized as one of the causes of Anatomy and function chronic disability of the shoulder.” Anatomically, this problem occurs during elevation of the arm anterior to the scapular plane. The components or musculotendinous units of the rotator cuff are He attributed pathologic changes of the rotator cuff to mechan- known to function as dynamic stabilizers for the glenohumeral ical impingement and believed that most rotator cuff tears were joint. Electromyographic and biomechanical studies have demon- due to attritional tears from a narrow supraspinatus outlet.24,106 strated the role of the rotator cuff in providing support of the cap- Additionally, Neer discussed associated alterations on the under- sule and preventing excessive anterior and posterior movement. surface of the anterior third of the acromion, the coracoacromial Studies have suggested that the rotator cuff contributes between ligament, and in time the acromioclavicular joint. He described one third and one half of the power of the shoulder in abduc- three different stages of impingement. Stage I usually occurs in tion and at least 80% of the power in external rotation.30 patients less than 25 years old. Pathology is characterized by edema and hemorrhage. The clinical course is reversible and con- The rotator cuff, which consists of the subscapularis, servative treatment is suggested. Stage II is seen in the 25-year-old supraspinatus, infraspinatus, and teres minor, functions to approx- to 40-year-old age group. Pathology includes fibrosis and ten- imate the humeral head to the glenoid cavity. The supraspinatus dinitis. These patients have activity-related pain, and treatment assists the deltoid in abduction, whereas the subscapularis, infra- may be surgical if there is no response to rehabilitation. Stage III spinatus, and teres minor serve to depress the humeral head dur- disease typically occurs in patients greater than 40 years old. ing elevation of the arm. Depression of the humeral head during Pathology in this group includes acromioclavicular spurs and elevation of the arm helps to avoid impingement. The infra- full-thickness cuff tears. These patients have progressive disabil- spinatus and teres minor function to externally rotate the arm. ity and are often candidates for acromioplasty and repair. These muscle actions may also reduce the strain on the inferior glenohumeral ligament with the arm abducted and essentially Bigliani et al17 reported on a morphologic study in which the rotated.28 In this position, they serve to pull the humeral head variation in shape of the acromion was correlated with tears of the posteriorly. The subscapularis internally rotates the arm. It serves rotator cuff. They described three types of acromion. Type I has a flat profile, type II has a smooth curve, and type III has an angu- lar curve or “hook type” of acromion. The latter type was noted to be present in higher frequency with complete tears of the rotator cuff. Neer108 suggested an important role of the rotator cuff in maintaining a so-called watertight joint space and allowing contin- uation of the normal synovial fluid mechanics that maintain car- tilage nutrition and may prevent secondary osteoarthritis. The scapulothoracic joint must also be considered when rota- tor cuff problems are managed. The scapula sits on the posterior- lateral aspect of the thorax. It is angled approximately 30 degrees anterior to the frontal plane. As a result of this, abduction of the

182 Chapter 5d ● Treatment of shoulder disorders arm relative to the scapula occurs 30 to 40 degrees anterior to the throwing athletes.71 It is hypothesized that in throwing athletes, frontal plane. Abduction of the arm in the scapular plane places weakness and fatigue of the rotator cuff results in overload of the the rotator cuff muscles in their most efficient position and passive restraints. This results in laxity and subluxation of the reduces tension on the joint capsule. glenohumeral joint and leads to secondary impingement. Additionally, the rotator cuff muscles are eccentrically overloaded The scapula is approximated to the thorax by the scapulotho- as they attempt to stabilize the head of the humerus in the gle- racic muscles. These include the upper, middle, and lower noid cavity. Repetitive eccentric overloading of the rotator cuff trapezius, serratus anterior, rhomboideus major and minor, leva- results in inflammation and injury to the rotator cuff tendons. tor scapulae, pectoralis minor, and subclavius. These muscles must function to position and stabilize the scapula during move- Clinical presentation ment of the arm. History Inman et al70 described scapulohumeral rhythm as the coor- dinated motion between the scapula and humerus that occurs Most patients with rotator cuff pathology are over 40 years of age. when the arm is elevated through its full range. During the first Fifty percent of patients recall a traumatic incident that initiated 30 degrees of elevation of the arm, motion primarily occurs at the the symptoms. They usually do not describe a major injury. One glenohumeral joint and the scapula is said to be setting. Elevation can usually elicit a history of recurrent “bursitis” and/or “ten- of the arm beyond this occurs in a 2:1 ratio of glenohumeral to donitis”; these episodes often resolve with rest or other conserva- scapulothoracic motion. The total arc of elevation is a result of tive measures. With time, there is increasing shoulder discomfort. approximately 120 degrees of motion of the glenohumeral joint This is noted with forward elevation and external rotation of the and 60 degrees of motion of the scapulothoracic joint. Motion of arm against resistance. Patients may have complaints of nocturnal the scapulothoracic joint occurs as a result of elevation and rota- discomfort, particularly when sleeping on the affected side. tion at the sternoclavicular and acromioclavicular joints. Patients may describe crepitation with movement. Normal scapulohumeral rhythm is important for normal Physical examination function of the shoulder girdle; it allows for maintenance of the length-tension relationship of the rotator cuff muscles, which The physical findings may be related to the underlying pathol- allows them to function efficiently throughout the full arc of ogy. Crepitation would relate to the lack of smooth surfaces in motion. Additionally, proper movement of the scapula positions the subacromial space. Weakness of flexion, abduction, and the glenoid under the humeral head to enhance glenohumeral external rotation relates to loss of the tendonous attachment to stability. Poor motion and positioning of the scapula have been bone. Upward riding of the humeral head on deltoid contraction linked to impingement and rotator cuff problems. results from a loss of the depressor action of the rotator cuff, and this further exacerbates impingement and cuff degeneration. Classification of injury Partial tears of the rotator cuff may cause pain with motion, Cuff tendon failure can be classified by various criteria. These crepitation, and stiffness. A complete tear may reveal a palpable include partial- or full-thickness tears, acute or chronic injury, defect of the cuff. As previously noted, associated tendonitis of and traumatic or degenerative etiology. The cuff pathology is the biceps may be present, and this should be documented. almost always near the tendon insertion. It nearly always occurs in the supraspinatus component of the rotator cuff, because this The patient should be examined for impingement signs. is the area that is subject to mechanical impingement against the Specifically, this includes full-forward flexion with pain at termi- coracoacromial arch. A full-thickness tear extends from the bur- nal motion, otherwise known as the Neer impingement sign. sal side through to the humeral aspect of the cuff. A partial tear Pain may also be elicited with the Hawkins test, a provocative may involve the bursal or the humeral side of the tendon. Acute test that elicits pain from impingement by bringing the arm into tears occur suddenly and are found in only a relatively small por- forward flexion, adduction, and internal rotation, thus driving tion of patients with rotator cuff pathology. Chronic tears are more the supraspinatus insertion into the coracoacromial arch and cre- common and are usually insidious in onset. It should be noted that ating pain. The acromioclavicular joint can be stressed with the size of the complete tear can also be used to describe the cross-chest adduction. Stability of the biceps tendon should be pathology. A “massive tear” is the term used by Cofield33 to elicited. Bicipital pathology tests include those of Speed and describe a defect more than 5 cm in diameter. Yergason. Speed’s test reproduces pain with resisted forward ele- vation of the humerus against an extended elbow. The pain is The incidence of full-thickness rotator cuff tears has been localized to the bicipital groove area. Yergason’s test reproduces documented in various cadaver studies as being between 5% and pain over the bicipital groove with resisted supination of the 26.5%.111,157 The incidence of cuff pathology has also been forearm with a flexed elbow. Muscle strength testing about the documented in clinical subjects. Age has been found to correlate shoulder is part of the neurologic examination and should be with incidence.102 Moseley102 found that the incidence rose dra- documented. matically with the age of the patient. Traumatic cuff tears have also been found in patients with anterior-inferior dislocations. Differential diagnosis Arthrographically documented tears were seen in 30% in the fourth decade and 60% in the sixth decade.119 When assessing a patient with a suspected tear of the rotator cuff, one should consider other underlying pathologies in the The role of secondary impingement and eccentric overload differential diagnosis. These include cuff tendonitis, bursitis, has been recognized in the pathogenesis of rotator cuff injuries in frozen shoulder, cervical spondylosis, suprascapular neuropathy,

Chapter 5d ● Rotator cuff disease in the shoulder 183 snapping scapula, acromioclavicular or glenohumeral arthritis, must be restored, with particular emphasis on restoration of and glenohumeral instability. external rotation. External rotation is necessary so that the greater tuberosity can clear the acromion as the arm is elevated Methods of treatment overhead. Joint mobilization techniques should be used if gleno- humeral mobility is decreased. Often, the posterior capsule is Despite rotator cuff pathology, not all patients are symptomatic, tight and requires stretching. Stretching exercises can also be so aggressive treatment is not indicated in an asymptomatic used to increase motion. Joint mobilization should be avoided shoulder. In a symptomatic shoulder, the goals of treatment are for patients with hypermobility. For these patients, the focus of elimination of pain, restoration of function, and prevention of treatment should be on the development of dynamic stabiliza- recurrence or progression. tion. This requires strengthening of the rotator cuff and proprio- ceptive exercises to retrain the muscles to dynamically stabilize Nonoperative treatment the glenohumeral joint. Finally, strengthening of the axioscapu- lar muscles (serratus anterior, trapezius) is important to establish Nonoperative modalities of treatment include physical therapy, normal scapulothoracic motion and decrease the role of scapu- rest, elimination of aggravating activities, and administration of lothoracic dyskinesia in impingement biomechanics. antiinflammatory medications and steroid injections. In one study, 44% of the patients with arthrogram-proven rotator cuff Strengthening exercises begin with isometrics with the shoul- tears were shown to respond to nonoperative treatment.143 der positioned in 30 to 45 degrees of abduction in the scapular plane. Active and light progressive resisted exercises are initiated Successful nonoperative management of impingement and as tolerated. These should specifically strengthen the rotator cuff rotator cuff injuries requires an understanding of the anatomy muscles. Several studies have demonstrated maximum elec- and biomechanics of the shoulder girdle and an appreciation of tromyographic activity in the rotator cuff muscles with a variety the underlying etiology. Treatment is based on the patient’s signs of exercises.18,146 The supraspinatus may be strengthened by per- and symptoms at examination. Progression should be based on the forming abduction in the scapular plane with the arm internally response to treatment. General goals for the rehabilitation of an rotated, but caution must be taken to avoid further impingement individual with rotator cuff pathology are listed in the box on with this exercise. Additionally, the supraspinatus may be this page. strengthened by performing prone horizontal abduction with the arm abducted to 100 degrees in the frontal plane and maxi- Patients with acute signs and symptoms complain of constant mally externally rotated. The infraspinatus may be strengthened pain at rest that is referred distally over the deltoid insertion, and by performing prone horizontal abduction with the arm abducted they generally exhibit decreased motion with pain before resist- to 90 degrees in the frontal plane and externally rotated. The teres ance with passive testing. minor may be strengthened by prone external rotation with the arm abducted to 90 degrees. The subscapularis may be strength- During this phase, the focus of treatment is on pain control. ened by performing internal rotation with the arm at the side. This includes the use of relative rest to avoid those activities that Both eccentric and concentric phases of the rotator cuff exercises aggravate the symptoms. Additionally, the patient is encouraged to are emphasized. Adding excessive resistance to these exercises position the arm in abduction in the scapular plane. This reduces should be avoided because it will only result in substitution by pain and prevents “wringing out” of the rotator cuff as described larger muscles of the shoulder complex. These exercises must be earlier. Pain-relieving modalities are used and may include ice, performed precisely without substitution to develop specific mus- moist heat, and transcutaneous electrical nerve stimulation. Gentle cles of the rotator. Internal and external rotation with the arm at mobilization and range-of-motion exercises are performed to the side of the body will not fully develop the rotator cuff. prevent loss of motion and development of a stiff shoulder. Strengthening exercises for the scapular muscles should also be included. Particular emphasis should be placed on strengthening Patients in the subacute phase have intermittent pain that is the middle and lower trapezius as well as the serratus anterior. more localized to the shoulder. The pain may be aggravated by repeated movements. Motion may be limited and resisted testing Successful treatment of rotator cuff injuries is dependent on may be weak and painful. During this period, treatment contin- an understanding of the underlying anatomy and biomechanics, ues to consist of relative rest, and modalities can be used to as well as an appreciation of the underlying etiology. Treatment decrease pain and promote healing. The intensity of exercise can must be appropriate for the patient’s stage of inflammation. be progressed. The focus is on restoration of the normal motion Knowledge of the functional demands placed on the shoulder necessary for function of the individual. Full range of motion is also necessary. Signs of overly aggressive treatment must be recognized and include increased pain greater than 2 hours after Goals of rotator cuff treatment treatment and/or regression of motion or strength. If the patient’s symptoms do not improve after 3 to 6 months, further Control pain investigation with imaging modalities as discussed before is indi- cated. Some would suggest that nonoperative treatment should Restore motion continue, but only about 50% of such patients respond. Improve rotator cuff function Operative treatment Strengthen scapular muscles Samilson and Binder135 outlined the following indications for operative repair: (1) a patient “physiologically” younger than Correct posture Resume function Prevent recurrence

184 Chapter 5d ● Treatment of shoulder disorders 60 years, (2) a clinically or arthrographically demonstrable full- xenograft, or prosthetic material.34 Latissimus dorsi transfer for thickness cuff tear, (3) failure of the patient to improve with the treatment of massive tears of the rotator cuff has been nonoperative management for a period not less than 6 weeks, described by Gerber et al.53,55 In cases with good subscapularis (4) a need to use the involved shoulder in overhead activities in function but irreparable defects in the external rotator tendons, the patient’s vocation or avocation, (5) full passive range of restoration of approximately 80% of normal shoulder function motion, (6) a patient’s willingness to exchange decreased pain and was obtained. In fact, in a cohort of patients with massive rota- increased external rotator strength for some loss of active abduc- tor cuff tears, Harryman et al59 reported patient satisfaction tion, and (7) the ability and willingness of the patient to cooperate. regarding comfort and function despite greater than 50% demonstrating recurrent tears determined by ultrasonography. Currently, anterior acromioplasty with limited detachment of the deltoid appears to be the most direct, least harmful, and Postoperative care most effective procedure for persistent rotator cuff tendonitis. Ellman43 documented an 88% satisfactory result rate in patients Postoperative care after surgery on the rotator cuff is dependent who have chronic impingement treated by arthroscopic on the status of the deltoid, the size of the repair (i.e., small ver- acromioplasty. Simple debridement of partially torn rotator sus massive), the ability to mobilize tissue, and the safe range of cuffs has allowed an 85% rate of return to activity in a group of motion achieved at surgery. Therefore, postoperative care must patients treated by Andrews et al.7 Although acromioplasties are be individualized to the patient and the procedure rather than still routinely performed in conjunction with rotator cuff everyone being treated with a standardized protocol. repairs, recently Matsen and coworkers91 published their results on 96 patients who underwent mini-open rotator cuff repair with- Immediate postoperative care after rotator cuff surgery should out acromioplasty. Significant improvement in self-assessed shoul- protect the healing structures, control pain, and restore range of der comfort and in each of the 12 shoulder functions was observed. motion. For small tears, the arm is generally immobilized at the side for 4 to 6 weeks with a deltoid-splitting technique. Pain- Burkhart26 published results of arthroscopic treatment of mas- relieving modalities can be used to improve comfort. Passive sive rotator cuff tears. He treated 10 patients with painful, mas- range-of-motion exercises are begun immediately postoperatively sive, complete tears involving primarily the supraspinatus with and performed several times per day in the range prescribed by arthroscopic acromioplasty and rotator cuff debridement. All the surgeon. Once sufficient healing has occurred (i.e., at 4 to patients except one had normal preoperative motion and strength. 6 weeks), active assisted and active range-of-motion exercises can These patients maintained adequate mechanics of the gleno- be initiated. Strengthening exercises using isometrics can also be humeral joint during abduction because there is a balance of two initiated at this time. important force couples.120 The first force couple is in the coronal plane and consists of the rotator cuff and deltoid such that the Postoperative management after the repair of massive tears in rotator cuff maintains a fixed fulcrum for rotation of the deltoid which the deltoid was detached includes immobilization for up during abduction. The second force couple acts in the transverse to 6 weeks. Generally, an abduction pillow is used to reduce ten- plane and consists of a balance between the anterior and posterior sion on the postoperative repair. Modalities are used to control portions of the rotator cuff that allows the humeral head to main- pain as necessary. Passive range of motion is performed for the tain centering during rotation of the glenohumeral joint. This first 6 weeks. The safe range of motion achieved at surgery must study showed that normal shoulder function is possible with mas- be communicated by the physician to the therapist. Active sive unrepaired rotator cuff pathology. Similar results were seen assisted and active range-of-motion exercises are delayed for with Motycka et al104 with their cohort of 64 patients with large 6 weeks to ensure adequate tissue healing. Isometric strengthen- rotator cuffs tears followed for a mean period of 5 years. ing exercises are usually delayed until 12 weeks after surgery. As arthroscopic techniques improve, more surgeons are treat- Once sufficient time for healing has passed, the patient is ing rotator cuff pathology arthroscopically. Several articles have gradually progressed through the rehabilitation program. Initial been published demonstrating equal results comparing all arthro- emphasis is on restoring the motion necessary for normal func- scopic versus mini-open rotator cuff repair.25,137,148 However, for tion of the shoulder complex. Attention is directed at reestablish- most cuff tears that come to operative management, an open ing normal scapulohumeral rhythm. Additionally, strengthening approach is still used. The extent of the rotator cuff tear is ascer- exercises focus on developing the rotator cuff and scapular mus- tained at the time of surgery, and the torn edges of the rotator cles. Functional activities are incorporated to allow gradual cuff are identified. The following sequence has been suggested for resumption of function. The patient must be willing to accept closure: (1) resection of the bursal scar, (2) identification of the some limitation in level of function. tear, (3) assessment of tissue mobility, (4) mobilization of the rotator cuff, and (5) planning for closure, either side to side or in In patients who complain of shoulder pain, pathology of most cases to a trough in bone.81 Concomitant acromioplasty is the rotator cuff is important to consider because of the large performed in these patients. Long-term results of this technique spectrum of disease from impingement to complete and massive were reported by Bigliani et al.16 In patients with an average fol- tears of the rotator cuff. Many patients may respond to nonop- low-up of 7 years, 85% had satisfactory results with adequate pain erative therapy, although slightly fewer than 50% may fall into relief and 92% could raise the arm above the horizontal plane. this group. After careful history taking and physical examination, most patients can initiate a course of nonoperative management. Many techniques have been described for massive tears that In those patients who do not respond, imaging of the cuff is the cannot be treated as just outlined. These options include accepting next appropriate step in the algorithm. In patients with simple ten- the defect, moving local tissue into the deficient area, and inserting dinitis or impingement, conservative management is continued. a free graft of local or distant tissue, that is, either an allograft, If symptoms persist, acromioplasty, either open or with endoscopic techniques, can be considered. Patients with complete disruption

Chapter 5d ● Shoulder instability 185 or full-thickness disruption may be candidates for other operative Appreciation of the direction of instability is critical to selec- approaches as outlined earlier. The most direct and simple repair tion of a successful approach to treatment. Traditionally, 95% of technique is often the most appropriate: progression from direct all instability has been observed to be simple anterior instability; tendon repair, to repair of bone, to transposition of local tissue, to however, there has been increasing recognition of significant grafting. Postoperative support should vary according to need. posterior instability in athletes who are loose-jointed individu- Physiotherapy after surgery is a vital part of the treatment protocol. als.8,52 Posterior instability is usually subluxation inasmuch as dis- location occurs only with rarer traumatic episodes.52 Since Neer SHOULDER INSTABILITY and Foster’s article on multidirectional instability (MDI), there has been an increasing awareness of both atraumatic and trau- A rational approach to surgical management of instability should matic capsular laxity occurring in more than one direction. The be based on an understanding of the definition of successful repair main direction of instability is usually anterior, although inferior and an appreciation of the reasons for failure. Successful surgery is instability appears to be the hallmark of this diagnosis.5,37,49,109,112 traditionally defined as elimination of recurrence of instability. Traditional procedures that treat anterior capsular laxity by According to this definition, up to a 97% rate of excellent results Bankart repair or capsular plication do not adequately manage has been reported with a large variety of procedures.* the associated components of inferior and/or posterior instability. In the worst scenario, these procedures can actually lead to insta- Both operative and nonoperative treatment must be based on bility in the opposite direction. an appreciation of the spectrum of glenohumeral instability. A classification system for shoulder instability should include Failure of the operative approach may occur at any point in the following factors: frequency of occurrence, etiology, direction the course of treatment and may be due to either physician or of instability, and degree of instability. One can distinguish patient error or a combination of the two. For a successful out- between traumatic recurrent instability and atraumatic recurrent come, the diagnosis, surgical procedure, and rehabilitation must instability. The former occurs as a result of a single episode of be individualized and appropriate in each case. macrotrauma, is usually unilateral, is less responsive to a rehabil- itation program, and has the Bankart lesion as the most common A correct diagnosis is critical in categorizing the instability and primary pathology. The latter may occur as the result of repeti- recommending the appropriate form of treatment. For example, tive microtrauma (e.g., swimming or throwing), may be bilateral, a misdiagnosis of impingement or failure to recognize a con- is responsive to a therapy program, and has excessive capsular comitant rotator cuff tear in a patient over the age of 50 may laxity as the most common primary lesion. Voluntary instability is lead to failure despite a technically adequate anterior stabiliza- found in a subset of individuals with a traumatic instability. These tion procedure. Additionally, a Bankart procedure that ignores patients can be further subdivided into two groups. Group I the inferior component of capsular laxity in a patient with MDI patients with voluntary instability have an arm position-depend- will fail. ent instability that is usually posterior but may be anterior. These patients usually respond to rehabilitation and do not have an Assuming a correct diagnosis, a variety of technical pitfalls is underlying psychiatric disturbance. If they remain refractory to encountered with each type of stabilization procedure. Appropriate conservative treatment, they may be well managed by surgery. anterior capsular tension must be restored, and procedures that Group II patients have the ability to selectively contract muscles over-tighten the anterior capsule or subscapularis tendon may to create a dislocation. Some of these individuals have an under- result in serious functional limitation of external rotation. In some lying psychiatric disturbance and use their instability as a trick to cases this may lead to osteoarthritis or exacerbation of posterior control their environment.131 These individuals are not candi- instability in patients with unrecognized MDI.63,159 dates for surgical treatment and are better managed by psychi- atric counseling and conservative rehabilitation. Knowledge of the regional anatomy or an inadequate exposure predisposes to an inadequate repair and possible neurovascular There is a spectrum of glenohumeral instability in which injury.125 Assuming the correct diagnosis and correct procedure, subluxation and dislocation represent degrees of injury to the cap- the failure of patient compliance or inappropriate rehabilitation sulolabral structures. Dislocation is defined as complete separation may result in limited range of motion or recurrence of instability. of the articular surfaces, and subluxation represents increased humeral head translation within the glenoid to a degree beyond To avoid complications of treatment, it is critical to be both normal tissue laxity. Because the parameters of normal gleno- sensitive and specific in the initial diagnostic assessment of the humeral translation have not yet been fully defined,136 clinical sub- individual’s shoulder complaints. Both the degree and direction luxation is defined as detectable glenohumeral translation with of any instability must be accurately determined, and any associ- accompanying symptoms. The increased use of arthroscopy has ated fractures, neurovascular injury, or concomitant rotator cuff led to the characterization of an additional group within this spec- pathology must be identified. trum of instability. This group appears to be throwing athletes in whom symptomatic labral tears or attrition develops secondary to Impingement syndrome increased glenohumeral translation without clinical subluxation.4,6,9 Impingement syndrome may occur either as an isolated entity or *References 1, 2, 6, 14, 21, 22, 29, 41, 47, 72, 84-88, 90, 97, 101, 109, 112, 124, 130, in combination with instability.62,156 Hawkins and Hawkins63 139,144. identified several patients whose untreated impingement syndrome was the cause of their ongoing pain after anterior shoulder stabi- lization. This should not be confused with the common finding in patients with anterior instability of pain located posteriorly in combination with clinical findings consistent with impingement

186 Chapter 5d ● Treatment of shoulder disorders syndrome.64,150 This impingement pain is likely a secondary phe- Group I: If after reduction no significant weakness of external nomenon related to repetitive traction and compression of the rotation or abduction is found, immobilization should be rotator cuff during subluxation or to overwork of the rotator cuff continued no longer than 7 to 10 days. A gentle range-of- muscles in an attempt to maintain the humeral head centered in motion program should begin and progressive supervised the glenoid in the setting of capsular insufficiency. Jobe et al72,134 therapy should follow. Failure to move the shoulder early in described this overlap in the literature, and Altchek et al6 observed these patients can result in marked limitation of motion. a 20% incidence of impingement symptoms in individuals with surgically confirmed anterior-inferior MDI. In most cases it is pos- Group II: Patients with persistent pain and external rotation and sible to correctly diagnose impingement syndrome from the his- abduction weakness likely have an associated rotator cuff tear. tory and examination; however, if this evaluation is inconclusive, Early arthrography and electromyography should be performed examination under anesthesia and arthroscopic inspection assist in to confirm this fact and to rule out any associated axillary nerve clarification of the diagnosis. injury. Conservative treatment in this setting usually results in a poor outcome.63 Early repair of the rotator cuff generally yields Anterior shoulder instability in a patient older than 40 years good results, and surgery performed after a delay in diagnosis of age is a unique situation that deserves special consideration if may be fraught with difficulty because the cuff tissues may complications and failure of treatment are to be avoided. The become extensively scarred and difficult to mobilize.62,113 If the association of concomitant anterior shoulder dislocation and patient does have an associated axillary nerve injury, we would rotator cuff tear has been reported by numerous orthopedic sur- still perform an early repair of the cuff, although final function geons.† This concomitant injury may be missed if one is not will likely be determined by return of axillary nerve function. attentive. Moreover, there is an increased risk for adhesive cap- sulitis in this older group of patients if early range of motion is Group III: Recurrent instability in older patients may be due to not begun after reduction of a dislocation. either a rotator cuff tear or excessive capsular laxity.62,77,113 Labral lesions may occur but are less common in this group. The incidence of an associated rotator cuff tear in this group Examination usually reveals those patients with generalized has been reported to be as high as 70% to 90%.62,94,95 Most ligamentous laxity, but an arthrogram is essential to clarify recently, Neviaser et al113 and Hawkins et al62 increased our under- the status of the rotator cuff. It is prudent to know the pathol- standing of this problem. Anterior dislocation in an older individ- ogy before surgery is attempted because most cuff pathology ual may result in disruption of a rotator cuff that has undergone is best treated through an anterior superior approach with an age-related attrition. The anterior capsulolabral structures are acromioplasty, whereas anterior capsulolabral pathology is spared.62,123 McLaughlin92 and subsequently Craig38 termed this managed through a deltopectoral interval approach. It should the posterior mechanism of anterior shoulder instability. be noted that Neviaser et al113 observed a significant sub- scapularis tear in all cases of recurrent instability. In older patients with persistent external rotation and abduc- tion weakness after the reduction of an anterior dislocation, Fracture of the greater tuberosity, the second most common physicians should avoid the trap of assuming an axillary nerve associated fracture after the Hill-Sachs lesion, occurs in about injury as the etiology.38,113 The overall incidence of clinically sig- 10% of all anterior dislocations.92 In most cases this fracture nificant axillary nerve injury in this setting has been reported to reduces anatomically with reduction of the glenohumeral joint be in the range of 9% to 18%.19,126 Neviaser et al113 observed an and recurrence of shoulder instability is actually less than if no incidence of 7.8% for axillary nerve injury in association with fracture were present.92 Displacement of the greater tuberosity rotator cuff tear after anterior dislocation. A suprascapular nerve fragment more than 1 cm may result in residual impingement injury is rare in the setting of anterior dislocation.38 and blocked external rotation. In these cases, surgical reduction and fixation may be necessary. In general, older patients have a lower rate of recurrence of instability after an initial episode of anterior instability.132 This is A glenoid rim fracture may occur with anterior dislocation particularly true if there is an associated fracture of the greater and continued displacement of the anterior glenoid articular sur- tuberosity that reduces the range of motion of the joint and mus- face of greater than 25% to 35% results in recurrent instabil- cle strength.95,126 In older patients with an unrecognized rotator ity.11,80,129 Computed tomography demonstrates this clearly, and cuff tear, pain and weakness appear to be more common prob- surgical reduction and fixation may be necessary if residual lems than recurrent instability.62,113 displacement is greater than 2 mm. In a separate group of older patients, recurrent anterior shoul- The axillary nerve is the most commonly injured neurovascular der instability develops as the result of an excessively redundant structure, with the reported incidence ranging from 5% to 33% in anterior capsule and no rotator cuff tear.77 These individuals typ- first-time dislocators.19,130 Both a motor and sensory examination ically demonstrate the stigmata of generalized ligamentous lax- should be performed before and after any reduction maneuver ity, including thumb to forearm; hyperextension of the elbow, because complete motor paralysis may occur without any detectable knee, and metacarpal joints; a history of easy bruising, hernias, hypoesthesia. Any residual neurologic deficit persisting longer than and scar spreading; and excessive skin laxity. These features 3 to 4 weeks should be evaluated by electromyography.19 Most should be documented during the examination. patients spontaneously recover over a 6-week period inasmuch as most of these injuries are neuropraxic in nature. An approach to treating older individuals (>45 years) after an initial shoulder dislocation is based on classifying such patients The axillary artery is occasionally damaged with anterior into three groups: dislocation because it is relatively fixed as it passes beneath the pectoralis minor and over the subscapularis.39,73,92,126 This is par- †References 32, 65, 93-95, 113, 142. ticularly the case in older individuals, in whom atherosclerosis

Chapter 5d ● Shoulder instability 187 may render the vessels less compliant to displacement. Clinical significant bone loss of the anterior glenoid or posterolateral findings include severe pain, expanding hematoma, and dimin- humeral head may necessitate supplemental bone grafting. In ished peripheral pulses; an arteriogram should be performed older individuals, an arthrogram may also be appropriate to rule urgently in such cases because timely repair is crucial to a suc- out an associated cuff injury. cessful outcome. An anterior surgical approach through the deltopectoral inter- Failure to recognize the voluntary aspect of a patient’s insta- val is recommended. If necessary for exposure, the superior 1 cm bility may result in the failure of any procedure for recurrent of the pectoralis major insertion may be detached. The anterior instability. Rowe et al131 described a typical patient in this group as 1 cm of the conjoined tendon insertion at the level of the cora- an adolescent with an underlying psychiatric problem, without any coid process can be divided. The subscapularis is usually con- prior history of significant trauma, who can voluntarily dislocate tracted and fibrotic along with the capsule and rotator cuff, and his shoulder and who has essentially normal radiographic findings. the axillary nerve may be stretched tightly across the anterior As already noted, group I patients are typically emotionally stable glenohumeral joint. This must be kept in mind during release of individuals with positional instability.52 Group I patients repre- these tight anterior structures. After release of the subscapularis sent a subset of atraumatic voluntary instability, and if they fail to and capsule, it is often necessary to remove granulation tissue respond to conservative management, an operative procedure that within the joint before the humeral head is reduced. After reduc- reduces the excessive capsular laxity is a reasonable alternative. It tion and repair of the capsule, early motion is preferred rather than is crucial to sort out this group from those in group II, who have spica immobilization advocated by some surgeons.60 Management a muscular-control type of voluntary instability that may be used of glenoid bone deficiency and large Hill-Sachs lesions is dis- as a trick to control the environment. These individuals are man- cussed later. aged by psychiatric counseling and rotator cuff strengthening exercises. The spectrum of MDI includes those individuals with In cases in which the dislocation is older than 1 year or when excessive ligamentous laxity (atraumatic type), those with instabil- the Hill-Sachs lesion is larger than 50% of the articular surface, ity resulting from repetitive overhead activities with extremes the humeral head may no longer be viable and a hemiarthro- of motion (microtrauma type), and those with instability after plasty may be the best alternative treatment. In these cases, violent trauma (macrotrauma type).6,140 placement of the prosthesis at an angle greater than the normal retroversion of 30 degrees (50 to 60 degrees) helps prevent the Recognition of MDI is critical because traditional stabilization recurrence of anterior instability. procedures such as the Bankart or Bristow operations fail to ade- quately address the inferior component of instability.‡ Moreover, Although most procedures have a success rate in excess of too tight an anterior repair in this setting may actually aggravate 95% in providing stability to the shoulder, no single surgical the posterior component of MDI.64,159 technique is perfect. In general, procedures that do not address specific pathology should not be used in the primary surgery set- The diagnosis of MDI is based on the history and the classic ting. An individualized approach to each situation is recom- finding of a significant “sulcus sign” in addition to anterior- mended, because a variety of pathologic lesions may be present posterior laxity demonstrated with a load-and-shift maneuver. in different patients. Furthermore, 50% of these individuals usually have stigmata of generalized ligamentous laxity. The optimum technique, as defined by Cofield et al,35 would be one with the following characteristics: low recurrence rate, low Up to 50% to 70% of these individuals respond well to a complication rate, low reoperation rate, low rate of osteoarthritis rehabilitation program aimed at rotator cuff strengthening if it is (uses no hardware), no limitation of motion, anatomic treatment coordinated with activity modification. This is in contrast to of pathology, and no technical difficulty. Because no one proce- young individuals with posttraumatic, unidirectional, anterior dure satisfies all these criteria, we present specific pitfalls and recurrent instability, who often require surgery.27 their management for a variety of common anterior stabilization techniques. Missed unreduced anterior dislocation may occur in elderly patients, individuals with substance abuse, individuals with seizure Examination under anesthesia disorders, and unconscious polytraumatic patients.60,133 Unlike and diagnostic arthroscopy missed posterior dislocations that go unrecognized because of a failure to perform an adequate radiograph, missed anterior dislo- It is essential to confirm both the direction and the degree of cations are usually due to a failure to perform an initial or fol- instability by examination under anesthesia before any surgical low-up radiograph.60 The chronicity of the dislocation must be procedure. This aids in the decision of which operative approach established. If an anterior dislocation is less than 6 weeks old and and procedure to use. One should perform a drawer test on the no concomitant osteoporosis or history of steroid use is present, shoulder to assess the amount of anterior, posterior, and inferior an attempt at mild gentle closed reduction may be made under translation of the humeral head in the glenoid. Anterior and pos- general anesthesia.60 In cases with chronic unreduced disloca- terior translation is assessed with the shoulder at 90 degrees’ abduc- tions older than 6 weeks, open reduction and stabilization are tion and neutral rotation and is graded on a scale of +1 to +3 recommended. In these cases, an axillary radiograph confirms (+1 is movement of the humeral head to the rim but not over it, the diagnosis; however, computed tomography gives valuable +2 represents humeral head dislocation over the glenoid rim information about the status of the humeral head and glenoid. with spontaneous reduction when pressure is released, and +3 It is helpful to have this information before surgery because is frank dislocation of the humeral head that does not reduce spontaneously).6 One should not be surprised to find increased ‡References 6, 49, 54, 90, 109, 112, 121, 126, 127, 140.

188 Chapter 5d ● Treatment of shoulder disorders posterior translation along with anterior translation when a applying progressive external rotation. An elevator is placed infe- patient with suspected anterior instability is examined because riorly and used to remove any muscle from the capsule before its injury to the ligaments on both sides of the joint may occur with division. If the axillary nerve cannot be palpated and its exact an anterior dislocation.115,136 location is not precisely known, it should be visualized before division of the inferior capsule. Inferior instability is assessed by the presence of a “sulcus sign.” This test is performed with downward traction on the A T-plasty procedure can be performed to manage capsular adducted arm, and the degree of acromiohumeral interval separa- laxity and concomitant labral detachment simultaneously.6 The tion is noted.150 The “sulcus sign” is graded on a scale of +1 to +3 basic goal of the T-plasty is to restore proper tension in the infe- (+1 is 0 to 1 cm, +2 is 1 to 2 cm, +3 is greater than 2 cm).6 rior glenohumeral ligament by advancing this structure superi- Arthroscopic inspection may occasionally be useful in these orly and medially. At completion of the capsular repair, external patients, although office examination, history, and an examina- rotation with the arm at the side should be in the range of 35 to tion under anesthesia usually confirm the diagnosis. Most labral 45 degrees without undue tension on the repair. lesions below the equator of the glenoid are associated with a deficient inferior glenohumeral labrum. The Bristow procedure and its modifications basically involve fixation of the coracoid process and attached conjoined tendon Surgical procedures for instability to the scapular neck through a split in the subscapularis tendon.§ The procedure theoretically functions by provision of an ante- The classic Bankart procedure13,118 and its modifications72,130,144 rior bone block, formation of a dynamic musculotendinous anatomically repair a detached glenoid labrum together with the sling, and partial tenodesis of the inferior third of the subscapu- inferior and middle glenohumeral ligaments. Several variations laris tendon. It does not directly address pathologic lesions such in handling of the subscapularis deserve mention. Thomas and as labral detachment or capsular laxity. Matsen144 described a technique first proposed by Ellison. The subscapularis and capsule are both divided laterally, with medial Although the Bristow procedure has a success rate compara- retraction allowing repair of the Bankart lesion with the joint in ble with that of other procedures, it is generally accepted to be a an inside-out fashion. This approach is useful in revision cases in poor alternative for stabilization in athletes involved in overhead which extensive scarring is found medially at the glenoid. sports, because it may limit external rotation.14,66,85,86 The ortho- pedic literature has documented a high incidence of complica- Jobe and Glousman72 recommended longitudinal division of tions with this procedure.10,12,46,159 the subscapularis muscle with preservation of its lateral insertion on the lesser tuberosity. This approach is designed to minimize The major risk with the Bristow procedure is injury to the scarring and shortening of the muscle in a throwing athlete. musculocutaneous nerve.12,15,48,125,159 This complication is usually Several potential problems with this approach include limited due to inadequate knowledge of variations in regional anatomy or inferior exposure in cases in which a capsular shift might be poor surgical technique.125 Significant variations in anatomy of necessary and the potential for injury to the axillary nerve the conjoined tendon and musculocutaneous nerve may be and brachial plexus if longitudinal splitting is carried too far encountered.48,125 The musculocutaneous nerve, in most cases, medially. enters the coracobrachialis muscle at a distance of 5 or more cm distal to the coracoid process; however, in 5% of cases it may To repair the Bankart lesion once the sutures are well placed also be as close as 2.5 cm from the tip of the coracoid.12,48,125 through the bony anterior glenoid rim, the lateral capsule is If the nerve is observed to enter the muscle at 2.5 cm or closer repaired to the rim. A potential error here is to not address any to the coracoid process, the Bristow procedure should not be concomitant capsular laxity. The standard Bankart procedure performed. Finally, staple fixation may impinge or rupture the handles capsular laxity by placing the sutures more laterally biceps tendon with improper placement. through the lateral capsular flap. The T-plasty repair pulls the inferior portion of the capsule superiorly before placement of The Putti-Platt procedure treats anterior instability by shorten- the sutures through the capsule. ing the subscapularis in a “vest-over-pants” technique to limit external rotation.22,68,84,116 The subscapularis is detached 2.5 mm The inferior capsular shift procedure as originally described by medial to its insertion, and the capsule and subscapularis are then Neer and Foster112 is designed to treat excessive capsular laxity sutured to the glenoid rim with the arm in internal rotation. The occurring with MDI. It has been used successfully and involves main complication of this procedure is loss of function from detachment of the capsule laterally along its humeral attachment excessive limitation of external rotation, and in the extreme case with a superior-lateral shift of the inferior flap and then an infe- this may result in secondary glenohumeral arthritis caused by rior-lateral shift of the superior flap.40,49 Repair of an associated excessive constraining forces on the articular surfaces.61 Instability Bankart lesion is performed first, and failure to address this lesion may also result if the patient has unrecognized MDI.63 has been associated with failure of the procedure.87 Inferior detachment of the capsule laterally along the humeral neck prob- In the duToit capsulorrhaphy procedure, a staple is used to ably involves less risk to the axillary nerve than does a medial effect a Bankart-type repair, and complications stem from prob- paraglenoid capsulotomy incision; however, there is still signifi- lems with staple fixation and placement.20,42,139 Injury to the cant risk with inferior dissection, and Neer109 observed three cases articular surface and loosening of the staple have been of axillary nerve neuropraxia early in his experience. To avoid this reported.160 Metal devices are mentioned here for their historical potential complication, the inferior flap should be developed by role in the development of arthroscopic Bankart repairs. placing stay sutures in the capsule and pulling superiorly while §References 2, 3, 10, 14, 21, 29, 30, 41, 47, 57, 66, 67, 69, 82, 85, 86, 89, 96, 114, 138, 145.

Chapter 5d ● Fractures and dislocations about the shoulder 189 The enthusiasm for arthroscopic stabilization of anterior proximal end of the humerus, and scapula. An associated neu- shoulder instability is based on the assumption that limited rovascular injury may or may not be present. disruption of the anterior soft tissues results in a better func- tional outcome. This is particularly relevant to young throwing Sternoclavicular joint athletes who require full external rotation and power. Although short-term studies with 2- to 3-year follow-up are encouraging, Most often, sternoclavicular dislocations do not cause any signifi- long-term data supporting this assumption are not available.44,76 cant functional disability.24 An anterior dislocation is usually However, three recent meta-analyses comparing arthroscopic ver- asymptomatic and does not require any treatment. Posttraumatic sus open repair for traumatic anterior shoulder instability both ankylosis of the sternoclavicular joint can cause pain and disabil- concluded that open repair has a more favorable outcome with ity. Compression of the mediastinal structures can occur with pos- respect to recurrence and return to activity.36,50,98 Because arthro- terior dislocations of the sternoclavicular joint. In general, anterior scopic management of instability has been in evolution over the injuries can be treated conservatively and posterior injuries may recent years, the conclusions drawn from the meta-analyses may require some intervention. Surgical management of chronic stern- be biased toward success of open repair. oclavicular dislocations may include soft tissue reconstruction, arthrodesis, resection of the medial aspect of the clavicle, and The technique, which was originally popularized by Johnson,74 resection combined with costoclavicular ligament reconstruction. uses a dual-pronged staple and attempts to reproduce the duToit capsular staple-Bankart repair arthroscopically.4,42,150 Since then, Clavicle modified techniques have included the use of a removable rivet,154 modified staple capsulorrhaphy,56 cannulated screw and ligament Clavicular fractures account for greater than 60% of shoulder washers,158 and suture Bankart repair.4,31,99,100 girdle fractures. The middle third of the clavicle is involved in 82% and the distal third in 15%.128 Nonunion of the clavicle is The ideal patient is an individual with posttraumatic, recur- relatively uncommon and reported in 1.8% of those patients rent, anterior, unidirectional instability with labral detachment treated nonoperatively.128 If a nonunion does occur, most often below the level of the equator of the glenoid. Patients with MDI it is minimally symptomatic. One study has determined that are not candidates for this procedure. Routine examination of atrophic nonunions are less likely to become symptomatic than patients under anesthesia is performed before the procedure. are hypertrophic nonunions.155 In a study by Johnson and Individuals with a significant sulcus sign that does not lessen Collins,73 26 clavicular nonunions treated nonoperatively with external rotation and adduction are treated with a rotator resulted in 23 excellent results, 2 good results, and 1 poor result. interval closure. Rowe128 noted spontaneous uniting of apparent nonunions as long as 5 months from the time of injury. Only patients with sig- One can use a suture technique in which absorbable sutures are nificantly symptomatic nonunions and malunions should be placed through the inferior glenohumeral ligament and a Bankart offered reconstructive surgery. repair is achieved through transscapular drill holes.4,31,99,100 Drill holes are placed above the equator on the anterior scapular neck Malunion of the middle third of the clavicle, if symptomatic, to allow restoration of tension in the inferior glenohumeral liga- can be managed with osteotomy and bone grafting. This is sup- ment as it is pulled superiorly and medially with the repair. More plemented with internal fixation. Nonunions can be managed by recently, the use of a biodegradable cannulated tack to avoid excision of the pseudoarthrosis, reduction, bone grafting, and problems associated with hardware or drilling across the scapula internal fixation with promising results.75,110 Distal clavicular has been discussed.149 nonunions, which can result after type II distal clavicle fractures, have been treated by excision of the distal fragment and/or open No matter what form of fixation is used, it is essential to ade- reduction and internal fixation. The results of excision cannot be quately prepare the anterior scapular neck to ensure a bleeding recommended.73 Neer107 documented some success with bony bed for the repair. When a motorized burr is used, care transacromial wire fixation. The fixation is removed after union should be taken not to slip over the glenoid rim and injure the has occurred. However, cases of migratory hardware have made articular surface. Injury to the suprascapular nerve is a theoreti- pin or wire fixation less appealing. cal risk with pin placement through the scapula. Excessive lateral penetration of the pins should be avoided.100 Acromioclavicular joint In conclusion, many pitfalls and complications are poten- tially encountered in surgery for shoulder instability. The shoul- der surgeon must have an organized approach to diagnosis and treatment. If surgery is contemplated, the procedure must be tailored to the individual patient and must deal with the under- lying pathology. FRACTURES AND DISLOCATIONS ABOUT Of shoulder girdle dislocations, 9% involve the acromioclavicu- THE SHOULDER lar joint. Fifty percent are complete grade III or higher disloca- tions with disruption of the conoid and trapezoid components Fractures and dislocations about the shoulder are very common of the coracoclavicular ligaments.128 injuries. These injuries are best classified by anatomic location for the purpose of discussion. Shoulder girdle injuries are located Most acute acromioclavicular injuries can be treated non- at the sternoclavicular joint, clavicle, acromioclavicular joint, operatively: application of ice over the first 24 hours, possibly a sling for comfort, and resumption of activity at approximately 1 week if tolerated. Posterior displacement of the clavicle is

190 Chapter 5d ● Treatment of shoulder disorders uncommon and may require surgery to reduce the clavicle. fracture comminution and displacement, but conversion to hemi- It may be wedged into the angle between the acromion and the arthroplasty is always a possibility after attempted fracture fixation. spine of the scapula. One may attempt a closed reduction by displacing the shoulder posteriorly to widen the distance Two-part lesser tuberosity fractures are often associated with between the acromion and sternum. posterior glenohumeral dislocation. Smaller fragments can be treated nonoperatively: Larger fragments may require open reduc- Treatment of injuries that involve complete separation of the tion and internal fixation. Two-part greater tuberosity fractures may acromion and clavicle is controversial. Some have attempted closed include a tear of the rotator cuff. This requires open reduction and reduction with pressure by tape or a splint, but significant problems internal fixation with either a tension band wire or screw and repair with the skin have been noted when these techniques are used. of the rotator cuff tear. Two-part fractures of the anatomic neck are Surgery for acute grade III lesions has included many techniques105: uncommon and carry a significant risk of osteonecrosis. Flatow et direct acromioclavicular joint stabilization with ligament repair; al48 published a series of 12 two-part greater tuberosity fractures clavicle stabilization by attachment to the coracoid, as with a that were treated surgically by open reduction and internal fixation Bosworth screw, wire, Dacron tape,58 silk sutures, or absorbable with a heavy nonabsorbable suture and careful repair of the rotator suture; and resection of the outer end of the clavicle and coracoclav- cuff. All fractures healed, and early range of motion resulted in icular ligament stabilization with the coracoacromial ligament.151 good or excellent results in all patients. Most patients with chronic acromioclavicular subluxations or Two-part surgical neck fractures can be either impacted or dislocations are asymptomatic or minimally symptomatic and completely displaced and unstable. Options for treatment respond well to nonoperative management. Occasionally, acromio- include closed reduction, with or without percutaneous pinning, clavicular subluxations become symptomatic.105 Degenerative joint or open reduction and internal fixation. Kowalkowski and disease or osteolysis of the distal end of the clavicle may develop. Wallace78 published a series of 22 displaced fractures treated with These problems can be assessed with an acromioclavicular view on closed percutaneous Kirshner wire stabilization of the surgical plain radiographs and by injection with local anesthetic to confirm neck. Significant problems in obtaining adequate reduction and the diagnosis with pain relief. migration of the smooth pins were encountered. Unsatisfactory results were more common in the older age group (greater than Proximal humerus fracture dislocations 50 years old). The classification of proximal humeral fractures is based on the In three-part fractures, closed reduction is often difficult to absence or displacement of each of four major segments: maintain, and therefore open reduction is required. Tension- the humeral head, the greater and lesser tuberosities, and the band wiring can often be used because it incorporates the rota- humeral shaft. The Neer classification is most commonly used tor cuff in the repair. If the fracture is severely comminuted or and considers the segment displaced if there is greater than the bone osteoporotic, a hemiarthroplasty can be considered, 45 degrees of angulation or 1 cm of displacement. It should be especially in elderly patients. noted that all patients with a suspected fracture of the proximal end of the humerus require a shoulder trauma series of radi- In young patients with a four-part proximal humerus fracture, ographs. This includes anteroposterior, lateral, and axillary views. an attempt at open reduction and internal fixation is considered The treating physician must exclude concomitant dislocation of despite the high risk of osteonecrosis. If reconstruction is not the humeral head. A complete vascular and neurologic examina- possible or the patient is elderly and has poor bone stock, a tion must be performed and documented. hemiarthroplasty is preferred. Treatment considerations include the patient’s age, functional As discussed earlier, it is important to eliminate the presence demands, dominance, expectations, anticipated compliance, of concomitant dislocation of the humeral head. Isolated disloca- degree of segment displacement, and bone quality. Most of these tions without fracture can be seen. Many posterior dislocations of fractures can be managed with protective immobilization and the humeral head are missed and recur chronically. These patients early range of motion. This is, of course, based on the aforemen- most often complain of decreased range of motion. They may or tioned factors and includes fracture stability. In a prospective ran- may not complain of pain. Articular impression fractures can domized study of proximal humerus fractures (minimally often best be imaged with computed tomography. In general, displaced), Kristiansen et al79 compared 1 and 3 weeks of immobi- closed reduction can be considered if the injury is less than 6 lization before starting physical therapy. Shorter immobilization weeks old; after 6 weeks, open reduction is required. Treatment resulted in better functional results during the first 3 months. After of the articular impression defect is based on the percentage of 6 months, the results in both groups were essentially the same. head involvement. If the defect is less than 20%, it is generally stable after a period of immobilization. If the defect is between Fractures that are more significantly displaced require reduc- 20% and 40%, a transfer procedure into the defect may be tion. This can be accomplished by closed means or with open required, as well as possibly a subscapularis transfer for posterior reduction and internal fixation. Occasionally, prosthetic replace- dislocations or infraspinatus transfer for anterior dislocations. ment is preferred. Available internal fixation includes tension band A hemiarthroplasty may be used if the defect is greater than 40% wires, screws, percutaneous pins, plates and screws, and of the head or if significant degenerative changes are present. intramedullary nailing. There is a trend toward open reduction and internal fixation as newer types of locking plates become more FROZEN SHOULDER commonly implemented.45 This restores anatomy and provides fracture stability. The risk of avascular necrosis increases with Frozen shoulder—also termed adhesive capsulitis—has many under- lying causes. It can be seen in association with other shoulder

Chapter 5d ● References 191 pathologies, for example, posttraumatic, postsurgical, and excellent pain relief with total-shoulder arthroplasty.51,152 rotator cuff pathology. It is also associated with other disease Reverse-type prostheses are reserved for the elderly person with entities, including insulin-dependent diabetes mellitus, parkin- severely debilitating cuff tear arthropathy or loss of the cora- sonism, cardiovascular disease, and thyroid disease. coacromial arch. However, early reports are fraught with a high complication rate, and its implementation is still being Most patients have an insidious onset of pain and stiffness. defined.83 Most patients demonstrate a gradual decrease in pain and return of motion over time. There may be improvement for up to CONCLUSION 24 months. Treatment consists of gentle physical therapy, antiin- flammatory medication, and occasional use of cortisone injec- In attempting to treat the myriad of shoulder problems, the tions intraarticularly and subacromially. If the patient does not orthopedist must first make an accurate diagnosis. The goals of respond after an extended trial of therapy, consideration may be treatment include controlling symptoms, improving function, given to manipulation under anesthesia. More recently, arthro- and preventing recurrence, if possible. A systematic approach to scopic release and debridement have been proposed.153 Open management includes appropriate conservative modalities and surgical release is rarely indicated and may in fact worsen the surgical intervention, if necessary. Future concerns must address problem. Ozaki et al,117 however, reported on 17 patients treated cost-effectiveness, standards of care, and outcome research. surgically for recalcitrant adhesive capsulitis. 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Philadelphia, 1984, JB Lippincott, arthroscopic repair. Arthroscopy 4:25-30, 1988. pp. 722-860. 155. Wilkins RM, Johnston RM: Ununited fractures of the clavicle. J Bone Joint Surg 127. Rockwood CA Jr: Subluxation of the shoulder: the classification, diagnosis and 65A:773-778, 1983. treatment. Orthrop Trans 4:306, 1979. 156. Willis JB, Meyn MA Jr, Miller EH: Infraspinatus transfer for recurrent anterior dislocation of the shoulder. Presented at the annual meeting of the American Academy of Orthopaedic Surgeons, Las Vegas, February 27, 1981. 157. Wilson CL, Duff GL: Pathologic study of degeneration and rupture of the supraspinatus tendon. Arch Surg 47:121-135, 1943. 158. Wolf EM: Arthroscopic anterior shoulder capsulorrhaphy. Techn Orthop 3:67-73, 1988. 159. Young C, Rockwood CA: Complications of failed Bristow procedure and their man- agement. J Bone Joint Surg 73A:969-981, 1991. 160. Zuckerman JD, Matsen FA: Complications about the glenohumeral joint related to the use of screws and staples. J Bone Joint Surg 66A:175-180, 1984.

5eC H A P T E R EXPOSURE-RESPONSE RELATIONSHIP Workplace Adaptation It is necessary to understand in general and specific terms the rela- for Shoulder Disorders tionship between work factors and conditions that affect fatigue and risk of musculoskeletal disorders (MSDs). This relationship is Thomas J. Armstrong referred to as the exposure-response relationship.4,34,35 Figure 5e.2 shows a hypothetical exposure-response relationship with expo- This chapter is concerned with workplace adaptations for sure on the horizontal axis and response on the vertical axis. preventing work disability due to shoulder, neck, and elbow A number of metrics have been proposed and used for describ- impairments. Disability occurs when work demands exceed ing exposure; some of these are described later in this section. worker capacities (Fig. 5e.1).3,9 Development of workplace adap- Response is typically expressed as the prevalence of symptoms tations requires information about both worker and job demands, or conditions at a given time or as an incidence rate of cases which can then be compared to determine whether new or addi- over time. tional adaptations are required. Although population work capac- ity data can often be determined from published data and Exposure-response relationships typically exhibit a sigmoid models, individual data must be obtained from a qualified health relationship as exposure increases from low to high. The preva- care provider. The health care provider plays an important role lence and incidence of MSDs at low exposures are referred to as also in determining how successful intervention has been and the background level and may be due to personal or other non- whether additional job modifications are required. Development work factors. The prevalence and incidence may also vary from of workplace adaptations requires the affected worker, the health one sign, symptom, condition, and measurement method to care provider, and the employer to work closely together. another. Figure 5e.2 illustrates two examples: curve a shows a low background level and a high sensitivity to work factors and curve Although the concept of disability is straightforward, its b shows a high background level and a low sensitivity to work determination of disability and the development of adaptations factors. are more complex due to the multiple physical, behavioral, and social variables involved. It is possible unwittingly to declare a In the future, we will have sufficient data to specify job designs worker disabled who is not or to declare one able who is not. for given populations that will produce an acceptable level of It may be found, for example, that a worker is disabled because risk. Until then, the exposure-response relationship still provides of a shoulder impairment that restricts his or her reach capacity, important insights for job designers. but that worker might have learned to adapt the workplace by rearranging equipment or standing up to reach distant objects. Exposure-response relationships are based on a series of bio- Similarly, it may be found that a worker is able to reach all the mechanical and physiologic mechanisms.4,34,35 Work activity necessary work objects but is disabled by inability to do the job entails exertion of the body to overcome the weight, resistance, for 8, 10, or 12 hours per day. and inertia of work objects. These forces produce moments about joints that must be counteracted by muscles. The position of the body and the external forces are exposure variables and the moment about the shoulder is a response variable. At a second level, the joint moments can be regarded an exposure variable, whereas the muscle force acts as a response variable. At a third level, muscle forces can be regarded as exposure variables and perceived exertion, discomfort, and fatigue as short-term Disability Modify job Yes Treat worker bResponse Determine job Demands Evaluate a demands > worker Exposure capacities Figure 5e.2 General exposure-response relationship shows an No increasing prevalence or incidence of pain, fatigue, or other Successful adaptation musculoskeletal disorders with increasing frequency and duration of force and posture. Curve a illustrates a low background level and a Figure 5e.1 Basic process for accommodation of work populations or high sensitivity to a given factor and curve b illustrates a high individual workers. background level and low sensitivity to a given factor.

196 Chapter 5e ● Workplace adaptation for shoulder disorders response variables. Chronic tissue injuries and corresponding Law, when a worker reaches for an object, the muscles in the symptoms can be regarded as long-term responses. These biome- shoulder and elbow must produce sufficient moment forces of chanics and physiology relationships are supported by experi- gravity on the arm, forearm, and hand (Fig. 5e.3). A work object mental, psychophysical, and epidemiologic studies.4,34,35 in the hand requires additional muscle force. The load moment on the shoulder, Ms, can be calculated based on the size of the Biomechanics body parts and their weight13,36: An important example of the exposure-response relationship is Ms = cosθ1x1w1 + (cosθ1l1 + cosθ2x2)w2 + found in the shoulder, the examination of which provides useful (cosθ1l1 + cosθ2l2 + cosθ3x3)(w3 + wobject) tools for developing workplace adaptations. By Newton’s Third where l1, l2, l3 are lengths of the arm, forearm, and hand; θ1, θ2, θ3 are angles of the arm, forearm, and hand with respect to Mtot W1 W1 W3 X1 X2 X3 Wobject A I1 I2 I3 q3 q1 q2 B Figure 5e.3 (A) The moment produced about the shoulder is equal to the sum of the moments produced by the arm, forearm, and hand. In addition, the weight of a work object such as a part or tool contributes to the shoulder moment. (B) The angles of the arm, forearm, and hand with respect to the horizontal are shown.

Chapter 5e ● Exposure-response relationship 197 Table 5e.1a Average body link sizes as fractions of Table 5e.1c Body segment weights as percentages total stature16 of total body mass15,29 Link Fraction Link Relative body mass Stature 1.000 Head 6.9% Floor-ankle 0.039 Arm 2.7% Floor-knee 0.285 Forearm 1.6% Floor-hip 0.530 Hand 0.6% Floor-shoulder 0.818 Floor-elbow 0.630 higher for a worker with greater body weight. The biomechanical Floor-wrist 0.485 analysis provides both a qualitative and quantitative rationale for Floor-hand 0.377 job design. Floor-buttocks 0.480 Floor-eye 0.936 Important limitations Center-shoulder 0.129 Shoulder-elbow 0.188 Deliberately simplified for demonstration purposes, this analysis Elbow-wrist 0.145 of shoulder stress generally underestimates the actual loads. Wrist-hand 0.108 Increased loads result from inertial forces associated with acceler- ation and deceleration of the body and work object. Additional the horizontal; x1, x2, x3 are the moment arms between the prox- loads may result also from antagonistic muscle forces. Although imal joint and the center of gravity of the arm, forearm, hand, some antagonistic muscle contractions are inevitable, others may and work object; and w1, wf2, w3, wobject correspond to the weights result from psychologic stresses,7 the contributions of which, of the arm, forearm, hand, and work object. although real, are difficult to quantify and beyond the scope of this discussion. The moment arms can be measured for a given individual or estimated from height of a given population percentile using Other biomechanical considerations the relative link lengths shown in Table 5e.1a16 and the link center of gravity locations shown in Table 5e.1b.15,29 Weights of In addition to the effect on muscle workload, increasing shoul- each segment can be estimated for a given individual or popula- der angles produce pressure on internal and surrounding soft tion percentile weight using the relative segment weight data tissues.22 In fact, although the required muscle loads actually shown in Table 5e.1c. Height and weight data for the U.S. adult decrease as the arm torso arm angle exceeds 90 degrees, pressure population are shown in Table 5e.2. on soft tissues continues to increase. Epidemiologic studies show that elevated elbow postures are associated with elevated incidences The calculated shoulder and elbow moments for persons of chronic shoulder pain and impairment.6 with average female and male stature and weight performing a horizontal reach at elbow height and at shoulder height are shown Other body parts in Figure 5e.4. Figure 5e.4, b, d, f, and h, shows how the moment about the shoulder due to the weight of the arm, forearm, and Similar analyses can be performed for other parts of the body, hand increases with the horizontal reach distance. Added to the such as the neck.23 Bending the neck or torso forward to reach weight of the arm, forearm, and hand, the moment of the weight or see work objects such as documents, controls, or equipment of a held object such as a tool or part would equal the distance produces load moments on the neck that must be counteracted between the shoulder and hand times the weight. Holding a 10 N by internal muscle forces. Extreme rotation of the forearms in (2 pound) tool in the hand at a distance of 0.6 m, for example, combination with forceful exertions of the hands produces stress would add 6 Nm to the 10 Nm of the arm and forearm. on the attachments of the finger flexor and extensor muscles. As a general rule, jobs should be designed so that workers do not have This simple biomechanical analysis can be applied to many to perform sustained or repeated exertions at or near range of motion work tasks. Figure 5e.4, for example, shows a 7-Nm shoulder load limits. Ideally, the elbows should be near the sides of the body, in the shoulder of an average female holding her hands over a the forearms should not be rotated to one extreme or the other, keyboard at a distance of 0.5 m, with the moment proportionally and the head should be held upright. At the other extreme, the work pace should enable workers to periodically stretch and Table 5e.1b Body segment distance from proximal change positions. Even the best posture eventually becomes joint center of gravity15 uncomfortable if it is maintained too long. Link Center of gravity Localized fatigue Arm 43.6% Acceptable work design standards for preventing MSDs that Forearm 43.0% may afflict the elbow, neck, and shoulder have not been estab- Hand 50.6% lished, but recommendations may be made for preventing local- ized fatigue. An important problem in its own right, localized

198 Chapter 5e ● Workplace adaptation for shoulder disorders Table 5e.2 Statures (m) and body masses (kg*) for males and females ages 18 and over from the National Center for Health Statistics11 Female Male Average 5% 50% 95% Average 5% 50% 95% Stature 1.618 1.504 1.618 1.73 1.755 1.636 1.755 1.880 Weight 69.2 48.0 65.6 102.5 82.1 59.7 80.0 110.8 *1 N = kg × 9.8 m/s2. fatigue may be a harbinger or precursor of more serious MSDs.34,35 and places the parts on a moving tray at a distance of 0.32 m. According to the above exposure-response relationship, localized Because the trays are moving, the worker cannot rest her fore- fatigue responses include concentrations of metabolic substrates, arms while waiting for them to come into position. The shoulder metabolites, and ions. These changes may result in altered moments due to the weight of the body and load are calculated electromyograms, reduced motor control, reduced strength, and, in Table 5e.3 and are plotted in Figure 5e.6B. (Loads between perhaps most importantly, pain. Exposures are expressed as successive positions are approximated as straight lines.) It can be percentages of maximum voluntary contraction (% MVC), exer- seen that the moments increase due to the weight of the arms tion frequency, and duty cycle. The % MVCs are computed during the reach. The moment then increases as the part is lifted as the ratio of the required muscle force to that possible for a and then decreases as it is moved into position to wait for the given task, individual, or population or as the ratio of job demands tray to come into position. Finally, the load force decreases to to worker capacities, as shown in Figure 5e.1. Recommended zero as the load is released, but the shoulders must continue to acceptable exposure limits for continuous work previously ranged support the weight of the body. The average total shoulder from 0 to 15% MVC; those for intermittent work range from moment can be calculated as a time-weighted average: 17% to 21% MVC. Bystrom and Fransson-Hall10 recommended an upper limit of 10% MVC for continuous static work and 17% Ms = (∑ tiMi ) MVC for intermittent work. The above biomechanical analysis ∑ ti of the shoulder loads during reaching and lifting can be used to estimate relative muscle workload for a given task, but first it is where Ms is the average shoulder moment, ti is the duration of necessary to consider worker capacity. the ith work element, and Mi is the average total moment produced during the ith element. Worker capacity For this sample task the average moment is calculated as Acceptable workloads vary from group to group and person to person, and design commonly accommodates the general popu- = [0.67 × (4.5 + 9.8)/2 + 0.13 × 9.8 + 0.79 lation or a specific individual. In the former case, work capacity × (16.05 + 7.71)/2 + 2.00 × 7.71 + 0.36 × 7.71 + 0.07 data are typically taken as a lower percentile of the general pop- × (7.71 + 4.5)/2]/4.0 = 8.4 Nm ulation. It is all too common to design for a 5th percentile, a practice that seems to be reinforced by reference books showing This analysis provides important insights into the factors that the 5th percentile, average, and 90th percentile population data. should be considered in evaluating and designing work stations. It The problem is that 5 people out of 100 may be disqualified or is important to know the locations of controls and those where experience significant difficulty or injury doing the job. materials, parts, and tools are stored and used as well as the forces required to obtain, hold, and use work objects. The list of work Design for an individual requires a function evaluation that elements and their durations33 are likewise all significant factors specifies strength limits for that person. The designer should work affecting the load on the shoulder and other parts of the body. closely with the evaluator during and after design implementa- tion to make sure that the job can be performed without risk of As described earlier, loads on the body are frequently normal- injury or reinjury. For discussion purposes, data from Winters ized as a fraction of maximum strength or percent of maximum and Kleweno,40 shown in Figure 5e.5, indicate that female voluntary contraction, % MVC, which is used commonly as a strength is about half that of male strength and that male metric of physical workload and predictor of localized fatigue. strength is sensitive to shoulder posture. The average female Calculation of relative workload requires information about strength of approximately 30 Nm is significantly less for an both the absolute load and the corresponding work strength. elderly or injured worker. Reaching results not only in increased Strength varies among workers, joints and their relative positions, load moments on the shoulder (Fig. 5e.4) but also in decreasing hands, ages, and occupational groups and may be affected by strength (Fig. 5e.5). Vertical reaching also reduces strength. fatigue, injuries, and diseases. The analyst may select a value from the literature that corresponds to the population of interest Figure 5e.6 shows a job in which a female of average stature, or use data provided by a functional evaluation of a specific proportions, and weight gets 10 N parts at a rate of 20 per worker of interest. Based on an average strength of 30 Nm, the minute from a rack at a distance of 0.625 m at shoulder height average relative workload for the worker described in Figure 5e.5 and Table 5e.3 would be 28% MVC. Joint loads can be estimated also from surface electromyo- graphy (EMG), which can be regarded as a response variable

Chapter 5e ● Exposure-response relationship 199 14 0 – 20 12 Shoulder moment – 40 (Nm) – 60 10 Shoulder angle (°) 8 Moment (Nm) –0.40 –0.20 0.00 0.20 0.40 0.60 0.80 6 0.00 – 0.05 4 – 80 – 0.10 – 0.15 2 –100 – 0.20 0 –120 – 0.25 –2 – 0.30 –4 –140 – 0.35 –6 –160 A Male 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Distance (meters) B Male 14 0 – 20 12 Shoulder moment – 40 (Nm) – 60 – 80 10 Shoulder angle (°) –100 –120 Moment (Nm) 8 –140 –0.40 –0.20 0.00 0.20 0.40 0.60 0.80 6 0.00 – 0.05 4 – 0.10 – 0.15 2 – 0.20 – 0.25 0 – 0.30 – 0.35 –2 C Female –4 –160 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Distance (meters) D Female Moment (Nm) 14 0 Shoulder moment –10 – 20 12 (Nm) – 30 10 Shoulder angle (°) 0.00 0.20 0.40 0.60 0.80 8 –40 0.00 – 50 – 0.05 – 0.10 6 –60 – 0.15 – 0.20 4 –70 – 0.25 – 80 – 0.30 – 0.35 2 –90 E Male 0 –100 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Distance (meters) F Male Moment (Nm) 14 0 Shoulder moment –10 – 20 12 (Nm) – 30 10 Shoulder angle (°) 0.00 0.20 0.40 0.60 0.80 8 – 40 0.00 Female – 50 – 0.05 – 0.10 6 – 60 – 0.15 – 0.20 4 –70 – 0.25 – 80 – 0.30 – 0.35 2 – 90 G 0 –100 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Distance (meters) H Female Figure 5e.4 Calculated shoulder and elbow moments due to the weight of the arm, forearm, and hand for an average male and female performing a horizontal reach at elbow (A-D) and at shoulder (E-H) heights for females (C, D, G, H) and males (A, B, E, F).

200 Chapter 5e ● Workplace adaptation for shoulder disorders 100 ANALYSIS OF JOB TASK DEMANDS MS (N-m) 80 As stated at the beginning of this chapter and shown by the above Males discussion, information about task demands is necessary for disability evaluation and work adaptation design. Collecting 60 job and worker information requires a systematic approach in two steps. Job task demands 40 The first step documents what, where, when, and how the job is performed and includes the process, equipment, procedures, and 20 environment. Females Job documentation 0 30 60 90 120 0 A thorough documentation of the job helps to ensure a sys- tematic analysis of all relevant factors and enables the analyst Figure 5e.5 Shoulder strength for four healthy young females and to identify those that contribute to stressful postures. Finding four healthy young males versus shoulder angle with elbows straight that the job involves exposures to extreme shoulder postures, for (triangles) and flexed 90 degrees (circles). example, is insufficient without information explaining what actions like reaching for a part or operating a control produce to external load.23,26,31 Generally, EMG methods are used to those postures. This information enables the analyst to recom- verify hypotheses developed using biomechanical analyses and mend possible interventions to reduce that stress. Evaluation of psychophysical studies. Electrodes are attached over one or more particular stresses, such as part weight and location, can be used of the muscles associated with the joint motion of interest and to calculate the load moment on the shoulder. connected to appropriate preamplifiers, amplifiers, data loggers, and computers. The test can be normalized with respect to a Observations maximum exertion or some other reference signal and provide a continuous real-time indication of muscle load. Further discus- Documentation procedures may need to be adapted to the type sion of EMG methods is beyond the scope of this chapter. of jobs being studied. In many settings, particularly manufactur- ing, the work is by design standardized to control work quality and production, but subtle differences from worker to worker may depend on their sizes, methods, and skill levels. A short worker, for example, may have to reach up and over, whereas a tall worker may have to reach down and under. One may choose Shoulder (Nm) 20 Total (Nm) 15 Load (Nm) Body (Nm) 10 Average 5 0 01234 A Time (s) B Figure 5e.6 (A) A worker reaching 0.625 m forward to get 10 N (2 pounds) parts from trays 0.320 m in front of her on a moving tray and a rate of 20 per minute. (B) The moment due to the weight of the body and work object are shown. Average total moment (body plus work object) is 8.4 Nm for the work cycle.

Chapter 5e ● Analysis of Job Task Demands 201 Table 5e.3 Work elements, locations, and loads for a repetitive hand transfer task Work element Elapsed time Hand location Load weight Moment load Moment body Total Reach 0.67 32.1→62.5 0 0 4.5→9.8 4.5→9.8 Grasp 0.13 62.5 0 0 9.8 9.8 Move 0.79 62.5→32.1 10 N 6.25→3.21 9.8→4.5 16.05→7.71 Wait 2.00 32.1 10 N 3.21 4.5 7.71 Position 0.36 32.1 10 N 3.21 4.5 7.71 Release 0.07 32.1 0 0 4.5 4.5 to walk around a pallet of parts, whereas another reaches across. time analyses from industrial engineering or previous ergonomic Although one worker may be able to complete work promptly assessments. Job descriptions from the personnel department and take brief rest periods, another may have trouble keeping up tend to focus on skill requirements rather than on force and and have no rest. posture patterns. Work method and time descriptions can be quite useful because they usually describe the methods and time How workers perform their jobs may change over time. allocations. Combined with information about work objects In some cases, jobs contain multiple tasks, as though each was and work stations often make it possible to predict loads and pos- two or more jobs. The documentation should include identifi- tures as described above. Because the job may have changed since cation of each task, its frequency, and its duration. Frequencies the standard was developed, work method and time descrip- and duration may vary from day to day, so it is necessary to tions should always be verified with observations or interviews. either observe the job over time as previously described or to ask Although in some cases an ergonomic job analysis has previ- the worker or supervisor to estimate the variation. ously been performed, at present such analyses are not standardized. Unless the analyst has first-hand knowledge of the An increasing trend to rotate workers among jobs occurs in job and the methods used to analyze it, each job should be many cases to maintain production schedules by cross-training inspected to verify that all necessary information was included them to deal efficiently with absenteeism and schedule changes. or that it has not changed. In other cases it is done to reduce exposure to highly demanding jobs. Generally, the analyst performs at least a cursory analysis of Video recordings all the jobs the worker performs, particularly if he or she has had a musculoskeletal injury. Still and video images have become integral parts of job analyses. Readily available low-cost digital and video cameras can now It is common to manufacture different product models or be used to collect images and transfer them into computers even products on the same production line. In some cases the where they can be viewed and edited. Freeware, such as Apple worker may have to hurry to perform all the required assembly Computers QuickTime™, can be used to play back digital films operations without rest, whereas at other times they may be able frame by frame, the most useful of which can be captured and to work quickly and rest frequently. pasted into report documents. A few simple steps will greatly improve the quality of the video data: (1) obtain permission Some jobs, such as maintenance, repair, and office work, from the worker and the employer, preferably in writing; have yet to achieve a high level of standardization and instead (2) record several representative work cycles, both to allow the typically entail two or more tasks that may be performed at worker to get used to the camera and to observe variations; irregular intervals for variable periods. These multitask jobs (3) take pictures from several angles (the view of one hand may be may require considerably more time than a standardized single- blocked by the body or other obstructions); and (4) use a tripod task job. to improve video steadiness most efficiently and least expen- sively. Video cameras often can be set up and left to run unat- For the above reasons, observations should be repeated for tended, even with intermittent pauses at specified intervals.24 several workers over time to assess job variations for those being If video recordings are not possible, the analyst may elect to studied. While interviewing workers, the analyst should antici- make periodic tours of the workplace to observe and record pate this variability. Differences from one worker and one work personally. station to the next often provide insights into how the job can be improved. Intermittent observations of worker activities are referred to as “work sampling”; statistical procedures have been described The documentation can be performed from available job for estimating confidence limits for the frequency that a task descriptions, time studies, workplace inspections and measure- occurs.17,33 To get a confidence limit of a few percent, typically ments, equipment specifications, and interviews with workers hundreds of samples are required, which may be beyond the and supervisors. To facilitate cooperation of both the worker scope of most studies. Statistical calculations are based on the and employer, it is important that the job analysis minimizes assumption that the observations are randomized. Although disruption of work activities. Because the goal is to obtain infor- generally there is sufficient variation in the work process to mation about how the job is performed under normal work allow fixed interval sampling, the analyst should make sure that conditions, minimal disruptions will help keep the worker from being distracted by the analyst. Available information may include job descriptions from the personnel department, standard work method descriptions, and

202 Chapter 5e ● Workplace adaptation for shoulder disorders observations are not synchronized from any workplace activities Table 5e.4 Basic job documentation information can that could bias the results. be obtained from existing job descriptions, interviews, observations, and physical measurements Measurements of the work station and equipment For the job Physical measurements of the work station often can be made before or after the shift or while the worker is on break. The ● Formal job title (in company documentation) employer may have engineering drawings that enable the analyst to determine key dimensions such as the height of the work ● Informal job title (among workers and supervisors at the work site) surface and the location of parts, assemblies, and controls; otherwise, it will be necessary to determine these dimensions ● Work objectives (one or more reasons that the job exists) using a tape measure. In either case it is necessary to establish reference lines or planes for these measurements. The ideal refer- ● Job tasks (all worker duties that share a common purpose; tasks may ence plane for vertical measurements for a vertical worker, for example, is the floor. The ideal horizontal reference plane is a or may not be separated in time and space) vertical plane that passes through the barrier separating the worker from the work object. For a seated worker, this is the front For each job task of the desk, whereas for a standing worker reaching into a bin of parts it is the edge of the bin. The reference plane for hori- ● Objective zontal measurements should correspond to a barrier that restricts movement from side to side. For a worker seated in a fixed loca- ● Tools and equipment (ID, size, weight) tion, this may correspond to the sagittal plane of the body; if the worker is standing and free to step side to side, then meas- ● Materials and parts (ID, size, weight) urements to either side may not be of critical importance, unless the worker is required to reach two objects with opposite hands ● Methods (step-by-step description in necessary detail of what at the same time. the worker does to perform the task) Interviews ● Work station (sketched or described with key dimensions) Worker and supervisor interviews are important sources of infor- mation, the quality of which can be greatly improved with a few ● Environment (location and conditions of job) rules32: (1) explain the purpose of the interview, (2) list the key points to be covered, (3) avoid leading questions, (4) clarify by same time or push and pull quickly, creating an inertial factor. summarizing back to the interviewee, (5) do not let the interview Direct weight and breakaway force measurement may be a start- wander into irrelevant areas, (6) protect the interviewee’s confi- ing point, but often second- or third-level methods such as dentiality, and (7) take careful notes or use an audio recording EMG or perceived exertions are also necessary. device. Interviews may be performed with one or more workers at a time. Questionnaires also can be used to obtain information Joint angles between two adjacent body segments can be from workers and supervisors, but development of a valid ques- measured using goniometers, including manual devices that tionnaire to obtain desired information about a given job can require the worker to stop while they are positioned over joints be a major undertaking in its own right. Table 5e.4 is intended and electrical devices that can be attached to a data logger or as a template for a job documentation data collection form that computer for continuous posture recordings. Gerr et al20 the user can modify to suit specific needs. described the use of manual goniometers for determining major body angles in computer users. Physical job stresses Joint angles can also be estimated from direct observations of The second part of the analysis assesses the physical job stresses. workers or indirect observations of photographs and movies. As mentioned at the beginning of this chapter, exposure-response Observations are subject to observer and parallax errors.30 entails a cascading series of relationships.4 Job demands may be Parallax errors can be minimized by aligning the viewer with characterized as a force and posture profile, as a load moment the axis of joint rotation. Often this is not possible; however, profile for a joint such as the shoulder, as the muscle activity an experienced job analyst can often do an adequate job of (measured in an EMG), or as a symptom such as localized mentally compensating for parallax errors. It is helpful to observe discomfort. or record images from several views. Measurement of posture and force Joint moments can be calculated from loads and body positions. Recall that moments are related to both the magni- Postures and forces can sometimes be measured directly using tude of the force and the distance between the force and the force gauges and goniometers. In the example shown in Figure center of joint rotation. In some cases, it may be possible to 5e.6, the major forces are due to the weight of the work object stop the worker and measure distances using a tape measure. and that of the upper limb. However, many cases are not this Sometimes distances can be estimated from dimensions of the simple: The worker may lift, push, and pull, for example, at the work place. In other cases, they may be estimated from pictures. In some cases, the forces correspond to the weight of an object lifted; in others, they correspond to the force to hold or move one object against another. Then it is necessary to simulate the workers’ actions with a force gauge. Surface EMG Surface EMG, in which electrodes are placed on the skin over the muscles of interest, is used most commonly for exposure and fatigue assessment. Electrodes are connected to preamplifiers, amplifiers, and some kind of recording device. The signals may be recorded by a portable memory device that the worker

Chapter 5e ● Analysis of Job Task Demands 203 wears or by a digital computer. The worker may be tethered to the is that it can be measured simultaneously for different parts of computer by wires or connected via radio transmitter. Because the body.14 Regional body discomfort patterns can be compared EMG values may change very quickly, it is necessary to record with workload patterns and with underlying impairments. signals over several representative cycles at high frequencies. Saldana et al37 described the use of a computer program to The volumes of data generally dictate the use of a computer and evaluate discomfort patterns in rural letter carriers. Readily appli- appropriate software for analysis. Jonsson26 and Mathiassen and cable to other types of work, this method is particularly well Winkel31 described procedures summarizing force patterns using suited for studying office workers who regularly use a computer. EMG data that indicate rest/recovery time versus work time. The investigator must be familiar with human anatomy and with the Studies by Ulin et al39 showed that perceived exertion associ- operation (including calibration) of the equipment to obtain ated with the use of a pneumatic hand tool increases with work meaningful results. An important quality of EMG is that it distance from the body and with increasing elevation above the provides information about a specific body part under real shoulder and decreasing elevation below the elbow. Krawczyk work conditions by a real worker; a limitation is that an EMG et al27 showed similar results for the hand transfer tasks. provides information about only a very small part of the body. In some cases additional channels can be used to monitor With repeated or sustained exertions, the worker may begin multiple muscle groups simultaneously, but this may be too to experience discomfort. With exertions performed over longer cumbersome and disruptive in many work situations. Some periods such as days, weeks, or years, the worker may experience EMG measurements can be performed on a subject simulating chronic symptoms. The Nordic Health Questionnaire provides a some part of or the entire job in a laboratory. Although an standardized instrument for collecting work symptom data.28 important tool, EMG is an advanced technique for use after Saldana et al37 demonstrated how a computer could be used to observations and simulations have documented the job and collect worker symptom data and how these data correspond identified the specific muscle groups. A number of commercial with work patterns. Symptom data are easy to collect and require EMG systems are now available and easy to find on the Internet; minimum equipment; the data may be highly variable from one the user is cautioned, however, to understand clearly where and worker to the next, however, and care is required to avoid bias. how the test will be used and to have adequate technical support. Event-based versus time-based observations Psychophysical responses The analysis may be “event based” with observations recorded Joint loads can be assessed also using perceived exertion,8,23 only when an event of interest occurs, such as when a worker which is affected by localized fatigue. Most commonly it is meas- reaches for or uses a work object. Joint loads are plotted as a ured using a Borg scale of relative perceived exertion (Fig. 5e.7B), function of time in Figure 5e.6, but because the times correspond but it may be assessed using visual analog scales also shown with the worker’s reaching for parts, it is an event-based analysis. in Figure 5e.7C. On average both work equally well, but some The definition of events is arbitrary: They may correspond to prefer the Borg scale while others prefer the visual analog scale.39 specific work elements as shown in Figure 5e.6, with only selected One of the important and useful features of perceived exertion work elements, or with the use of certain tools. The example shown in Figure 5e.6 is an event-based analysis in which the 0 0 Nothing at all events are work elements and straight-line extrapolations are 2 16 0.5 Very, very easy used between successive events. The selection of events is deter- 1 Very easy mined by the job documentation and the goals of the analysis. 3 10 7 2 Easy 3 Moderately hard The analysis may also be “time based” in that the forces and 4 11 8 4 Somewhat hard postures are observed continuously or at specific time intervals. 12 9 5 Hard The corresponding events are then examined to identify the work 6 factors that cause the extreme force or posture. Forces and pos- 5 13 7 Very hard tures may be estimated from observations, measured directly 8 using force gauges and goniometers, or predicted by biomechan- 14 15 9 ical models and insights. The work sampling method described 10 Very, very hard above is a time-based analysis of activities, but it could be 16 17 combined with force and posture measurements. B A Prediction of posture and forces Very Very Figure 5e.4 shows how link data can be used to estimate postures uncomfortable comfortable and forces of males and females of given percentiles at selected locations. In many cases, the analyst may mentally extrapolate work work based on observations and experience. When a tall worker is seen reaching overhead for a part, for example, it becomes obvi- C ous that a short worker or one with limited mobility will be even more challenged to perform the same task. The analyst may Figure 5e.7 Local discomfort patterns can be mapped by asking the want to report not only what was observed, but what might worker to indicate areas on a body part map as shown in A. Localized be observed for another worker. and overall discomfort and effort can be quantified using the modified Borg scale shown in B or a visual analog scale shown in C. The moments about the shoulder and elbow can be computed using the methods described above if additional quantification is desired. These values can be used to predict and compare

204 Chapter 5e ● Workplace adaptation for shoulder disorders worker endurance at the observed versus modified work stations. Tables 5e.1a, 5e.2, and 5e.4. Together this information can be Many third-party biomechanical models available for purchase used to map worker reach capabilities or envelopes and to or for download as shareware or freeware can be used to facili- calculate load moments, as shown in Table 5e.3. tate analysis of loads on the entire body or on selected body parts. One commercially available product is the University Anthropometric considerations of Michigan Three-Dimensional Static Strength Prediction Program.13 This program enables the user to enter information Figure 5e.8 shows maximum reach envelopes for 5th percentile about the location and direction of the load, at which the model female and 95th percentile male statures on horizontal work calculates moments and populations for percentiles at each major surfaces. In one case the arm is outstretched at shoulder height, joint. The user also can directly enter body part sizes and posi- and in the second case the shoulder is constrained to -60 degrees tions for a given problem. (Re. horizontal). There is nothing sacred about the 5th and 95th percentiles; universal designs that accommodate all possible WORKPLACE ADAPTATION users are preferable. As a practical matter the selection of design benchmarks is based on costs and benefits, although the cost The preceding discussion indicates that workplace adaptations of potential litigation can favor inclusion of more users in an entail reducing load moments by rearranging work objects analysis and design. In either case, it is still necessary to have and eliminating stressful postures, reducing forces themselves, or information about the size of the potential work population or reducing the time that forces must be exerted. Such adaptations a specific individual to be accommodated. It is also possible to include rearrangement of work space layout and use of lighter estimate the effective work area subject to desired posture con- tools or materials, mechanical assistance, and/or body supports. straints. The effective work area for the small female shown in Figure 5e.8d, for example, is approximately 0.48 m2. Based on a Placement of work objects straight hand, this calculation disregards any intrusion of the body into the work space. As a practical matter, the area should Ideally, work objects such as materials, parts, tools, assemblies, be reduced a minimum of 8% for a relatively lean body. The controls, and data input devices should be placed as close to reach distance and area would be further reduced if the worker the worker as possible at or near elbow height. Aforementioned must hold an object like a mouse or a power tool. Reducing the studies by Ulin et al39 found that some workers prefer to use tools reach distance by one-half hand length to allow for gripping slightly above elbow height, which may provide better visibility, would reduce the effective work area by 24% from 0.48 to 0.36 m2. whereas others prefer them slightly below, which may enable Adjusting for the incursion of the body into the work area fur- them to lean into the task at hand. Similarly, Sauter et al38 and ther reduces the work area to 0.32 m2. Of course the worker can Grandjean et al21 showed that most keyboard users prefer posi- reach farther, but it would be at the expense of increased shoul- tioning conventional keyboards at or near elbow heights, but der and/or back flexion. Although reasonable for short periods, some prefer it slightly higher or lower. Personal preferences such increased flexion may be unsatisfactory for prolonged or vary significantly from person to person. As shown in Table 5e.2, sustained work. worker size varies significantly between and within gender groups. Individual preferences also vary among workers of the same size Objects that are used continuously or frequently should have and for the same worker over the course of the day; even the best first priority for this space. For a data entry job, for example, position eventually becomes uncomfortable. these would be the keyboard, mouse, and source documents. Objects used less frequently such as a telephone, the computer Because one-size work station will not fit everyone, it is very CPU, or stored reference documents may be placed at the outer important for each worker to be able to adjust the work station limits of the reach envelope. A typical keyboard requires 0.1 m2 of to his or her own preference. Achieving this flexibility begins space, a mouse another 0.1 m space, and a standard 8.5 × 11-inch with designing equipment in ways that make such adjustments document another 0.6 m2, totaling 0.26 m2 of the available easy and convenient. If a mechanic must come to raise or lower 0.32 m. The areas required for the keyboard, mouse, and docu- a keyboard, the adjustment probably will not occur as often as ments, however, are not contiguous, and workers generally posi- needed. Workers must be trained and encouraged to adjust their tion them in a way that conforms with their body positions. work stations, with periodic inspections to make sure that they As a result the 0.32 m2 will be more than used up. are doing so. A worker’s failure to adjust a work station upon inspection may not mean a discipline problem but rather a lack The required space can sometimes be reduced by selecting of training or time, an adjustment for temporary stretch break, alternative equipment. A track ball or touch pad, for example, or equipment that is difficult or unsuitable to adjust. It is impor- would reduce the mouse area to less than 0.01 m2. Unless tant to discuss these issues with the worker. the worker uses the numeric keypad, a shorter keyboard might be substituted. By holding a document on an incline, a stand Although it is usually desirable to locate work objects close or holder can reduce its footprint. With the many choices of to the worker, it is not always possible. In many cases the job computer input devices and work stations that are now may entail work on large equipment, parts from multiple sources, available, the feasibility of these adaptations of course depends or use of several tools and controls. Work station design begins on job demands and individual capacities. Additional anthro- with a thorough knowledge of the work objective, tools, materi- pometric guidelines for design of computer work stations have als, and methods as well as worker size and strength, as shown in been published by the Human Factors and Ergonomics Society.25

Chapter 5e ● Workplace adaptation 205 1.4 1.4 1.2 1.2 1 1 0.8 0.8 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 A B 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 – 0.2 – 0.2 – 0.4 – 0.4 – 0.6 – 0.6 – 0.8 – 0.8 5% percentile female stature 5% percentile female stature elbow height = 0.99m D elbow height = shoulder height = 1.23m 1.2 C 1 1.2 0.8 1 0.6 0.8 0.4 0.6 0.2 Figure 5e.8 Reach envelopes computed 0.4 according to National Health Survey Data of 0 0.2 0.4 0.6 0.8 1 stature and relative link length data reported 0.2 0 by Drillis and Continni.16 (A and B) Side views 1.2 of someone with 5% female stature and average 0 – 0.2 body proportions with an arm outstretched at 0 0.2 0.4 0.6 0.8 1 1.2 shoulder height and the shoulder constrained to – 0.4 −60 degrees (Re. horizontal). Restricting – 0.2 shoulder flexion to −60 degrees reduces reach – 0.6 distance by 21% from 0.66 to 0.52 m and – 0.4 elbow height from 1.23 to 0.99 m. (C and D) – 0.8 Top views of the elbow height reach envelopes – 0.6 for the 5 percentile females with and without –1 shoulder constraints. (E and F) Top views of – 0.8 the elbow height reach envelopes for the –1.2 95% percentile male stature 95 percentile males with and without shoulder –1 elbow height = 1.23m constraint. For the large male, restricting F shoulder flexion reduces reach distance by –1.2 22% from 0.83 to 0.65 m and reduces elbow 95% percentile male stature height from 1.54 to 1.23 m. elbow height = shoulder height = 1.54m E

206 Chapter 5e ● Workplace adaptation for shoulder disorders The above calculations were based on standard percentiles. site at the time required. In addition to reducing inventory costs, Similar calculations can be performed based on link length these methods also reduce reaching. estimates for an individual by using the link length fractions reported by Drillis and Contini16 and displayed in Table 5e.1a or Tool weight control those reported by Dempster15 and others.13,29 Loads can also be reduced by decreasing the weight of work Minimizing the reach distance helps to minimize the load objects by using lighter tools, for example. Armstrong et al2 on the shoulder. Work that requires continuous visual feedback found that workers consistently rated hand tools weighing more may result in prolonged neck flexion, however, requiring a trade- than 18 N as “too heavy.” The weight of a work object may off between loads on the shoulder and neck. The solution otherwise be an asset; for example, the weight of a power tool for depends on the task. Most experienced keyboard users, for driving threaded fasteners or for sanding or buffing may reduce example, can work without watching their hands; however, the force required. Of course, this is true only with horizontal documents laid flat on the work surface require the worker to surfaces, when the worker is driving threaded fasteners down or look down. In many cases this problem can be solved with a sanding or polishing the top, as opposed to underneath, where document holder. It is not uncommon, particularly in medical tool weight would be a liability. Tools that work well in one billing, for the source documents to contain many pages that are situation may not work well in another. Adaptation development bound together and may require a custom holder. In some cases, requires a thorough job analysis. like fine assembly and dental work, it is necessary to bring the work in line with the eyes, often by providing arm and body Mechanical assists supports. A mechanical assist can be defined as any mechanical device that The traditional assembly line presents some special design helps to reduce the task demands on the worker. In this context challenges because it is often in continuous motion and difficult we are concerned with devices that reduce the load moments to make work stations individually adjustable (Fig. 5e.9a). Also, about the elbow, shoulder, and neck. A mechanical assist may the worker often must reach over a structure along the sides range from a complex robotic device capable of supporting high of assembly line. Space is required not only for the line itself, forces with low-force guidance to a simple work surface that but also for parts containers and tools. Parts may be stacked in relieves the worker of the need to support an object in use. Some front of, beside, or behind the worker, whereas tools may be sus- examples of mechanical assists include the following: pended overhead or mounted or laid along the side of the line. Lifts raise or lower materials to reduce bending and reaching and There have been many improvements in manufacturing meth- support work objects while they are in use. ods over the last 30 years that help to address these issues. Lean manufacturing discourages large inventories of parts that fill up the work space and increase reach requirements (Fig. 5e.9b). There is increasing emphasis on kitting of parts so that only those needed for a specific assembly are delivered to the work A B Figure 5e.9 (A) A traditional continuously moving assembly line. Parts are stored in front, beside, and behind the worker. (B) A modern “lean” line in which the parts for each operation are supplied in kits that follow the assembly on the line. The line stops until the work is complete.

Chapter 5e ● References 207 Turntables rotate materials and work objects to reduce reaching. adjustable, folding down to support the arm for highway driving Tool balancers support tools against gravity. and up and out of the way for city driving. Articulating arms may be neutrally balanced to support tools Forearm rests can also be mounted on articulating arms and resist reaction forces and may be powered to provide that adjust vertically and move freely in a horizontal plane. increased lifting capability for heavy objects. Articulating forearm rests are well suited for keyboard- and Carts may be used to support work objects while in use and to mouse-intensive jobs and for some bench assembly work. transport them from one work station to another. Mounting fixtures and brackets hold tools in convenient locations/ Forearm rests may be fashioned also from slings suspended orientations when not in use. from balancers overhead that enable the worker to move in three Work fixtures and jigs hold work objects, reduce loads otherwise dimensions while reducing loads on the shoulder. As with bal- required to hold or use them, and free one or both hands for ancers used for power tools, placement and force adjustments for performing useful work. each worker and task are very important. Work benches support the weight of work objects and should be adjustable to accommodate various heights of users and tasks. Evaluation of adaptations Tools and power tools ranging from a simple pry bar to a complex poster tool combined with an articulating arm reduce the It is important that workplace adaptations be evaluated to ascer- strength required to perform tasks. tain their effectiveness. A well-intended adaptation may increase rather than reduce work demands because it was ill-conceived or Although mechanical assists can greatly reduce physical loads improperly installed or adjusted. As a minimum, evaluations and task demands, failure to design, select, and install them should include inspection of the job. A more formal assessment properly can result in stressful postures and increased workloads. may require time- and event-based analyses of work postures and Assists must also be easily adjustable to suit each worker and forces. Worker feedback in the form of perceived exertion from task. Additional details of these devices are beyond the scope of one or more users also may be used to evaluate the intervention. this chapter but are readily available on the Internet. As a practical matter, there is very seldom sufficient control or statistical power to show a significant reduction in chronic soft Worker fitness and weight tissue complaints and impairments, but most employers continue to monitor health records for possible changes. National health survey data show that the level of obesity in our SUMMARY society is growing rapidly.12 Although fitness and weight training are the concerns of health care providers, job designers need to Resulting from job demands that exceed an individual’s understand their effects on work capacities and ability to meet job work capabilities, disability can be controlled by reducing these demands (Fig. 5e.1). Workers with low fitness levels exert less force demands through workplace adaptations or by increasing work- for a given amount of time. Load moments on the shoulder of ers’ capabilities through medical treatment and physical therapy. heavy people tend to be higher than those for a person with a low Determining disability and designing adaptations require under- body weight because their arms are heavier (Table 5e.1c). Large standing of the exposure-response relationship, which provides body masses encroach on the work space close to the body, which a framework for work factors, external workloads, internal tissue is the ideal location for many work objects. A large body mass also loads, pain, fatigue, and MSDs. Many examples of mechanical may require a worker to reach farther and to produce greater assists and body supports can be found by searching the Internet. shoulder moments than a small body mass. The treating physician Population and individual anthropometric data can be used to or therapist should be consulted regarding how the work space specify workplace layouts, equipment, tools, and procedures should be adapted for a worker with a very large body mass. that help to reduce job demands and disability. Workplace adap- tations should be evaluated to verify that they have achieved Body supports their intended effect. Body supports such as arm rests are widely used to counteract REFERENCES gravity forces on the body.1,5,18,19 In the absences of arm rests, workers often use the edge of the work bench, desk, or keyboard 1. Aaras A, Fostervold KI, Ro O, Thoresen M, Larsen S: Postural load during VDU work: a or the work object itself, padded with pillows, foam pads, pack- comparison between various work postures. Ergonomics 40(11):1255-1268, 1997. ing materials, and duct tape. Although improvised arm rests may look crude, they are often more effective than those pro- 2. 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