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

Chapter 4a ● References 105 mainly from occupational exposures, has been found to be 11. Battié MC, Videman T, Gibbons LE, Fisher LD, Manninen H, Gill K: 1995 Volvo Award influenced in large part by heredity. The clinical implications of in clinical sciences. Determinants of lumbar disc degeneration: a study relating these findings include an altered conceptualization of the etiol- lifetime exposures and magnetic resonance imaging findings in identical twins. ogy of lumbar spine degeneration. Medical imaging findings that Spine 20:2601-2612, 1995. were once commonly attributed to occupational exposures can no longer be explained as such. Current evidence suggests that 12. Bernard BP, National Institute for Occupational Safety and Health: Musculoskeletal the role of occupational loading exposures is relatively minor in disorders and workplace factors: a critical review of epidemiologic evidence for comparison with genetic influences. work-related musculoskeletal disorders of the neck, upper extremity, and low back. Publication no. 97-141. Cincinnati, OH, 1997, DHHS (NIOSH). Second, the search for risk indicators has continued to result in inconsistent findings, identifying relatively small roles for envi- 13. Bigos SJ, Battié MC, Spengler DM, et al: A longitudinal, prospective study of ronmental factors in explaining work-related back pain reporting industrial back injury reporting. Clin Orthop 279:21-34, 1992. and associated disability. These findings are contrary to earlier views that ascribed back pain incidents to excessive occupational 14. Boden SD, Davis DO, Dina TS, Patronas NJ, Wiesel SW: Abnormal magnetic- physical loading requirements (either peak or repetitive). Thus it resonance scans of the lumbar spine in asymptomatic subjects: a prospective is not currently possible to predict which workers will experience investigation. J Bone Joint Surg Am 72:403-408, 1990. back pain in a given occupation and which will experience delayed recovery. 15. Bone and Joint Decade website: www.boneandjointdecade.org, 2003. 16. Boos N, Dreier D, Hilfiker E, et al: Tissue characterization of symptomatic and Finally, although the global experience of work-related back pain reporting and associated disability varies markedly by coun- asymptomatic disc herniations by quantitative magnetic resonance imaging. try or jurisdiction, over the past decade or so, for which figures J Orthop Res 1915:141-149, 1997. are available, there has been an overall decline in some countries. 17. Boos N, Weissbach S, Rohrbach H, Weiler C, Spratt KF, Nerlich AG: Classification of This decline comes after many decades of growth. Recent trends age-related changes in lumbar intervertebral discs: 2002 Volvo Award in basic in North America indicate that incidence and disability related science. Spine 27:2631-2644, 2002. to back injury claims, and time loss claims in particular, have 18. Buchbinder R, Jolley D, Wyatt M: Population-based intervention to change back pain declined over the past 10 years or so that data have been ana- beliefs and disability: three part evaluation. BMJ 322:1516-1520, 2001. lyzed. However, this decline is part of one observed in all indus- 19. Cady LD, Bischoff DP, O’Connell ER, Thomas PC, Allan JH: Strength and fitness and trial injury and illness claims. subsequent back injuries in firefighters. J Occup Med 21:269-272, 1979. 20. Carey TS, Garrett JM, Jackman AM: Beyond the good prognosis: examination of an The phenomena of work-related back pain incident reports, inception cohort of patients with chronic low back pain. Spine 25:115-120, 2000. claims, and disability are influenced by socioeconomic, cultural, 21. Cavalli-Sforva LL, Feldman MW: Cultural transmissions and evolution: a quantitative and broad legislative and jurisdictional factors. When comparing approach. Princeton, NJ, 1981, Princeton University Press. incidence and prevalence figures between nations and jurisdic- 22. Chaffin DB, Park KS: A longitudinal study of low-back pain as associated with tions, great variations are thus observed. For this reason, the occupational weight lifting factors. Am Ind Hyg Assoc J 34:513-525, 1973. role of dominant paradigms through which back pain is viewed, 23. Cherkin DC, Deyo RA, Loeser JD, Bush T, Waddell G: An international comparison particularly as it pertains to work, and the systems through which of back surgery rates. Spine 19:1201-1206, 1994. persons file related complaints must be acknowledged. Such 24. Courtney TK, Matz S, Webster BS: Disabling occupational injury in the factors constitute inherent biases in studies of the role of occu- US construction industry, 1996. J Occup Environ Med 44:1161-1168, 2002. pational exposures that must be recognized in planning epidemi- 25. Crook J, Milner R, Schultz IZ, Stringer B: Determinants of occupational disability ologic studies and interpreting resulting data. following a low back injury: a critical review of the literature. J Occup Rehab 12:277-295, 2002. REFERENCES 26. Daltroy LH, Iversen MD, Larson MG, et al: A controlled trial of an educational program to prevent low back injuries. N Engl J Med 337:322-328, 1997. 1. Ala-Kokko L: Genetic risk factors for lumbar disc disease. 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4bC H A P T E R Compressive failure, particularly in an osteoporotic individual, occurs in this region. Clinical Biomechanics of the Spine The other major component of the anterior portion of the FSU is the intervertebral disk. The function of the disk is to dis- Malcom H. Pope tribute loads and restrain excessive motion. The disk is composed of the annulus fibrosus and nucleus pulposus. The annulus is The spine is an important structure with many conflicting made up of a series of sheets of collagen fibers, with the fibers of functions. The first function, mobility, provides the motion one sheet at a 30-degree angle relative to the neighboring sheet. necessary for the activities of daily living. The second function is Mathematical models show that with removal of the nucleus, one of support for the body segments and any load moments interval stresses ensue as a result of the compressive forces being that are applied by the worker. The third function is housing, carried through the annulus. The inner portion of the disk, in which the spinal cord and nerve roots are protected. The last the nucleus pulposus, is rich in hydrophilic glycosaminoglycans function is control, with the muscles acting through the vertebrae in young adults, but with age the nucleus pulposus becomes to precisely control the posture. progressively less hydrated. FUNCTIONAL SPINAL UNIT Animal experiments have shown that disks are avascular struc- tures and that endplate permeability decreases with age, thereby The functional spinal unit (FSU) consists of two adjacent vertebrae, decreasing disk nutrition. Motion is beneficial for intervertebral the interposed vertebral disk, and adjoining ligaments. The motion disks. Solute transport and metabolism are both improved by segment can be divided into anterior and posterior components. spinal motion, and intermittent motion is less effective than The anterior components are the vertebral bodies, the disk, and continuous motion. Aging usually results in disk degeneration. the attached ligaments; all the remaining structures are posterior components.19 Degeneration of a disk reduces its proteoglycan content and thus its hydrophilic capacity. As the disk becomes drier, its elastic- The FSU is a structure in which the disk acts as a spring, the ity and its ability to store energy and to distribute loads gradually facet joints as a pivot, and the posterior ligamentous complex as decreases. Most disk herniations occur in the fourth decade of life, another spring. Experiments have shown that the FSU exhibits and herniations are found in 15 to 30 of autopsy specimens. coupled motion in which vertical translation also results in complex movements in other directions. The anterior elements of the FSU The intervertebral disk exhibits creep, which means that the have a support function and a function of impact absorption, disk continues to deform under a constant load. This time- whereas the posterior elements control motion. dependent behavior comes from the fluid flow of the disk under an applied load and from the inherent viscoelastic behavior of Anterior portion the collagen and proteoglycan matrix. Time-dependent behavior has been demonstrated both in vivo by Keller et al8 and in vitro The major structural part of the anterior portion of the FSU by Kazarian.7 The studies of Eklund and Corlett3 and Krag et al10 consists of the vertebral bodies. These bear mainly compressive indirectly measured the change in overall height of the subjects. loads and are progressively larger caudally as the weight of the The diurnal loss was about 17 mm. Kazarian7 noted that a degen- upper body increases (Fig. 4b.1). Therefore, the vertebral bodies erate disk had a higher rate of deformation and the creep curve in the lumbar region are bigger than those in the thoracic stabilized sooner. and cervical regions. Compressive strength concomitantly gradually increases from the cervical spine down to the lumbar Virgin17 was the first to suggest that the nucleus pulposus acts spine. Overall, the vertebrae are six times stiffer than the disks, hydrostatically to pressurize the disk and thus stabilizes the FSU. three times thicker than the disks, and suffer half the deforma- In a nondegenerate disk, nucleus pressure is redistributed as ten- tion of the disks. The vertebrae are very important in shock sion in the annulus layers. Normal disk pressure is about 1.5 absorption. Under compression, endplate deformation precedes times the compressive load divided by the cross-sectional area. the expelling of hematopoietic contents from the vertebrae Pressure is higher in the disk center and decreases toward the themselves. exterior. Nachemson15 reported that disk pressure is different in various positions or maneuvers (Table 4b.1). Andersson et al1 The vertebrae are an expression of Wolff’s law inasmuch as the found in vivo that intradiskal pressure increased linearly with an trabeculae are oriented to resist the vertical compression forces increase in both trunk load and trunk moment. Disk pressure and tensile forces through the spinous and transverse processes was found to be high in unsupported sitting but decreased caused by muscle and ligament attachments. There is a zone significantly with the use of a backrest inclination greater than of relative weakness anteriorly because of a lack of trabeculae. 110 degrees, with the use of lumbar supports, and with the use of armrests. The tensile stress in the annulus fibrosus due to disk pressure in the thoracic spine is less than that in the lumbar spine because the higher ratio of disk diameter to height in the thoracic disks reduces the circumferential stress.11 Posterior portion The posterior portion of the FSU has a primary role of guiding its movement. The type of motion possible at any level is

108 Chapter 4b ● Clinical biomechanics of the spine Vertebral level C3 C4 C5 C6 C7 T1 T2 T3 T4 T5 T6 Messerer, 1880 T7 Perry, 1957 T8 Bell et al, 1967 T9 T10 T11 T12 L1 L2 L3 L4 L5 0 2000 4000 6000 8000 (450 lbf) (900 lbf) (1350 lbf) (1800 lbf) Compression strength in newtons (pound force) Figure 4b.1 Vertebral compression strength at a slow loading rate. (Modified from White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, WB Saunders.) determined by the orientation of the facets of the FSU to the large range of motion, which is necessary for the activities of transverse and frontal planes. This orientation changes throughout daily living. Except for the facets of the two uppermost cervical the spine (Fig. 4b.2). vertebrae (C1 and C2), which are parallel to the transverse plane, the cervical facets are oriented at 45 degrees to the transverse Other structures that influence motion of the spine are the rib plane and are parallel to the frontal plane (Fig. 4b.2). The load- cage, which limits thoracic motion, and the pelvis. The cervical bearing function of the facets at all spinal levels is significant. spine, the most mobile region of the spine, affords the head a

Chapter 4b ● Functional spinal unit 109 Table 4b.1 Loads on the L3 disk calculated from joints play an important role in resisting shear forces. In addition, intradiskal pressure measurements in a 70-kg man Farfan5 showed that 40% of the torsional strength of the FSU come from the facet joints, and Lorenz et al12 suggested that 25% Position, Maneuver Load (N) of the axial load bearing is from these structures. Supine (awake) 250 Ligaments Supine (semi-Fowler) 100 Supine (traction, 500 N) The spine ligaments function in conjunction with other elements Sitting (unsupported) 0 of the FSU as stabilizers and check reins. They are tensile elements Standing (relaxed) 700 that can fatigue, and they do contain pain fibers. The overall Coughing 500 load deflection curve on the FSU is nonlinear, being reflective of Straining 600 ligament behavior. Extension loads the anterior ligaments and 600 flexion loads the posterior elements. Load sharing between the facets and the disk varies with the posi- During flexion, the interspinous ligaments have the greatest tion of the spine. The loads on the facets are very high, peaking strain, followed by the capsular ligaments and the ligamenta flava, at about 30% of the total load when the spine is hyperextended.9 whereas in extension the anterior longitudinal ligament bears the They are also quite high during forward bending coupled with greatest strain. During lateral flexion, the contralateral transverse rotation.4 The facets through the vertebral arches and intervertebral ligament is strained the greatest, followed by the ligamenta flava and the capsular ligaments. The capsular ligaments bear the most A 0˚ Cervical 45˚ (C3-C7) Figure 4b.2 Orientation of the facets of the B 20˚ Thoracic intervertebral joints. (A) In the lower cervical spine the facets are 45 degrees to the transverse plane – 45˚ and are parallel to the frontal plane. (B) The facets of 60˚ Lumbar the thoracic spine are oriented at 60 degrees to the transverse plane and at 20 degrees to the frontal plane. Orientation of (C) The facets of the lumbar spine are oriented at the facets to 90 degrees to the transverse plane and at a 45 degree the frontal plane angle to the frontal plane. (From White AA, Panjabi MM: Clinical biomechanics of the spine, 1991, JB Lippincott.) C 90˚ Orientation of the facets to the transverse plane

110 Chapter 4b ● Clinical biomechanics of the spine strain during rotation. The ligamentum flavum, which connects independently of the rest of the cervical spine, but motion below two adjacent vertebral arches longitudinally, is an exception in its C1 involves the entire cervical spine. The facets guide the motion, behavior because it contains a large percentage of elastin. The and as a result flexion-extension is coupled with transverse trans- elasticity of this ligament is therefore very high. This allows it to lation, lateral flexion with rotation (Fig. 4b.4), and rotation with contract during extension of the spine and elongate during flexion. axial translation. In the thoracic region, rotation is associated with In a neutral position, the ligamentum flavum is under tension as lateral flexion, especially in the upper thoracic region. In this a result of its elastic properties. Because it is located at a distance case, the vertebral bodies generally rotate toward the concavity from the center of motion in the disk, it prestresses the disk and of the lateral curve.18 Coupling of rotation and lateral flexion thus adds to overall stability. occurs in the lumbar spine, with the vertebral bodies rotating toward the convexity of the curve.13 KINEMATICS KINETICS The range of motion of the spine varies from level to level. White and Panjabi19 summarized these data (Fig. 4b.3). Flexion The basic building materials of the spine are the vertebral bodies, and extension are about 4 degrees in the upper thoracic, about which take the loads of compression, shear, and bending, and the 6 degrees in the midthoracic, and about 12 degrees in the lower muscles which act as the building blocks in tension. The muscles thoracic segments. This increases in the lumbar motion segments position and stabilize the spine. Without muscles, the ligamentous to a peak of 20 degrees at L5-S1. Lateral flexion varies from level spine buckles under loads of as small as 2 kg. In general, the to level quite markedly but is greatest in the lower thoracic seg- muscle electrical activity electromyographic (EMG) amplitude is ments and L3-L4 (8 to 9 degrees). In the upper thoracic segments directly proportional to the moment arm of the muscle line of the range is 6 degrees. Rotation is greatest in the upper segments action from the center of rotation. We can investigate the role of of the thoracic spine (9 degrees). The range of rotation is minimal muscle around the periphery through a free-body analysis in which, in the lumbar spine because of facet orientation. The lumbar spine mathematically at least, the body is cut in two and the forces and is susceptible to injury from rotation. moments are resolved across that cut surface. Forces are estimated from the electromyographic signals. In complex postures, very high There have been reports of coupled motion throughout the antagonistic activity occurs. Loads are also produced by body spine. Coupling refers to a primary motion in one direction lead- weight, prestress from ligaments, and externally applied loads. ing to a secondary motion in another. For example, C1 moves 0˚ 10˚ 20˚ 0˚ 10˚ 20˚ 0˚ 10˚ 20˚ OC - C1 Figure 4b.3 A composite of representative C1 -2 values for type and range of motion at 2-3 different levels of the spine. (Modified from 3-4 White AA, Panjabi MM: Clinical biomechanics 4-5 of the spine. Philadelphia, 1991, JB Lippincott.) 5-6 6-7 C7 - T1 T1 - 2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9 - 10 10 - 11 11 - 12 T12 - L1 L1 - 2 2-3 3-4 4-5 L5 - S1 Flexion- Lateral Rotation extension flexion

Chapter 4b ● Kinetics 111 Neutral: OCC – C1 1.3 Nm (0.6 – 1.5) C7 – T1 1.2 Nm (0.5 – 2.2) Left lateral Neutral Right lateral Slight flexion: flexion flexion OCC – C1 Figure 4b.4 Coupled motion during lateral flexion is depicted 1.4 Nm schematically. When the head and neck are flexed to the left, the spinous processes shift to the right, indicating rotation. The converse (0.8 – 1.7) is also illustrated. (Modified from White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, JB Lippincott.) C7 – T1 3.7 Nm (3.0 – 6.2) Because the lumbar spine is the main load-bearing area and the Figure 4b.5 Extension and flexion moments around the axes of most common site of pain, studies have focused on this region. motion of the atlantooccipital (OCC-C1) joint and the C7-T1 motion Loads on the cervical spine are mainly produced by the weight segment (marked with Xs) are presented for five positions of the head: of the head, the activity of the surrounding muscles, the inherent extreme flexion, slight flexion, neutral, head upright with the chin tension of adjacent ligaments, and the application of external tucked in, and extreme flexion. Values shown are the medial and range loads. Investigations in vivo confirm that physiologic loads are for seven subjects: Negative values indicate extension moments. The lower than those on the thoracic and lumbar spines. arrows represent the force vectors produced by the weight of the head. (Modified from Harms-Ringdahl K: On assessment of shoulder exercise However, quite large loads on the cervical spine have been and load-elicited pain in the cervical spine. Biomechanical analysis of calculated during neck flexion, particularly in the lower cervical load-EMG-methodological studies of pain provoked by extreme position. motion segments. Harms-Ringdahl6 calculated the bending Thesis, 1986, Karolinska Institute, University of Stockholm.) moments generated around the axes of motion of the atlantooc- cipital joint and the C7-T1 motion segment with the neck in Figure 4b.6 The relative loads on the third lumbar disk for living flexion, neutral position, and extension (Fig. 4b.5). The load on subjects in various body positions are compared with the load during the junction between the occipital and C1 was lowest during upright standing, depicted as 100. (Modified from Nachemson A, extreme extension and highest during extreme flexion. The load Elfström G: Intravital dynamic pressure measurements in lumbar discs: on the C7-T1 motion segment was low with the neck in the neu- a study of common movements, maneuvers and exercises. Stockholm, tral position but tucked in (ranging from an extension moment 1970, Almqvist & Wiksell.) of 0.8 Nm to a flexion moment of 0.9 Nm). The load increased substantially during slight flexion (reaching 6 Nm). Moroney et al14 studied subjects who resisted loads. Calculation of the maximum (compressive) reaction forces on the C4-C5 motion segment ranged from 500 to 700 N during flexion, rotation, and lateral bending and rose to 1100 N during extension. Body position also affects the magnitude of the loads on the lumbar spine. These loads are minimal during well-supported reclining, remain low during relaxed upright standing, and rise during sitting (Fig. 4b.6). Trunk flexion increases the load by increasing the forward- bending moment on the spine. The forward inclination of the spine also makes the disk bulge on the concave side of the spinal curve and retract on the convex side. Hence when the spine is flexed, both compressive and tensile stresses on the disk increase.1 Nachemson and Elfström16 and Andersson et al2 also showed that during relaxed unsupported sitting, the loads on the lumbar spine are greater than during relaxed upright standing. In this position the pelvis is tilted backward and the lumbar lordosis straightens the upper body, thereby creating a longer lever arm for the weight of the trunk.

112 Chapter 4b ● Clinical biomechanics of the spine A B C D E Figure 4b.7 Influence of backrest inclination and Disk pressure back support on loads on the lumbar spine in terms of pressure in the third lumbar disk during supported sitting. (A) Backrest inclination is 90 degrees, and disk pressure is at a maximum. (B) The addition of lumbar support decreases disk pressure. (C) Backward inclination of the backrest to 110 degrees but with no lumbar support produces less disk pressure. (D) The addition of lumbar support with this degree of backrest inclination further decreases the pressure. (E) Shifting support to the thoracic region pushes the upper part of the body forward, moves the lumbar spine toward kyphosis, and increases disk pressure. (Modified from Andersson GBJ, Ortengren R, Nachemson A: Clin Orthop 129:156-164, 1977.) The loads on the lumbar spine are lower during supported REFERENCES sitting than during unsupported sitting because part of the weight is supported by the backrest. Backward inclination of the backrest 1. Andersson GBJ, Ortengren R, Nachemson A: Intradiscal pressure, intra-abdominal and a lumbar support further reduce the loads (Fig. 4b.7).2 pressure and myoelectric back muscle activity related to posture and loading. Clin Orthop 129:156-164, 1977. Because user requirements vary, the kinds of chairs available also vary widely. Regardless of use, however, it is important to be 2. Andersson GBJ, Ortengren R, Nachemson A, Elfstrom G: Lumbar disc pressure and able to adjust any chair to meet the basic anthropometric dimen- myoelectric back muscle activity during sitting. I. Studies on an experimental chair. sions of the worker. A proper seat height is desirable and should be Scand J Rehabil Med 6:104, 1974. adjustable for the individual user. The seat surface should be 3 to 5 cm below the knee-fold when the lower limb is vertical. Foot sup- 3. Eklund JAE, Corlett EN: Shrinkage as a measure of the effect of load on the spine. ports can be used with higher chairs. The width of the seat should Spine 9(2):189-194, 1985. be sufficient to accommodate the user. It must be possible to use the backrest, so the seat pan should not be too deep. Pressure 4. El-Bohy AA, King AI: Intervertebral disc and facet contact pressure in axial torsion. should be avoided on the back of the thigh near the knees. In SA Lantz, AI King, eds: Advances in bioengineering. New York, 1986, American Society of Mechanical Engineers, pp. 26-27. Lifting creates the highest loads on the lumbar spine, and these are the occupational exposures with the greatest incidence 5. Farfan HF: Mechanical disorders of the low back. Philadelphia, 1973, Lea & Febiger. of low back pain injury reports. The key to prevention is to reduce 6. Harms-Ringdahl K: On assessment of shoulder exercise and load-elicited pain in the the load moment, which means reducing either the magnitude of the load, the distance from the body, or both. Therefore, if objects cervical spine. Biomechanical analysis of load-EMG-methodological studies of pain of the same weight, shape, and density but of different sizes are provoked by extreme position. Thesis, 1986, Karolinska Institute, University of held, the lever arm for the force produced by the weight of the Stockholm. object is longer for the larger object and the bending moment on 7. Kazarian L: Dynamic response characteristics of the human vertebral column: an the lumbar spine is greater (Fig. 4b.7). experimental study of human autopsy specimens. Acta Orthop Scand Suppl 146, 1972. DISCUSSION 8. Keller L, et al: In vivo creep behavior of the normal and degenerated porcine intervertebral disc-a preliminary report. J Spinal Disorder 1(4):267-278, 1989. The spine has functions of load bearing, protection of neural 9. King AI, Prasad P, Ewing CL: Mechanism of spinal injury due to caudocephalad elements, and mobility yet stability. The FSU, which is the basic acceleration. Orthop Clin North Am 6:19, 1975. unit, exhibits coupled motion. It is composed of the anterior com- 10. Krag MH, Cohen MC, Pope MH: Load-induced changes in human intervertebral disc ponents (vertebral body, disk, pedicles, and ligament), and the height in-vivo: a new and closer look. Orthop Trans 9(3):516, 1985. remainder make up the posterior elements. Motion, which is largely 11. Kulak RF, Schultz AB, Belytschko T, Galante J: Biomechanical characteristics of verte- controlled by the facet, varies between regimes. Flexion-extension bral motion segments and intervertebral discs. Orthop Clin North Am 6:121, 1975. is high in the lumbar spine, but rotation is minimal. Loads in 12. Lorenz M, Patwardhan A, Vanderby R: Load-bearing characteristics of lumbar facets the spine are a function of body mass, muscle activity, prestress, in normal and surgically altered spinal segments. Spine 8:122, 1983. and external loads. The latter is particularly important in the 13. Miles M, Sullivan WE: Lateral bending at the lumbar and lumbosacral joints. lumbar spine. Anat Rec 139:387, 1961. 14. Moroney SP, Schultz AB, Ashton-Miller JA: Analysis and measurement of neck loads. J Orthop Res 6(5):713-720, 1988. 15. Nachemson A: Lumbar interdiscal pressure. In MIV Jayson, ed: The lumbar spine and back pain. London, 1987, Churchill Livingstone, p. 191. 16. Nachemson A, Elfström G: Intravital dynamic pressure measurements in lumbar discs: a study of common movements, maneuvers and exercises. Stockholm, 1970, Almqvist & Wiksell. 17. Virgin WJ: Experimental investigations into the physical properties of the intervertebral disc. J Bone Joint Surg 33B:607-611, 1951. 18. White AA: Analysis of the mechanics of thoracic spine in man. An experimental study of autopsy specimens. Acta Orthop Scand Suppl 127:1-105, 1969. 19. White AA, Panjabi MM: Clinical biomechanics of the spine. Philadelphia, 1991, JB Lippincott.

4cC H A P T E R have some specific properties (sensitivity and specificity) as well as those depending on the prevalence of the disease considered Initial Evaluation of the (predictive value) in the population being evaluated. Basically, signs and symptoms (or any other test) with very high sensitivity Low Back Region allow the clinician to rule out the target disease when the test is negative. On the contrary, when the specificity of a test is extremely high, a positive result “rules in” the target disease.21 Marek Szpalski, Federico Balagué, Robert Gunzburg, HISTORY and Dan M. Spengler Two reviews of patient histories reported that although 2% to 3% Although patient evaluation and management have been clearly of the causes of low back pain are nonmechanical, these etiologies improved by the explosive growth in technology over the past must be considered most seriously and diagnosed quickly.20,22 All decades, the hallmark of patient assessment continues to reside the factors that might be relevant because of their association in the fundamentals of the history and physical examination. with increased risk of cancer, infection, or other complications The information provided in this chapter emphasizes the impor- should be included in the history.20 tance of these basic skills to attempt to motivate the reader to continue to improve and update this important knowledge area. In a study of almost 2000 back pain patients, Deyo21 found The focus of this chapter is the clinical assessment of patients that no cancer was identified among those under age 50 without who seek an evaluation of low back pain, with an emphasis on a history of cancer, unexplained weight loss, or failure of conser- occupational aspects. vative therapy (combined sensitivity of 100%). The elements suggesting a diagnosis of specific low back pain are commonly Another relevant aspect that has become increasingly important designated in the literature as red flags (Table 4c.1).6 in the last decades is the point of view of the patients. An impor- tant volume of literature devoted to this topic has been reviewed Concluding that a patient suffers from “nonspecific low back recently. In their systematic review of qualitative and quantitative pain” once the clinician has reasonably excluded red flags seems studies, Verbeek et al72 highlighted the major patient expectations, to be rather unsatisfactory for most health care providers, who specifically diagnosis, instructions, and interpersonal management. do not believe nonspecific low back pain to be one condition.42 This information is important for the individual clinician. It has been shown, moreover, that a comprehensive medical assessment is not predictive of return to work after an episode of It is important to remind the clinician that the variables occupational low back trouble.34 elicited by history taking and through a clinical examination For all patients who are examined for an evaluation of low back pain with or without sciatica, a history of the present illness should be completed, including information regarding the nature Table 4c.1 Red flags for potentially serious conditions Possible fracture Possible tumor or infection Possible cauda equina syndrome From medical history: Saddle anesthesia Recent onset of bladder dysfunction such as Major trauma such as vehicle accident Age over 50 or under 20 or fall from a height History of cancer urinary retention, increased frequency, or Constitutional symptoms such as recent fever or chills overflow incontinence Minor trauma or even strenuous lifting Severe or progressive neurologic deficit in the (in older or potentially osteoporotic or unexplained weight loss lower extremity patients) Risk factors for spinal infection: recent bacterial infection Unexplained laxity of the anal sphincter From physical examination: (e.g., urinary tract infection) intravenous drug abuse, Perianal/perineal sensory loss or immune suppression (from steroids, organ Major motor weakness: quadriceps transplantation, or human immunodeficiency virus infection) (knee extension weakness); ankle plantar Pain that worsens when supine; severe nighttime pain flexors, evertors, and dorsiflexors (footdrop)

114 Chapter 4c ● Initial evaluation of the low back region of symptom onset. The absence of sciatica or femoral nerve radic- in the morning or in the evening? Is the pain predictable or ular pain makes a clinically important disk herniation very unlikely erratic? Is the patient’s sleep pattern disrupted because of night (sensitivity about 0.95 and specificity 0.88).21 pain? Although night pain can be associated with various forms of malignancy or inflammatory disorders, it can also reflect clin- In addition, the examiner should document various treatment ical depression or be associated with psychosocial issues. approaches and the effects of the treatments on symptoms. The reason for the evaluation and any anticipated outcomes must be The relationship of various activities to the pain complaints understood in advance by both the physician and the patient. should be discussed as well. Pain that increases with walking If the evaluation is for an independent medical evaluation, for short distances yet disappears rapidly with sitting or lying can rep- example, the patient needs to understand its purpose of provid- resent a typical pattern in a patient with lumbar spinal stenosis. ing an independent objective assessment for a third party and A clinical diagnosis cannot be advanced solely on the basis of that treatment is not included. The evaluation may be to assist the pain pattern, however, because of the wide variability of clin- another physician in patient management or solely to provide an ical symptoms in most disorders that result in low back pain. insurance company or a workers’ compensation carrier with a diagnosis and recommendations. When related to swirling litiga- When interviewing a patient with low back pain that has been tion and compensation issues, a history must usually be more present for more than 3 months, the physician should com- detailed than one obtained solely to diagnose symptoms and pletely review the patient’s systemic symptoms, including fever, manage a patient. If a patient falls at home and seeks evaluation, chills, night sweats, weight loss, and lethargy, along with any for example, the history might be succinct and relate only the type sources of infection, whether systemic or not, such as a localized and distance of the fall. In a contested on-the-job injury encounter, cutaneous abscess. Gastrointestinal symptoms are relevant the details may be more important for dispute resolution. Was the because such disorders can actually occur concomitantly with low fall witnessed? Did the employee return to work? For how long? back symptoms and because so many patients take large doses of Is an attorney involved? Who are the physicians or others who salicylates or nonsteroidal antiinflammatory agents, which can have evaluated the patient? Has the employee had a previous lead to significant gastrointestinal bleeding.53 Genitourinary injury? Has an impairment been recorded previously? symptoms are reviewed also, because bladder dysfunction can be associated with pressure on the spinal cord or cauda equina. An interview with a patient who is involved in litigation can Although such symptoms are more commonly related to causes be facilitated by having the referring person summarize the out- other than neural compression, an early recognition of a change comes desired from the consultation. In addition, a succinct in bladder habits may signal a subtle increase in pressure on the summary of the events to date should be provided to serve as a neural elements.5 When genitourinary symptoms are present, the template for review during the patient interview. Information pro- physical examination should include a well-documented rectal vided by the referral source does not replace the need for a good examination. A cystometrogram and a urologic consultation history; it only highlights the issues from another perspective. may be necessary to clarify the nature of these problems.5 Female patients should be questioned regarding any changes in bleeding The opening aspects of the history should focus on the pres- patterns or pain related to menstruation, and those with persist- ent illness. The examiner must not lead patients into answers by ing back complaints should be evaluated by their gynecologists. the use of “closed” questions, such as “Does your back pain radi- ate to the posterior of your thigh, calf, and foot?” Patients may Medications taken by the patient should also be recorded. If the often answer yes to these questions even though they may not patient has been taking multiple medications in the past for back understand what was asked or the relevance. A much better strat- pain, the associated clinical response should be noted. Other back egy is to ask the patient to describe the pain. What makes the pain treatment approaches, including the patient’s pain-free interval better or worse? These questions can amplify the pain drawing after an intervention such as steroid dose packs, epidural steroid that is gathered before the history and physical examination.9 injections, or physical therapy, should be noted as well. This tool is helpful to maintain in the patient’s file to compare over time or to establish the patient’s pain pattern at the time of Psychosocial and economic issues associated with the low back evaluation. symptoms should be reviewed. Life stressors, litigation, compen- sation, and other secondary gain parameters would likely not have In addition, recording a few notes for later dictation, the “caused” the pain, but such issues can certainly maintain the physician should also observe the psychologic, physical, and chronicity of symptoms in specific cohorts of patients. A system- emotional behavior of the patient throughout the interview atic review of psychologic factors as predictors of chronicity and examination. Loss of eye contact, change in voice tone, or disability highlight the limits of the available evidence, or excessive movement on the examining table should be noted, but the roles of distress/depressive mood and, to a lesser extent, because these nonverbal cues may be equally or more important somatization are underlined. As discussed in greater detail in than the actual words spoken. Signs suggesting a clinical depres- Chapter 2, the role of coping strategies and fear avoidance deserve sion should be noted also because depression can be commonly further research.52,73 encountered as both a primary and a secondary disorder in patients complaining of low back pain. Slurred speech or an impressive In recent years a list of red flags and treatment matrices have knowledge of pain medications should be noted also to provide been enlarged to include cognitive and behavioral approaches clues to potential alcohol or medication abuse, the latter of which into the early management of acute low back pain. “Yellow flags” is quite common in patients who complain of chronic back can be evaluated by means of six open questions that should be symptoms.9,61 phrased in the health care provider’s own words: 1. Have you had time off from work in the past with back pain? Pain patterns should also be noted. Does the pain intensity 2. What do you understand to be the cause of your back pain? stay the same throughout the 24-hour day, or is it better or worse 3. What are you expecting will help you?

Chapter 4c ● Physical examination 115 4. How are your employer, coworkers, and family responding to patient and doctor. They must be understood in the context of your back pain? the patient’s history and offer only a psychologic “screener,” not a complete psychologic assessment. Finally, they are not on their 5. What are you doing to cope with back pain? own a test of credibility or veracity, nor are they a reason to deny 6. Do you think that you will return to work? When?40 appropriate physical treatment.48 A study showed that with regard to return to work in patients with acute low back pain, the predic- Moreover, “blue” flags (psychosocial aspects of work) and tive value of the nonorganic symptoms or signs (independently “black” flags (employer-specific and global) aimed at evaluating or combined) was rather poor.28 other socioeconomic environmental factors have been described in the last few years.31 The patient should be suitably attired for the examination to provide for privacy but also to facilitate a complete musculoskele- The past medical history should be completed to include any tal evaluation. Together with a sheet for the supine and prone por- diagnostic assessments, treatment approaches not previously tions of the examination, the standard patient gown that is open noted, and doctors or others who have evaluated or treated the in back is quite appropriate. The physical examination should be patient for low back and other medical problems. The length of complete but also age and complaint related. Although not an any pain-free interval after previous surgical procedures should essential portion of the examination in an 80-year-old patient also be documented. Short-term relief after major surgery may with back pain after a minor fall, chest expansion, for example, occur after procedures that may not have been clearly indicated. is clearly important in a 20-year-old man with an insidious onset Other causes can include an operation performed at the wrong of low back pain over a long period of time. Decreased chest spinal level, an inaccurate diagnosis, an associated medical disor- expansion (less than 2.5 cm) in such a patient could suggest the der with referred low back symptoms, and a pain-prone patient diagnosis of ankylosing spondylitis. who tends to amplify symptoms. A study showed that a screening system led by two physiother- A comparison of the existing occupational health guidelines apists resulted in a clinical and economic improvement in the for the management of low back pain revealed that all the pub- care of those suffering from acute low back pain.49 The physical lished guidelines distinguished specific and nonspecific cases and examination is divided into five components based on the posi- consistently recommended a clinical history to identify relevant tion of the patient, beginning with the patient standing. physical and psychosocial workplace factors and a physical examination including neurologic screening. Red and yellow flags Patient standing are highlighted by most of the guidelines.63 The lumbar spine examination begins with the patient standing. PHYSICAL EXAMINATION The physician should observe the general configuration of the spine to detect any lateral curvatures, kyphosis, or excessive A physical examination is one among many patient expectations72 lordosis. Patients with lumbar paraspinous spasms frequently that permits the physician to assess the patient and record the have a pelvic list that should be noted. In patients with lumbar observations. Objective findings, including deep tendon reflexes disk herniation, it has been demonstrated that although not asso- and circumferential measurements of the calf and thigh to deter- ciated with the location of nerve root compression, the direction mine swelling or atrophy, represent the most important parameters. of lumbosacral scoliotic list is related to the side of disk hernia- Less helpful, subjective, physical examination findings include tion.64 In young adult males with low back pain, chest expansion supine straight leg raising (unless done in the sitting position as should be measured with a cloth tape because expansion less well) and range of motion, the least reliable of all determinants.3 than 2.5 cm suggests an inflammatory process such as ankylosing Unfortunately, range of motion is still used, although to a lesser spondylitis. degree, for impairment ratings as suggested in the American Medical Association guidelines. After observing the spine orientation in the erect patient, the physician should ask him or her to flex forward, a step particu- Inappropriate physical examination findings are important to larly important in adolescents to detect early lateral curvatures of record also. A certain number of inappropriate physical signs have the spine. To assess the range of motion of the lumbosacral been described and are often referred to as “Waddell’s signs.” Too spine, the physician should stand behind the patient and observe often, physicians consider the presence of three or more of these the lumbar paraspinous muscles. Any eccentric contractions of findings as an alert that the patient may be attempting to amplify the musculature suggest lumbosacral paraspinous spasms; limited them for secondary gain. It is important to note, however, that the motion without evidence of such eccentric contractions might presence of inappropriate physical findings does not exclude the suggest a lack of patient cooperation even though there are other presence of a pathologic process and may be due to factors other possibilities (such as a congenital block or previous fusion). than attempted malingering. This illness behavior may be linked to fear of reinjury, misunderstanding of instructions, other psycho- Forward and lateral flexion and extension of the lumbar spine logic issues, and other incident issues. The onus is therefore on the should be observed. Normal patients should be able to bend physician to recommend the appropriate diagnostic studies. forward nearly to touch their toes and to the sides to touch the fibular heads, but extension of the spine is extremely variable. Main and Waddell48 discussed the theoretical misunderstand- In general, pain increased by flexion suggests lumbar disk abnor- ings of the behavioral signs in clinical practice and in the malities and pain with extension suggests degenerative changes medicolegal context. We reproduce here some of the authors’ involving posterior elements of the spine, lumbar spinal stenosis, conclusions and recommendations. As “behavioral responses to or both. Occasionally, patients with lumbosacral paraspinous examination,” these signs are a form of communication between

116 Chapter 4c ● Initial evaluation of the low back region spasm can flex forward reasonably normally but have difficulty Figure 4c.1 Sitting straight leg raise test. The patient leans back in returning to the erect position. Such patients may accomplish this the “tripod” sign, indicative of true sciatic tension. move in a two-phase recovery by flexing the knees and extending the hips without motion in the lower back. The most important portion of the sitting examination is the distracting straight leg raise (SLR) test (Fig. 4c.1). The SLR test The true value and reliability of flexibility assessment is, how- has shown to be adequate in healthy subjects when performed ever, dubious. The reliability of lumbar flexion and extension within a complete physical examination.33 During this lifting of measured with an electronic inclinometer within a complete phys- an extended symptomatic leg in the sitting position, patients ical examination was evaluated in a group of normal volunteers. with herniated disks and true symptoms of sciatic tension arch The intrarater and interrater reliability for flexion were, respec- backward and complain of pain in the buttock, posterior of the tively, 0.48 and 0.56, whereas the same values for extension were thigh, and calf. Patients who do not have true sciatic tension do 0.53 and 0.37, respectively.33 In older patients, the range of motion not recognize this as a sciatic tension test and therefore have no of the cervical spine should also be assessed because degenerative symptoms. For the patient who complains of pain in the neck osteoarthritis of the cervical spine occasionally results in low back as well as the lower back, the strength and reflexes of the upper complaints. A study including 27 patients suffering from lower extremities can be evaluated while he or she is sitting. back pain and unilateral single nerve root symptoms, 14 patients with multilevel nerve root symptoms, and 10 control subjects Patient supine showed that low back pain correlated significantly with restriction of anteroposterior spinal flexion measured with a computerized With the patient supine on the examining table, the physician triaxial potentiometric analysis system.54 uses a standard tape to measure the true length of the limbs from the anterior superior spine to the medial malleolus on both sides. After observing the range of motion, the physician should Although significant discrepancies (more than 2.5 cm) in limb percuss the spine to detect any localized tenderness, a subjective lengths can result in mild compensatory scoliosis and low back reaction. This test has little value if the patient has tenderness at discomfort, these associations are uncommon. multiple areas, but consistent localized tenderness over the mid- line of the spine may suggest inflammatory diskitis (or fractures, The physician should observe the thigh and leg muscles for tumors, and so forth). The costovertebral angle should be palpated; early signs of atrophy. In addition, the physician should use a tenderness in this area suggests a genitourinary problem such as cloth tape to measure the circumferences of both thighs one pyelonephritis. handbreadth above the patella and those of both calves one handbreadth below the patella. Discrepancies greater than 2 cm Patients should next be asked to walk on their heels and then again are probably significant and suggest muscle atrophy. toes to assess the overall strength of the dorsiflexors (L5) and plantar flexors (S1) of the ankle. In particular, the extensor hallucis For the standard ipsilateral SLR maneuver, the physician stands longus muscles should be observed when the patient is walking on to the patient’s right, places the left hand on the patient’s patella the heels, because discrepancies can be detected between this act to extend the knee, places the right hand under the os calcis, and of walking and later passive strength testing. To assess and detect then lifts the leg while keeping the knee extended (Fig. 4c.2). weakness of the triceps surae muscles, which are innervated Because patients often describe their discomfort in different primarily through the S1 nerve root, the physician should ask locations in the extremity, the objectivity of the test results the patient to hop several times on the left foot, then on the are qualified. If the patient complains of radicular discomfort right foot, and note any discrepancies in the two abilities. The patient should be observed also while walking in the examining room. Extreme staggering from side to side and other bizarre gait patterns suggest symptom amplification. Patients with true herniated disks often have a gait pattern slightly antalgic on one side but with no bizarre abnormalities. Patient sitting The patient should next sit on the edge of the examining table so the physician can perform the knee and ankle reflex tests and determine the strength of the extensor hallucis longus muscle. This latter examination is critical in all patients complaining of back and leg pain because many have weakness of the extensor hallucis longus but not the tibialis anterior. Weakness of the extensor hallucis longus in a patient who complains of back and leg pain suggests involvement of the L5 nerve root. The extensor digitorum brevis muscle should be checked; however, some authors remain unconvinced that observation of this muscle has any diagnostic significance in patients with lumbar disk disease. Asymmetry is often observed in patients who have never had low back and/or leg pain.

Chapter 4c ● Physical examination 117 Figure 4c.2 Supine straight leg raise (SLR) test. For maximum Patrick’s test should then be performed bilaterally. In this test, accuracy in identifying sciatic tension, this test must be compared with the shear force applied across the sacroiliac joint helps detect the sitting SLR test. early abnormalities. Many patients with osteoarthritis of the hip complain of buttock pain rather than the classic groin discomfort, during the test, the limb should not be lifted any higher. At that causing the hip joint often to be overlooked because of the moment, plantar flexion of the ankle should be performed as a apparent back problem. Patients with abnormalities of the hip distracting test. Because plantar flexion of the ankle should not joint cannot tolerate Patrick’s test, however, because of the increase back pain, exacerbation of pain may suggest amplifica- discomfort when the limb is fully externally rotated into the tion of symptoms by the patient. Dorsal flexion, on the contrary, abducted position. While the patient is supine with the limbs should increase sciatic tension and pain (Fig 4c.3). extended, the physician should therefore gently rotate the lower extremity both internally and externally, a gradual rotation that The physician should perform the crossed SLR test also by reveals early irritability in the hip joint. If internal and external lifting the nonsymptomatic extremity as in the ipsilateral SLR rotations cause pain, it may arise from that area. Brown et al14 test. If the patient complains of discomfort radiating into the reported on the clinical signs that may be helpful to distinguish symptomatic extremity when the well extremity is lifted, this test between a hip disease and a spinal origin of pain: “the presence is positive, almost invariably indicating lumbar disk herniation. of a limp, groin pain, and limited internal rotation of the hips During both the SLR test and the crossed SLR test, the patient more often was associated with and predictive of a hip disorder must be allowed to state where the discomfort is occurring. than a spine disorder.” Specifically, asking the patient whether lifting the well extremity causes pain in the symptomatic extremity invalidates the test. The abdomen should be examined by palpating the four quad- rants to detect any intraabdominal masses. Abdominal lesions It is important to note that in patients with L4-L5 and L5-S1 may erode into the lumbosacral plexus and cause symptoms iden- disk herniations, the SLR test has very high sensitivity (95%) but tical to those of lumbar spinal stenosis or disk disease (Fig. 4c.4). lower specificity, whereas the cross SLR has much lower sensitiv- ity (25%) but significantly higher specificity (90%).20 The strength of the abdominal muscles should be assessed by having the patient flex the knees while keeping the feet flat on the table and then perform a sit-up. Patients who have extreme difficulty completing even one sit-up are theoretically excellent candidates for a vigorous rehabilitation program. In addition, the patient should be asked to hold the lower extremities 15 to 20 cm off the table. In general, a patient with an established herniated disk can easily perform this maneuver, so the primary value of this test is to assess the strength of the abdominal musculature rather than determine the likelihood of a disk herniation. With the patient supine, the motor strength of the iliopsoas, quadriceps, and hamstrings, along with Babinski’s reflexes and proprioception, should all be assessed. A sensory examination also should be performed and recorded. A study demonstrated significant elevations of warm, cool, and touch perception thresholds correlated with leg pain in patients with unilateral L5 or S1 nerve root pain. However, dermatomal quantitative sensory tests require some specific tools that are not part of the routine clinical equipment.54 Figure 4c.3 Dorsiflexion of the ankle during a straight leg raise test Patient on side increases pain. The supine patient is then asked to turn on one side and to raise and maintain the superior extremity against resistance by the physician (Fig. 4c. 5). In most patients, the gluteus medius is inner- vated primarily by L5, so patients with L5 radiculopathy often have weak abductors, as do patients with significant hip disease. The trochanter should be palpated to test for trochanteric bursitis. These same tests should be repeated with the patient lying on the opposite side. With the patient on one side, perianal sensation and but-tocks sensation also should be evaluated. All patients over the age of 40 and any patient suspected of a neurologic deficit should have a rectal examination. In males, anal sphincter tone and the size of the prostate may be assessed. Female patients with chronic back pain should have a pelvic examination by a gynecologist.

118 Chapter 4c ● Initial evaluation of the low back region AB Figure 4c.4 (A) CT of a calcified arthrosynovial cyst (circled) causing left nerve root entrapment. (B) The same pathology is less obvious on an MRI. Figure 4c.5 Gluteus medurs strength testing with the patient on the side and abducting against resistance.

Chapter 4c ● Additional investigations 119 Patient prone with precise description of nonsignificant abnormalities facili- tates the “medicalization” of low back pain,12 and duration of With the patient prone on the examining table, the lumbar disability is associated with its early increased use.47 spine, sacrum, and sacroiliac joints should then be reexamined for any localized tenderness. A reverse SLR maneuver can easily Patients’ perceptions, expectations, and demands play a major be accomplished by the physician simply by lifting both of role in the use of imaging modalities to diagnose low back pain. the patient’s lower extremities off the table, although quite A myth common among patients is that radiographs will show often just bending the knees in the prone position is enough the exact cause of their back pain,36 so they expect to have radi- to elicit pain in the L3 or L4 dermatome. The patient should ographs when seeing doctors for such complaints.43 They wish to next flex the knees 90 degrees so that the physician can observe have an x-ray examination ordered, moreover, and physicians’ internal and external rotation of the hips. In most patients, attitudes are often correlated to patient wishes.77 the amount of internal and external rotation is quite similar. Patients with femoral anteversion, however, have excessive It appears then that patient education is necessary, although internal rotation and limited external rotation and often physician education is perhaps even more acutely needed.74 experience discomfort in the low back area and buttocks Although many guidelines about diagnostic procedures in back while running. When the patient is prone, ankle jerks often are pain have been published in several countries, multiple studies easier to reexamine and compare; the absence of one or both show that most are not followed in the United States,27,56 Canada,8 reflexes should be noted. Finally, the patient should extend first Norway,77 and Spain.29 All those studies reveal that physicians, one lower extremity and then the other by using the gluteus mainly in primary care settings but also specialists, still order too maximus muscle. Increased low back discomfort during this many examinations that are of little use. maneuver suggests a more superficial myofascial source of the symptoms. Plain radiograph ADDITIONAL INVESTIGATIONS Plain radiographs have been the standard (and only widely available) imaging technique in assessment of back pain for After careful history taking and physical examination (and only decades. They show the bony structures precisely, displaying then), a number of technical examinations can be ordered based spondylolysis, spondylolisthesis, deformities, tumors, fractures, on the results. None of those examinations should be considered and degenerative changes such as disk narrowing, disk vacuum, as a screening tool, “to see how they come out.” A specificity of and traction osteophytes. The latter, however, appear to be a nor- low back pain is that in most cases a precise cause of nociceptor mal evolution of the spine and are very common in symptom-free cannot be precisely determined despite the increasing sophistica- middle-aged and aged subjects. Instability can be assessed on tion of investigations. dynamic (flexion/extension/lateral flexion) radiographs, but the relation of radiologic “instability” to back pain is subject to Specialized examinations should serve to confirm or pinpoint discussion.65 For these reasons plain films have very low specificity a suspected diagnosis, and the precision of each should be known. and therefore low diagnostic precision38 and make no difference to That precision can be determined by statistical measures of sen- the outcome for back pain,78 especially in elderly subjects.10,71 sitivity (the proportion of subjects with the disease in whom the examination is positive), the specificity (the proportion of sub- In the case of acute low back pain in a subject between 18 and jects without the disease in whom the examination is negative), 50 years of age, plain films are indicated only if there is a history the accuracy, and the predictive value. The two latter measures of trauma, malignant disease, or symptoms of infection. In the are not always available in all cases, and in the context of back case of neurologic symptoms, magnetic resonance imaging (MRI) pain the specificity of imaging is often poor due to a wide range (or computed tomography [CT] if it is unavailable) might be a bet- of abnormal images that are asymptomatic. With more sophisti- ter diagnostic tool. If no clinical improvement is observed after cated examinations, more asymptomatic abnormal images are 6 weeks, plain films may be taken to help exclude a diagnosis of found. In contrast to severe osteoarthritis of the hip or knee, tumor, infection, spondylolysis or olisthesis, and osteoarthritis of which does not affect everyone and is seldom asymptomatic, the hip, and along with simple laboratory tests will rule out sys- marked degenerative changes in the spine seem to affect nearly temic diseases.37 Some studies suggest, however, that in the all human beings with aging and are often asymptomatic. absence of red flags, radiographs should not be ordered even after 6 weeks of symptoms.41 In chronic low back pain, the same The patient should be told the reason for which an examina- pathologies should be ruled out, but preferably by MRI.10 tion is ordered and advised that it may show some meaningless “pathologic images” that are irrelevant to the present symptoms. Myelography Those incidental findings are usually nonsignificant and not what was suspected and researched. We all see patients coming with Until the advent of CT, myelography was the only examination multiple radiology reports where statements about “black disk,” that enabled physicians to assess spinal neural structures, the dural “bulging disk,” or “degenerative changes” have been strongly sac, and the roots. Myelography is still the only widely available underlined or highlighted by the patient (or sometimes the doctor). examination permitting a dynamic view of the dural sac during Those misconceptions can lead patients to further impressions of flexion and extension in the upright posture (Fig. 4c.6). Given the seriousness and prolonged disability. Early and complex imaging decrease of the dural sac diameter during extension, some cases of

120 Chapter 4c ● Initial evaluation of the low back region stenosis can be underestimated during examinations like CT or MRI that are performed in a supine position. Although upright MRI is becoming available, it is very expensive, uncommon, and constrained in patient positioning and acquisition time, making it inappropriate for this kind of assessment in stenotic patients. Upright myelography examination appears useful also in the diagnosis of position-related disk herniations35 and those in the lateral recess where MRI may underestimate root compres- sion in nearly 30% of cases.2 Indeed, some authors have demon- strated similar sensitivity and specificity in myelography and MRI.55 Myelography is an invasive procedure, however, and neuro- logic or infectious complications, although very rare, are possible. Combined with CT (myelo-CT), myelography still has a place in cases of strong clinical suspicion of stenosis or herniated disk not clearly demonstrated on other imaging modalities. It also enables the laboratory analysis of the cerebrospinal fluid to be performed to rule out a number of neurologic diseases. Figure 4c.6 Myelogram showing multiple level central degenerative Computed tomography stenosis (arrows). Myelogram remains the only widely available examination enabling dynamic and upright assessment. CT is the first examination to provide axial and three-dimensional representations of the spine and the first noninvasive examination to provide a view of spinal neural structures. When it appeared in the 1970s, it was a true revolution. It has now been widely replaced by MRI for the assessment of neural structures but still remains the best examination for the visualization of bony elements. It is also the only examination available for claustrophobic patients or for those with pacemakers or ferrous metallic implants. CT also offers more precise views of calcified disk protrusions.24 AB Figure 4c.7 (A and B) Spondylolysis and olisthesis are best investigated by computed tomography. In this case the pars defect is partially filled by Gill’s nodules (ossified fibrous tissue), which when associated with a disk bulge provoke a lateral stenosis.

Chapter 4c ● Additional investigations 121 CT shows more precisely the patterns of fractures in trauma which presented at least one bulging disk.39 With MRI, degener- cases and investigates pars fracture in spondylolysis or olisthesis ative intervertebral disk disease is present in one third of subjects (Fig. 4c.7). In the case of spinal stenosis, if MRI allows a better between 20 and 39, over half of those between 40 and 59, and in view of neural elements, CT is still invaluable to investigate the nearly all subjects over that age.11 Apparently, a normal physio- osseous participation in the stenotic process. We believe that it logic evolution of the decrease of disk hydrophilic properties, dark complements MRI before surgical treatment of lumbar stenosis. or black disks, appear in almost everyone. These findings under- Spiraled helical CT allows a three-dimensional view of long line that to avoid misunderstandings by patients, MRI results spinal segments and as such may be very interesting for the accu- must be interpreted with great care and meticulously related to rate description of deformities. clinical presentation. Even in the presence of symptoms, the cor- relation between the severity of clinical findings and MR images Magnetic resonance imaging of mild to moderate compression due to bulging or stenosis is poor.4 MRI has become the standard investigation tool for spinal disor- ders. The precision of this examination handicaps its specificity, Keeping these limitations in mind, MRI is nevertheless the best however, because it demonstrates a high frequency of clinically tool to investigate compromise of neural elements of the spine. irrelevant abnormal images without associated symptoms. Some In spinal stenosis it is especially useful in determining the extent studies have shown a prevalence of 28% of disk herniations, at of the narrow canal. In presence of a suspicion of neural compres- an average age of 42, in asymptomatic subjects,11,39 up to 52% of sion, the addition of MR-myelography, realized through specific acquisition sequences, complements the results of the standard MRI in many cases (Fig. 4c. 8,9).26 Figure 4c.8 Voluminous extruded disk herniation provoking a cauda Figure 4c.9 Magnetic resonance image of a lytic spondylolisthesis equine syndrome. In this case magnetic resonance imaging is the showing root entrapment in the foramen. The root (A) is hampered by examination of choice. The patient had a full recovery after surgery. the disk bulge in the foramen (B) consecutive to the sliding and flattening of the disk.

122 Chapter 4c ● Initial evaluation of the low back region Because it is usually performed in the supine position, MRI have proposed ultrasonic imaging combined with pain provoca- may underestimate images of compression in position-related tion by vibrations to diagnose internal annular tears,79 but this stenosis or sciatica, as is the case with neurogenic claudication. technique has not gained widespread acceptance. Investigation Devices enabling axial compression during supine MRI (or CT) of nerve roots and facets has been abandoned due to the lack of appear to add useful information about the decrease of the accuracy.51 Those examinations do not play a major role in spinal spinal canal diameter that appears during upright weight-bearing imaging. positions76 and also to enable more precise surgical strategies to be performed.32 MRI is highly specific and sensitive also in the Diskography research of malignant and infectious spinal diseases, warranting the use of gadolinium-enhanced MRI in acute low back pain when one Provocative diskography, which aims at back pain reproduction, of those pathologies is suspected.30 has been a controversial subject for many years. It has been con- sidered by some authors to be the best indicator of discogenic The results in MRI investigation of back pain are more subject pain and has been widely used to confirm surgical indications of to caution. An example is the high intensity zone, the presence fusion and, more recently, disk replacement. Even after positive of which has appeared to show much promise as a marker of diskography, however, fusion results remain unpredictable.75 discogenic low back pain. The high intensity zone is a high T2 Furthermore, the frequency of positive responses to diskography signal in the posterior and/or posterolateral annulus that seems among asymptomatic subjects challenges the value of this examina- to increase during axial loading.59 Some authors have found a tion as a predictor of clinically relevant discogenic pathology.16,18 high correlation of this finding with pain and annular penetration Although diskography is indeed a good indicator of annular of the dye during diskography, which they believe demonstrates tears, the latter do not appear to predict a clinically relevant a very high positive predictive value.1,60 Other authors, however, spinal pathology.16 Specificity of diskography appears low,17 and have shown a high prevalence of high intensity zone in asymp- pain intensity during injection is influenced strongly by the tomatic subjects,15 whose reaction to diskography is similar to patient’s psychologic factors and compensation claims.16 In any that of symptomatic patients.20 The sensitivity of the sign is low,58 case, diskography has no place in the initial assessment of low back and although it seems that the high intensity zone may show an troubles. annular fissure, that fissure is not a reliable sign of painful disk disease. In patients without active symptoms, furthermore, annular Electromyography disruption is a weaker predictor of future low back pain than psychologic distress.19 Electromyography may be useful in specifying the level of symp- tomatic compression and ruling out peripheral neuropathies Radionuclide bone scan (diabetic, ethylic, or other). One must bear in mind that elec- tromyography shows abnormal signals only several weeks after Radionuclide bone scan (isotopic) is a highly sensitive but the occurrence of a nerve compression. Although interesting as poorly specific examination. Of the different radionuclides that an adjunct examination, electromyography is not an essential can be used, technetium-99m is the most common in spinal indi- tool in the initial assessment of spinal troubles. cations because it is highly sensitive for malignant diseases and infections. Bone scans using markers such as gallium or marked Mechanical testing leucocytes show better specificity for infections. The inability to correlate low back pain to anatomic findings and Nearly 40% of subjects with spinal metastasis and normal plain the difficulties in quantifying pain have directed much effort films have a positive bone scan.50 The test might help also to deter- toward measurement of spinal performance through the assess- mine whether a vertebral or pelvic fracture is recent or old. ment of function across various dimensions such as flexibility, strength, speed, endurance, and coordination. Goniometers and Single photon emission CT has been suggested as useful for isokinetic and isoinertial dynamometric devices are currently identifying patients with facet joint disease more likely to benefit used. Isoinertial testing seems to be the most physiologic and from facet injections.23 Single photon emission CT also reveals clinically relevant approach. Useful for prescribing muscle- many abnormalities not detected on a standard radiograph,57 but strengthening therapy precisely, it enables the physician to follow here again one might wonder about the clinical relevance of those up on the patient’s progress and can also be used to assess the effi- findings. cacy of diverse treatments.44,46,68 In certain pathologies like spinal stenosis, specific patterns of motion have been demonstrated,69 Whereas either the planar bone scan or single photon emis- and early decrease of spinal function has been shown in subjects sion CT reveals areas of increased bone turnover, these tests lack with Parkinson disease.13 The use of neural network technique the specificity necessary to determine the true nature of the analysis of motion patterns has enabled researchers satisfactorily “lesion” and serve only as indicators for further studies in accor- to assign back pain patients to pathologic categories based on the dance with the clinical presentation. Quebec Task Force classification.7 These tests can also provide insight into the maximum effort exerted by the subjects62,66 but Ultrasonography Ultrasonograms may be useful in cases of paraspinal soft tissue infections or tumors or to rule out other sources of lumbar pain, such as urinary tract calculus or kidney diseases. Some studies

Chapter 4c ● References 123 despite the hopes of their proponents are by no means back pain Evidence-based medicine principles apply to diagnostic investi- “lie detectors.” gations, but there are no screening tests for back pathologies. The poor specificity of the most common imaging techniques is The measure of flexibility is of limited value in the assessment inversely proportional to the frequency of their use. Radiographs of the spine,70 and the current American Medical Association and now MRI, which seem to be used almost as routine investiga- guidelines for evaluating disability, heavily based on spinal range tions in low back pain patients, provide a huge quantity of clini- of motion, can lead to irrelevant results.45 More elaborate proto- cally irrelevant information. In a world in which health care cols, based on more complex analysis of kinematic profiles, appear resources are decreasing while the population ages and increasing to be much more promising.25 technology costs demand further funding, physicians will be held accountable for unjustified practice costs. Patients should be edu- Other diagnostic studies cated and alerted that technology will not invariably uncover the precise reason of their pain, but physicians too require education, Laboratory evaluation should be recommended for patients as the failed implementation of many guidelines painfully shows. who are not responding to treatment or who have severe pain. Although many of these tests are indicated in specific situations, REFERENCES a useful screening evaluation for patients with persistent symp- toms should include a complete blood count, sedimentation 1. 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In JN Weinstein, SW Wiesel, eds: The lumbar 44. Klein RG, Eek BC: Low-energy laser treatment and exercise for chronic low back spine. Philadelphia, 1996, WB Saunders. pain: double-blind controlled trial. Arch Phys Med Rehabil 71:34-37, 1990. 71. Tress BM, Hare WS: CT of the spine: are plain spine radiographs necessary? Clin Radiol 45. Lowery WD Jr, Horn TJ, Boden SD, Wiesel SW: Impairment evaluation based on spinal 41:317-320, 1990. range of motion in normal subjects. J Spinal Disord 5:398-402, 1992. 72. Verbeek J, Sengers MJ, Riemens L, Haafkens J: Patient expectations of treatment 46. Magnusson ML, Bishop JB, Hasselquist L, Spratt KF, Szpalski M, Pope MH: Range for back pain: a systematic review of qualitative and quantitative studies. Spine 29: of motion and motion patterns in patients with low back pain before and after 2309-2318, 2004. rehabilitation. Spine 23(23):2631-2639, 1998. 73. Waddell G, McCulloch JA, Kummel E, Venner RM: Nonorganic physical signs in low 47. 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4dC H A P T E R TREATMENT MODELS Treatment Options Two treatment models are commonly used in treating back pain: the medical model and the biopsychosocial model. Modern Margareta Nordin, Federico Balagué, and Christine Cedraschi medicine uses the classic scheme, which implies that an interac- tion between the patient and an exposure leads to an illness More than 17 guidelines drawn from large evidence-based complex.99 This model works well in dealing with SLBP. The pro- systematic literature reviews have been published in different cedures are to countries on low back pain (LBP),8,79,96 a topic that the World 1. Recognize patterns of symptoms and signs by history and Health Organization included in their report, the Bone and Joint Decade 2000-2010.38,59,98 examination; 2. Identify underlying injury or disease by investigation and LBP remains a common affliction that is debilitating for the patient and expensive for the working individual and for diagnosis; society.31,70 This chapter gives an overview of treatment modali- 3. Treat underlying injury or disease by specific intervention; ties for returning an individual to work during the course of 4. Expect the patient to recover. acute to chronic LBP. The focus is on LBP that is nonspecific, where causality cannot be established and which is treated by Preferably applied to NSLBP, the biopsychosocial model identi- a structured evidence-based approach to prevent disability and fies factors associated with delayed recovery for return to activity chronicity. and, most often, return to work. The model calls for identification of symptoms and signs outside the traditional medical field SPECIFIC AND NONSPECIFIC LBP such as beliefs, high perception of disability, kinesophobia, depression, stress, job dissatisfaction, anxiety, somatization, or The classification for pain in the lumbar spine used by clinicians lack of control.22,94 is “specific” or “nonspecific,” depending on which of more than 60 diagnoses applies. These contributing factors are treated with nontraditional medical approaches such as cognitive behavioral therapy (CBT) Specific low back pain or ergonomic or occupational intervention. The biopsychosocial model in occupational health care helps to The common feature for specific low back pain (SLBP), the diagno- 1. Recognize the nonspecific nature of the back pain; sis in up to 2% of all early back pain cases, is a causal link between 2. Identify underlying psychosocial and/or environmental a structural pathology and the described experience of the patient (see Chapter 4c). SLBP may result from systemic disease, infection, factors; injury, trauma, cauda equine, or structural deformity. Additionally, 3. Treat these factors with appropriate interventions; nerve root pain, which occurs in about 5% of the individuals 4. Empower the patient to assume responsibility for managing a seeking care early, includes diagnoses such as a disk prolapse or spinal stenosis. These conditions are treated with or without condition with possibly frequent recurrence. surgery and should be referred to a specialist for determination of care.6,8,57 The first occupational health guidelines for the management of LBP at work were published in 2001 (see also www.facoccmed. Nonspecific low back pain ac.uk).96 These guidelines are based on an extensive systematic review of the scientific literature primarily in terms of occupational Nonspecific low back pain (NSLBP), which afflicts 85-90% of all settings or outcomes. individuals seeking care, is a diagnosis of exclusion: No precise structure is identified as the cause. NSLBP is attributable to PATIENT EXPECTATIONS common diagnoses such as lumbago, myofascial syndromes, muscle spasms, mechanical LBP, back sprain, and back strain. A patient approaches a physician with expectations and precon- These conditions all include pain in the lumbar region that may or ceptions. The patient expects diagnostic explanation, pain relief, may not radiate to one or both thighs but not below the knee(s). referral for treatment, instructions for coping with pain and The following International Classification of Diseases diagnostic disability, and, in an occupational environment, help with sickness codes are suggested to best represent NSLBP: lumbago (724.2) and certification or light duty assignment. Some patients expect sprains of the lumbosacral region (846.0-3/8-9, 847.2-3).24 imaging or special tests and specific medication. In one cross-sec- tional study (n = 1942), for example, 77% of the responders believed that if back pain exists, a wrong movement could lead to a serious problem. Forty percent believed also that radiographs and imaging could always identify the cause of back pain.40 It takes time to explain inappropriate concepts and expectations. The first encounter addresses such misconceptions, whereas at subsequent visits the important concepts for recovery are dis- cussed and reinforced.69,91 Evidence-based information educates the patient that selective treatments may take time; some treat- ments may pose higher risks, and the effects of new treatments

126 Chapter 4d ● Treatment options are not entirely known. The patient and clinician discuss the pro- on exercises and NSLBP, the authors concluded that “exercise posed treatment and the prospect of harm when work is resumed therapy is as effective as either no treatment or other conservative and agree on a regimen including compliance and return to work. treatments” in 11 trials involving 1192 adults.1,45,88 Patient education about treatment choice and expected outcome is a key factor for success.49,97 A series of five to six manipulations in the acute stage of NSLBP reduces pain and disability for up to almost 3 weeks.4,8,14,33 NATURAL HISTORY AND RECURRENCE Alternatively, the patient may have a short course in pain man- OF NSLBP agement involving five to six encounters with a therapist trained in the biopsychosocial approach.61 Acute NSLBP has a favorable prognosis. Some authors argue that NSLBP is a lifetime disease if recovery has not occurred In a comparison of manipulation and pain management during the first 3 months,10,84,92 as is true for a large subgroup of in patients with acute NSLBP, the outcomes at 3 months and individuals.48 Von Korff et al93 found that 20% of the U.S. pop- 12 months were almost identical (difference 0 [95% confidence ulation suffers from chronic LBP each year and that about 30% interval (CI), -1.3-1.4]), with a decrease in disability score of of them suffer chronic pain over their lifetimes. about 8.8/24 points.44 With the patient maintaining tolerable activity, manipulations and pain management in acute NSLBP Studies focusing on the natural history of LBP report that are superior to all passive modalities (mobilization, diathermy, 80% of patients who consult a health care provider for acute massage, heat) over the long term.21,33 Continued passive long- NSLBP can expect to resume normal activities within 4 to term treatment of NSLBP is harmful because it precludes patient 6 weeks. By 12 weeks, the rate of recovery rises to almost 90%. involvement, increases fear that the condition is serious, Compared with approximately 35% to 40% of patients with decreases cardiovascular conditioning, and reinforces the role SLBP, 10% or fewer of NSLBP patients experience chronic pain of sick person.94 and work incapacity.1,11,70 For the employee seeking care, the message is sometimes dif- The recurrence rate in NSLBP varies considerably from 5% to ficult to understand, particularly if the injury or back pain started 70%, with up to 2 years follow-up in studies of both general and at work. “Why should I go back to work, where I was injured, if specific occupational populations.18,92 Recurrence or episode rate it may hurt my back?” he or she asks. This legitimate question is difficult to estimate, however, because the definition of an needs to be answered in relation to the type of job involved and episode is not standardized in different studies.29 We diagnose the availability of modified work for a limited period if neces- recurrent NSLBP when the employee has returned to regular sary. The occupational health care provider is best placed work pain free for at least 8 weeks since the previous episode.71 to answer this question and to adapt the employee’s duties if necessary. DURATION OF PAIN AND TREATMENT GOALS Self-care for acute NSLBP The following definitions of LBP and duration since onset are used and well accepted: The duration of acute NSLBP is 0-4 weeks Self-care implies that the NSLBP patient can control symptoms and that of subacute NSLBP is 4-12 weeks.1,8,33 Although episode and engage in behaviors necessary to reduce or alleviate them. definition is not standardized, intermittent or recurrent NSLBP Playing an active role in recovery, the patient decides what is diagnosed when the patient is pain free or almost pain free behaviors are tolerable. The message to remain as active as pos- between the bouts of pain.1 Chronic NSLBP is defined as a dura- sible cannot be overemphasized.1,88 Self-care techniques include tion of pain longer than 12 weeks.1,8,17,33 (but are not limited to) stretching and/or walking or using heat and/or ice or relaxation techniques72 when convenient for short- The most important goal for acute LBP is a continuum of occu- term relief. pational care and identification of factors to prevent chronicity during the first 3 months after the patient seeks help. Management Written evidence-based information is helpful to reinforce in occupational medicine can make a difference by providing the good prognosis of NSLBP, explaining the biopsychosocial fac- regular follow-up and using a multidisciplinary approach to rein- tors influencing recovery and offering instructions for self-care.16 force return to work with temporary job accommodations or, in Company-specific information may have a better impact than a some cases, job change. generic pamphlet.46,75 ACUTE NSLBP AND EVIDENCE In summary, systematic literature reviews, randomized con- FOR TREATMENT trolled trials, and meta-analysis of acute NSLBP show that self- care in the form of maintained activity, education, and Because acute NSLBP is largely self-limiting, minimal or no med- medication as needed is as effective as manipulation or a short ical interventions are recommended for most patients.1,26,33,67,88,95 course of pain management based on the biopsychosocial The most important message is for the patient to keep as active model. Bed rest and passive treatment should be avoided. If as tolerable without bed rest.1,33,67,73,74,88 patients demand treatment, it is prudent to ask about their expectations and goals, educate them, and reinforce the positive Specific exercises are not needed and may also have a nega- prognosis. The natural history of acute NSLBP measured as tive effect. In two systematic reviews and a recent meta-analysis return to work is altered only marginally by prescribed treatment at this early stage, but together with self-care it provides short- term relief from pain. Patients should be followed until they resume work.

Chapter 4d ● Interventions for subacute NSLBP 127 INTERVENTIONS FOR SUBACUTE NSLBP In one study from a primary care cohort (n = 800) over 5 years, not recognizing psychosocial issues early on has been shown The interval of 4-12 weeks in the management of NSLBP has to account for an increase of 10 consultations per year per been called “the window of opportunity.” The occupational patient.52 health care professional can become instrumental in preventing work disability and recommending alternative and more inten- Blue flags sive regimens of evidence-based treatment. A clinical reevalua- tion at 4 weeks includes a careful orthopedic and neurologic In occupational health care it is also helpful to recognize so-called examination along with imaging and other diagnostics if war- “blue flags” that are related to possible work problems. Initially ranted to exclude any ongoing process in the spine.8,33 If the proposed by Main and coworkers,7,65,66 blue flags represent occu- diagnosis remains NSLBP, screening for psychosocial factors is pationally related predisposing factors for delayed recovery and warranted. return to work. Blue flags include factors such as fear of losing one’s job, monotony at work, lack of job satisfaction, and poor Yellow flags relationships with peers and supervisors. Occupational health care professionals are particularly well placed to address these “Yellow flags”56 indicate psychosocial barriers to recovery and pre- issues. Appropriate intervention such as CBT aims to strengthen dict poor outcomes related to occupational health care because the employee’s coping skills and problem solving. In collaboration the patient does not return to any kind of work.55 Yellow flags are with the occupational physician, a discussion with supervisors or employee misconceptions (that back pain is harmful or can be a workplace visit can occur early in the course of back pain to severely disabling), avoidance of movement or activity due to prevent chronicity. An active approach combining patient partic- fear of pain, tendency toward depression, withdrawal from social ipation with involvement by the health care provider, the man- interaction, or expectation of continued passive treatment rather agement, and the union is beneficial.60,62,81 than belief that active participation will help.55,61 Management of NSLBP Six open-ended questions are helpful for revealing yellow flags: The management of subacute NSLBP treatment should proceed 1. Have you had time off work in the past with back pain? in a stepwise fashion from least to the most invasive treatment 2. What do you understand to be the cause of your back (Fig. 4d.1). There is weak to moderate evidence in randomized controlled trials for efficacy of a treatment regimen including pain? exercise, behavioral therapy, and ergonomic intervention.33,70 3. What do you expect will help you? The employee must be convinced to participate actively to pre- 4. How is your employer responding to your back pain? Your vent long-term chronicity and disability. Meaningful outcomes for the patient that need to be discussed are those of taking control of coworkers? Your family? 5. What are you doing to cope with your back pain? 6. Do you believe you will return to work? When? 100 Work disability in % • Convey optimism • Convey optimism • Exercise • Stay active • Exercise • Aggressive pain management • Pain medication • Pain medication • Cognitive behavoral treatment 50 • Self care techniques • Psychological evaluation • Multidisciplinary conditioning • Follow-up and possible cognitive program with focus on return • Pamphlet/information behavoral treatment to work • Work conditioning program • Workplace intervention • Ergonomic and/or • Surgery (?) occupational intervention 0 1 month 3 months >6 months Chronic Acute Subacute Early chronic Figure 4d.1 Suggested management of occupational nonspecific low back pain.

128 Chapter 4d ● Treatment options the condition; feeling better; resuming activities, including work; Combination therapy in occupational and avoiding recurrences. settings Because compliance with regimens requires the patient’s active Three studies in occupational settings have found that a behav- participation, management of subacute NSLBP is demanding. iorally oriented graded-activity exercise program provides mod- Compliance rates for different regimens have been reported to erate to excellent reduction of days lost at work. This type of vary from 13% to 85%,2,61 and a patient’s decision to adhere to program has been compared to usual care in the Netherlands a treatment regimen is complex.50 Patients may prefer passive and in Sweden.60,81,86 These studies had highly structured inter- treatment that may delay the course of recovery.83 One study has ventions with an unambiguous primary goal of returning the shown, for example, that patient compliance with video watch- patient to work. ing for back education (70-80%) in a physical therapy practice was significantly higher than compliance with a more demanding A behaviorally oriented graded-activity exercise program exercise regimen (40-50%).2 Linton and Andersson61 indicated includes the following components: an adherence rate of 53% and 72% for six and four CBT sessions, 1. The occupational or treating physicians advise workers on respectively. ergonomics, prevention, and return to work schedules; Adherence appears to be influenced by both the type of treat- 2. The clinicians also advise and communicate with interested par- ment and its frequency. The stepwise active approach includes an exercise regimen or a CBT program as a single intervention or a ties such as health care providers and workplace representatives; combination of the two as a bimodal treatment if no recovery 3. The programs use gradually progressive exercises adapted to occurs. patient needs; Exercise regimens 4. The clinical team is trained, and all caregivers provide the The message here is for the patient to “start moving” with or same message to the patient to avoid ambiguity; without help from a coach. There are many different types of 5. There is ample communication and discussion with the patient; exercise regimens for LBP, each with its own proponents. 6. An ergonomic intervention such as a workplace visit or a dis- Exercise programs evaluated in randomized controlled trials include the McKenzie regimen, walking programs, Williams flex- cussion with the occupational physician may be included.60,62 ion exercises, endurance-strength-stabilization training, and other less frequently described regimens.23,27,43,47,54 Different types The studies showed significant reduction in days of work of exercises appear to be equally effective.1,87 loss. Lindstrom et al,60 for example, showed an average return to work in the intervention group at 10 weeks (standard deviation, A recent meta-analysis of five exercise studies involving 12.7) and in the control group at 15.1 weeks (standard deviation, about 800 patients resulted in pooled weighted difference 15.6). Staal et al80 showed an effect on work loss days (HR 1,9; decrease in pain of about two points (1.89 [95% CI, -1.13 to CI, 1.2-3.2) at 50 days after randomization in favor of the 4.91) on a scale of 100. Pooling four trials demonstrated an graded-activity program. However, the results were not signifi- improvement of 1.07 (95% CI, -3.18 to 5.32) points on a scale of cant in early follow-up less than 50 days after treatment for 100 for perceived functional outcomes.45 The authors concluded the two interventions (an exercise program and a graded operant that the evidence is insufficient to refute or support the effective- conditioning program). ness of regimens involving exercise alone without a behavioral component. One randomized controlled trial in an occupational setting in the Netherlands added problem-solving therapy conducted by Cognitive behavioral therapy a trained therapist to a behaviorally oriented graded-activity exercise program for patients with subacute and chronic NSLBP. CBT interventions include creative visualization, imagery, pro- The combination group showed significantly favorable results, gressive muscle relaxation, problem solving, and other techniques. including fewer work loss days and fewer patients receiving The clinician uses the components in various combinations to disability pensions 1 year after the intervention.86 have the patient understand, accept, and take control of the back pain. Moderate to strong evidence indicates that CBT should be In all studies, self-reported pain and function were affected used early if biopsychosocial signs or symptoms are present, and marginally.60,80,86 Usually measured by a pain score or visual ana- strong evidence exists for using CBT in patients with chronic log scale, pain itself appeared not to be a major determinant for NSLBP.33,87,96 The European Guidelines 2005 stated, “We recom- return to work. Possibly the highly structured positive environment mend cognitive-behavioural treatment for patients with chronic in an occupational setting provides a better venue for problem LBP,” and summarized as follows: solving, educating the patient, and monitoring progress. Ergonomic intervention There is strong evidence that behavioural treatment is more Using the Sherbrooke model of occupational/ergonomic interven- effective for pain, functional status, and behavioural outcomes tion and clinical rehabilitation, Loisel et al62 found that a consulta- than placebo/no treatment/waiting list control. There is strong tion with an occupational physician or a low-cost ergonomic evidence that a graded activity programme using a behavioural intervention contributed the most to the success of return to work. approach is more effective than traditional care for returning In a follow-up study of cost effectiveness 6.4 years later, the same patients to work, and finally there is strong evidence that there authors found that the Sherbrooke model yielded the highest sav- is no difference in effectiveness between the various types of ings in work loss days compared with standard care or rehabilitation behavioural therapy.33 alone.64 The authors assessed participatory ergonomics in workers

Chapter 4d ● Medication 129 suffering from subacute LBP (>6 weeks of work disability). meta-analysis, Cherkin et al compared sham manipulation, trac- Performed 6 months after the ergonomic intervention, the assess- tion, corset, bed rest, home care, topical gel, diathermy, massage, ment included all parties: management, union, and afflicted worker. general practitioner care, analgesics, physical therapy, exercises, About half of the recommended ergonomic solutions were imple- back training, no treatment, or some combination thereof. mented with a substantial agreement among all respondents.63 They found no evidence that spinal manipulation is substantially more or less effective than other conventional therapies for chronic The Cochrane review of multidisciplinary biopsychosocial NSLBP. The expected gain in pain reduction is 4-5 points (ranging rehabilitation concluded, “There is moderate evidence showing from -4 to 12) on a 100-mm visual analog scale for pain of long- that multidisciplinary rehabilitation for subacute LBP is effective term duration and somewhat less for self-reported disability. These and that a work site visit increases the effectiveness.”53 These measures were reported for both the short and the long term.25 findings must be interpreted with caution, however, because the few studies reviewed contained methodologic flaws and need to A UCLA study (n = 681) included about 50% patients with be confirmed. Based on several studies of patients with chronic chronic NSLBP in a managed care health organization. The back pain, the European Guidelines 2005 recommend an occu- patients were randomized to chiropractic, medical, or physiother- pational intervention.33 apy care, and at a 6-month follow-up the results were comparable.51 Chiropractic care in combination with physical modalities or phys- MULTIMODAL PROGRAMS FOR CHRONIC LBP ical therapy modalities provided in combination with medical care did not produce clinically significant improvements in outcome.58 Two recent reviews and one systematic Cochrane review of chronic NSLBP showed the importance of multimodal active The European Guidelines 200533 recommend a short course programs.9,10,19,39,42 The Cochrane review covered 18 trials, of spinal manipulation/mobilization as a treatment option for including 1964 chronic NSLBP patients (Fig 4d.2).53,87 The com- chronic LBP. They also summarize the evidence for medication parison included treatment such as back training, exercise only, use as follows. education, standard care, assessment by specialist with or with- out a nurse and/or advisement (oral and printed), waiting lists, MEDICATION and other factors. Nonsteroidal antiinflammatory drugs Like the European Guidelines 2005, the review concluded, (NSAIDs) “There is strong evidence that intensive multidisciplinary biopsy- chosocial rehabilitation for chronic NSLBP with a functional The usefulness of nonsteroidal antiinflammatory drugs (NSAIDs) restoration approach reduces pain when compared with in- was reviewed systematically by van Tulder et al,89 who highlighted patient or out-patient nonmultidisciplinary treatments and mod- the methodologic problems they encountered. Most of the pub- erate evidence when these programs are compared to usual care. lished trials reported on acute LBP. In comparison with placebo, There is contradictory evidence regarding global vocational out- the authors found “conflicting evidence” that NSAIDs provided comes.”42 The authors cautioned about the lack of definition better pain relief, but patients on NSAIDs exhibited significantly concerning content, duration, and intensity of the programs but less use of analgesics. There were no significant differences in found that those longer than 100 hours of therapy with a focus terms of side effects. In the same review, “conflicting results” were on functional restoration seem to be more effective than less found among studies comparing NSAIDs with paracetamol. intensive programs or nonmultidisciplinary control groups. Included in the same systematic review were six studies comparing The review indicated significant and favorable results for pain NSAIDs with narcotic analgesics or muscle relaxants. The authors ratings, functional status, employment status, and sick leave up found “moderate evidence” that NSAIDs are not more effective to 60 months. than other drugs. van Tulder et al89 highlighted the impossibility of making any statement about the relative effectiveness of differ- MANIPULATION ent NSAID types because no studies comparing the same two drugs for acute or chronic LBP were available. Manipulation has been evaluated extensively for chronic LBP Muscle relaxants and studied less in the subacute phase. A recent pragmatic ran- domized trial, however, included 181 general practices in the Benzodiazepine and nonbenzodiazepine muscle relaxants, either United Kingdom with 1334 patients, most of whom had suba- isolated or combined with other drugs, have been extensively cute NSLBP. Patients were randomized to groups of standard investigated in LBP. A systematic review of this literature was best care or manipulation, each with or without exercise, and fol- published by van Tulder et al.90 Limited evidence from one study lowed for 1 year.85 Results on the Roland Morris disability ques- favored diazepam (an intramuscular injection followed by 5 days tionnaire76-78 improved with a mean of 3.3 (standard deviation, 4.5) of oral treatment) versus placebo. The authors found strong and 3.5 (standard deviation, 4.7) points out of a total score of evidence both that oral nonbenzodiazepines are more effective 10 points at 3 and 12 months, respectively. A score change of than placebo for short-term pain relief and that both types of 20% is deemed clinically significant.10 The difference between muscle relaxants are associated significantly more than placebo the groups was nonsignificant. with central nervous system side effects. Because the number of high-quality studies comparing different muscle relaxants is Manipulation for chronic NSLBP was reviewed extensively by Assendelft et al,4 Bronfort and Bouter,13 and Cherkin et al.25 In a

130 Chapter 4d ● Treatment options Trial Time since Pain Functional Employment Days on characteristics treatment record status status sickness leave Intensive (>100h) daily MBPSR with functional restorative: Alsants 1994* 3 months v >100h inpatient 12 months rehabilitation Bendix 1995:1* 4 months v<30h outpatient 12 months 24 months rehabilitation 60 months Bendix 1990 4 months v usual care 24 months 60 months Michel 1994* 4 months v usual care 12 months 24 months Less intensive (<30h) once or twice daily outpatient MBPSR: Bazier 1997 At treatment v outpatient completion rehabilitation 6 months Bendix 1995:2* 12 months v<10h outpatient 24 months rehabilitation 30 months Nichols 1991* 6 months v<30h outpatient 12 months rehabilitation Nichols 1992* 6 months v<30h outpatient rehabilitation 3 months 12 months Martapea 1989:2 30 months v usual care 54 months Other types of MBPSR: Martapea 1989:1 3 months Inpatient MBPSR 12 months >108h (no func- 30 months tional restoration) 54 months v usual care At treatment Juckel 1990 completion Sμ type MBPSR v waiting list Uritias 1989* 12 months Individualized inpatient MBPSR v usual care –2 –1 0 1 2 –2 –1 0 1 2 0.1 1 10 –2 –1 0 1 2 Standardized Standardized Relative Standardized mean difference mean difference risk mean difference Figure 4d.2 Treatment effect sizes for 12 randomized comparisons of multidisciplinary biopsychosocial rehabilitation and a control condition. Bars represent standardized mean differences and 95% confidence intervals for comparison of intervention and control groups, except for employment status, where bars represent relative risks. Treatment effect sizes entirely to the left of the vertical line indicate statistically significant differences in favor of the intervention. *, High quality trial; I1, intervention 1 testing more than one multidisciplinary intervention; I2, intervention 2 testing more than one multidisciplinary intervention; MBSPR, multidisciplinary biopsychosocial rehabilitation.

Chapter 4d ● Surgery 131 rather limited, it seems very difficult to make general recommen- spondylolysis and back pain.39 Three randomized trials have since dations in this area. There is strong evidence that combining shown that long-term benefits for surgery over 2 years is compara- tizanidine plus paracetamol or tizanidine plus NSAIDs is more ble with those of nonsurgical treatments.15,35,37 In a large random- effective for short-term pain relief than placebo plus paracetamol ized controlled study, Fritzell et al36,37 compared fusion with usual or plus NSAIDs. conservative care in patients (n = 294) with one- or two-level disk degeneration and pain duration of at least 1 year. The surgical Two high-quality trials offer strong evidence that temazepam group had a greater improvement in pain relief, function, depres- 50 mg 3 times a day is more effective than placebo for short-term sive symptoms, and return to work at 1-year follow-up compared pain relief and overall improvement. When the literature review with those who had common conservative treatment prescribed by was published, however, this drug was available only in some a physician. At 2-years follow-up, the difference between the European countries and Mexico. Among the nonbenzodiazepines, groups had diminished, suggesting that the results of fusion are there is moderate evidence that flupirtine and tolperisone are more intermediary rather than long term. The heterogeneous therapy in effective than placebo for short-term improvement.90 the nonsurgical treatment may also have contributed to a less favorable result in the nonsurgical group. The nonsurgical group Opioids received a variety of treatments according to individual physician preferences such as acupuncture, physical therapy, injections, Breckenridge and Clark12 and Fillingim et al35 independently electrical stimulation, and CBT. The study did not have blinded showed that the use of opioids in chronic LBP patients was not evaluators. predicted by pain intensity. Therefore, the factors influencing health care providers to prescribe opioids probably deserve more In a smaller randomized trial, 64 patients aged 25-60 years research. with NSLBP lasting longer than 1 year and evidence of disk degeneration at L4-L5 and/or L5-S1 at radiographic examination Antidepressants were randomized to either lumbar fusion with posterior transpedicular screws and postoperative physiotherapy or cogni- The efficacy of antidepressants in chronic LBP was systematically tive intervention and exercises.15 The cognitive intervention con- reviewed by Staiger et al.82 Based on the seven studies reviewed, sisted of a lecture to help patients understand that ordinary the authors concluded that tricyclic and tetracyclic antidepres- physical activity would not harm the disk and a recommenda- sants can produce moderate symptom reductions. Inhibition of tion to use the back and bend it. This was reinforced by three norepinephrine reuptake seems important for the analgesic effect. daily physical exercise sessions for 3 weeks. The main outcome Benefits appear to be independent of a patient’s depression. measure was the Oswestry Disability Index. Selective serotonin reuptake inhibitors were evaluated in three studies that failed to show any analgesic effect. It remains unclear At a 1-year follow-up visit to 97% of the patients, the whether these drugs affect functional status. Oswestry Disability Index was significantly reduced from 41/100 to 26/100 points after surgery, compared with 42/100 to Corticosteroids 30/100 points after cognitive intervention and exercises. The mean difference between the groups of 2.3 points (-6.7 to 11.4; p = 0.33) In their review, Atlas and Nardin5 stated that evidence support- was not significant. Improvements in back pain, use of analgesics, ing the use of oral corticosteroids is lacking. Because these drugs emotional distress, life satisfaction, and return to work were not have potential significant side effects, the authors therefore advised different. Fear-avoidance beliefs and fingertip-floor distance were against their use in patients with chronic pain. reduced more after nonoperative treatment, and lower limb pain was reduced more after surgery. According to an independent SURGERY observer, the success rate was 70% after surgery and 76% after cognitive intervention and exercises. The early complication rate Chronic NSLBP would imply LBP without sciatica in patients in the surgical group was 18%. with degenerative disk diseases.30 Although shown to be contro- versial, the diagnosis itself is usually made by provocative diskog- The authors concluded that the main outcome measure showed raphy at the level of the disk possibly causing the pain.19,20 An equal improvement in patients with chronic LBP and disk degener- et al3 discussed disk degenerative progressive changes as part of ation randomized to lumbar fusion or cognitive intervention and normal aging. Studies today cannot confirm what starts and what exercises.15 The risk for the nonsurgical group was considerably influences progression if no trauma or disease is present. There is lower, however, because no complications occurred. Although also debate about the disk as a pain source; from a clinical per- the evidence is less compelling than it might have been, in the spective, however, severe disk degeneration on several levels is future these patients may be offered surgery or CBT with similar shown to cause pain. Moderate to less visible disk degeneration results. This study needs to be confirmed by other and larger changes are more debatable. The authors argued for investigating studies, but it may provide an alternative to surgery when other sources of pain as well as its enhancers or modifiers. expected outcomes from that treatment are uncertain. A systematic literature review in 1999 concluded that there In a multicenter study from Great Britain,34 349 patients with was insufficient evidence for lumbar spine fusion in lumbar chronic back pain lasting more than 1 year were randomized to surgery (spinal fusion) or to an intensive rehabilitation program for 5 days a week for 3 weeks continuously and followed for 2 years. The team included a physician, a physical therapist, and a psychologist. The program was individually tailored to each patient with progressive exercises and CBT to overcome fears and negative beliefs about back pain. Both groups reported

132 Chapter 4d ● Treatment options reductions in disability, and the only primary outcome measure REFERENCES that marginally favored surgery was the Oswestry Disability Index, which showed a clinically insignificant decrease of about 1. Abenhaim L, Rossignol M, Valat JP, et al: The role of activity in the therapeutic man- four points on a scale of 100 (-.1 [95% CI, -4.1 to -0.1; p = 0.045). agement of back pain. Report of the International Paris Task Force on Back Pain. No clear evidence emerged that primary spinal fusion was any Spine 25:1S-33S, 2000. more beneficial than intensive rehabilitation. 2. Alexandre NM, Nordin M, Hiebert R, Campello M: Predictors of compliance with Randomized controlled trials on novel technology such as artifi- short-term treatment among patients with back pain. Rev Panam Salud Publica cial disks, electrothermal therapy, analgesic pumps, and implanted 12:86-94, 2002. stimulators are lacking. 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4eC H A P T E R chances emerge for unplanned events. These then result in various kinds of accidents with property damage and/or personal injuries. Workplace Adaptation A meaningful attempt to control such injuries makes it imperative for the Low Back Region to understand them. Shrawan Kumar and Steve Konz Most cases compensated by the Workers’ Compensation Board are regional musculoskeletal problems. Workers in differ- THE NATURE OF LOW BACK PAIN ent economic sectors generally have injuries characteristic of those sectors. People in forestry, construction, and manufactur- The nature of low back pain (LBP) and even its broad categoriza- ing have a higher proportion of back injuries. Those working in tion into acute, subacute, and chronic categories defy scientific office jobs involving keyboarding have cumulative trauma disor- precision. In many cases, its insidious onset, relief without med- ders (also called musculoskeletal disorders and repetitive strain ical intervention, recurrence despite all precautions, and eventual injuries). Because heavy physical workers do not develop repeti- chronicity have not only perplexed medical practitioners but also tive strain or injury of the upper extremity and office workers do posed an intellectual challenge even for a scientific conception not injure their backs, the argument can be made that the nature of the phenomenon. of the physical stress and the region enduring the load largely determine the affected area and probably the nature of injury. Although many risk factors have been associated with LBP, its If therefore one could delineate the mechanisms of injuries etiology remains obscure. Kumar14 categorized all known risk and the quantitative details of the relevant variables, one might factors into four broad categories: (1) morphologic, (2) genetic, develop a more effective intervention. An effective intervention (3) biomechanical, and (4) psychosocial. He stated that whereas would result in better control of injuries, which clearly has a sig- morphologic and genetic factors are hardly manipulable, the nificant payoff. Thus, the long-term success in controlling these biomechanical and psychosocial factors lend themselves to injuries depends on understanding their causality. manipulation. It was, however, conceded that all strategies must take into account the genetic and morphologic data for optimal Because for ethical reasons human beings cannot be sub- results. Many studies have been conducted to examine the pos- jected to controlled experiments exposing them to risk of injury, sible impact of different risk factors, but the human back is Kumar et al16 performed an integrative synthesis of information like a multilink chain that is only as strong as its weakest link. in the scientific literature to formulate biologically plausible the- Unfortunately, the weakest link is most elusive, being different in ories as to the mechanisms of injury causality. Through this exer- different people and also at different times in the same individual cise they proposed four theories of musculoskeletal injury causality because of varying internal and external circumstances. described briefly below. 1. The Cumulative Load Theory16: Because biologic tissues are CAUSAL MECHANISMS AND CONTROL composed of both solid and liquid, their combined mechan- Humans have evolved over millions of years into what they are ical behavior or viscoelasticity is determined largely by the today. Evolutionary pressures and consequent speciation resulted proportion of these components. Biologic tissues therefore in an upright biped creature with dextrous upper limbs and a deform partially like solids and partially like liquids in a highly evolved brain. For a large duration of its existence, the blended manner. Such properties are time dependent: a longer species relied on hunting and gathering as its primary means of exposure to the same load will produce larger deformation sustenance.5 With the advancement of science, technology, and and vice versa. As a result, recovery from deformation takes industrialization, the physical occupational stresses have changed time also. If the succeeding load does not allow sufficient dramatically in an evolutionary “flash” so that none of the body recovery time, the tissue begins to deform further from its com- systems that one uses today was either designed or evolved for the promised stage. As demonstrated by Kumar13 in an epidemio- current purpose. As a result, demand for force exertion, activity logic study, repeated loading results in a cumulative effect of repetition, or posture assumption for prolonged periods places reduced threshold to failure. stress on human physical systems that is inherently unnatural. 2. The Differential Fatigue Theory16: Occupational tasks are kine- This is further aggravated by many psychologic stresses emanating siologically complex and hardly ever performed in one plane. from financial or interpersonal factors. Asymmetric activities requiring the use of many body parts of the bilaterally symmetric human organism result in differential In addition, most human occupations have become complex, unequal loads on various muscles, joints, and connective tis- requiring significant organization and thereby enhancing the sue. One task may stress one tissue element to 80% of its capac- chances of errors. As a function of a multivariate complex system ity, whereas another one is stressed only 10%. Additionally, this (in many cases under multiple partial controllers), significant distribution is not determined by the tolerance of the tissue con- cerned. Such diverse distribution of stress results in one muscle becoming more fatigued than others.15,16 This differential fatigue causes loss of coordination resulting in sudden and significant stress concentration that precipitates an injury. 3. The Overexertion Theory16: The basic tenet of this theory is that even a rested and normal tissue can, and probably will, fail when the stress/load exceeds its tolerance time. Although stressed and fatigued tissues cannot withstand stress concen- tration, it is not necessary for tissues to reach that stage to fail.

136 Chapter 4e ● Workplace adaptation for the low back region 4. The Multivariate Interaction Theory16: Over and above the problem because of the alleged secondary gain. We have been the three previous theories, the variability in the individual able to reduce neither the incidence nor the severity of LBP; a threshold indicates also that a precipitation of musculoskeletal cure neither exists nor is likely to emerge in the foreseeable future. injury may be modulated by the interaction of genetic, mor- No difference in long-term outcome between aggressive and con- phologic, psychosocial, and biomechanical factors. Within servative treatments has been identified, and we seem unable to each of these categories are many variables that may potentiate control the problem in a significant or meaningful way. LBP is an injury. Interaction between the relative weights of the vari- clearly here to stay. ables and the extent to which these have been stressed in any given individual determines the final outcome. It is therefore of utmost importance to focus on workplace adaptations to reduce human suffering and economic cost. Our Although these four theories have been presented as distinct, endeavor to identify these adaptations must try to reduce the mag- all four are simultaneously operative but to a different degree nitude of identified risk factors and the exposure of workers to depending on the circumstances and individuals. As pointed out them, decrease the incidence of LBP in healthy people, and reduce above, humans have not evolved over the past 250 million years stress in patients who already have the condition. Such adapta- to be industrial workers. Humans will therefore always find tions will be helpful in returning workers to work after injury. themselves in the middle of a conflict between their nature and an industrial requirement. Such a backdrop clearly makes occu- DISABILITY CAUSED BY LBP pational injury prevention not only a daunting and lofty goal but an unachievable objective. Control of injuries to reduce their LBP is associated with considerable disability that results in work incidence and severity, however, remains a goal that may be loss, its most important social and economic consequence achieved to varying degrees. With this in mind, Kumar12 presented despite the influence by many other factors. A direct correlative a strategy to quantify the risk based on the discrete physical scale between LBP, disability, and work loss has not been estab- elements of the task in question. lished. A simple clinical and subjective assessment of disability, however, has been claimed to have considerable relevance to THE EXTENT OF THE PROBLEM quality of life as well as industrial performance. This assessment is focused on loss of function rather than pain. The emphasis is As a medical condition LBP has only one redeeming feature—it on whether an activity can be performed by an individual or is is not fatal. In spite of the obscurities associated with its etiology, restricted because of LBP. Implicit in this assumption is that the classification, and treatment, human and economic impacts have restriction must have its onset coincident with that of the back been approximately quantifiable. Chapter 4a on the epidemiology pain and must therefore be the functional limitation. The specific of LBP offers a comprehensive picture of the problem; suffice it criteria used by Waddell et al21 are as follows: to say here that it is a large social and economic one. Although 1. Bending and lifting it occurs in less developed countries also, the impact of LBP is 2. Sitting much more recognized in Western and industrialized countries. 3. Standing 4. Walking To put the extent of the problem in perspective, a brief 5. Traveling description follows. Andersson1 stated that national statistics 6. Social life from the European countries reveal 10% to 15% of all sickness 7. Sleep absence to be due to back pain, with the number of work days 8. Sex life lost per worker increasing steadily. An annual prevalence of 25% 9. Dressing/undressing to 45% was reported, and chronic back pain was present in 3% to 7% of the adult population. The lifetime prevalence of LBP The aforementioned criteria combine postural, strength, meta- has been variously reported as between 70% and 80%. In Canada, bolic, and everyday living activities that are involved also in occu- LBP has steadily constituted approximately 27% of all industrial pational activities. LBP and loss of function through disability are injuries; these have been reported to cost disproportionately higher results of biomechanical (kinematic and kinetic) perturbation of amounts than all other injuries. the human system. These demands are covered in Chapter 4b, but we note here that the functional activities accentuating these In the United States, the annual prevalence has been reported demands are divided into two main categories: static load (sitting, to be in the 15% to 20% range. Khalil8 reported that on any given holding) and dynamic load (pushing/pulling, carrying, and lifting/ day, roughly 75 million Americans have back pain, 6.5 million of lowering). The concentration must therefore be on those activities whom are in bed. Webster and Snook23 reported the cost of LBP in that reduce hazards for initial injury and subsequent recurrences. 1989 incurred by Liberty Mutual, the largest insurer in the United States; it constituted 16% of the claims and accounted for 33% of ADAPTATIONS the total expense. They reported also that the mean cost per case of LBP was $8300 compared with $4100 for all other claims com- Static work bined, whereas the median cost was $396 ($168 for other claims). In these claim settlements, 34% of the total cost for LBP was med- Spitzer et al20 report the LBP incidence in Quebec, Canada of ical, whereas 66% was indemnity cost for lost time and wages.23 individuals required to do heavy work but also include sedentary No matter which way one looks, LBP is prevalent and expensive. Some of the socioeconomic aspects of our society may accentuate

Chapter 4e ● Adaptations 137 work areas such as “government, wholesale and retail, and finance stools; both conventional and sit/stand chairs should have back- and insurance.” Magora17 reported on LBP for bank tellers and rests. Sit/stand chairs should have a forward tilt of 15-30 degrees for those who perform heavy work. and a fabric seat.4 Seated work Another technique to encourage movement is job rotation. A chair is the key component of seated work, but because not all Problem seated work is the same, chairs should be matched to specific jobs. Of course, people vary in height and weight, and many of Because intervertebral disks are avascular, their nutrition depends them often sit in the same chair because of multiple shifts, part- entirely on diffusion. Intervertebral disks also are viscoelastic. time workers sharing a shift, and holiday or vacation replacements. While an individual is sitting, the load on the intervertebral disk Thus chairs should be easily adjustable in terms of seat pan is 140% of that imposed by standing. This static load progres- height, back rest height and forward/back location, and armrest sively decreases the water content of a disk; an increased load width and height. The seat should be padded with a breathable accelerates this process. Loss of water from a disk makes the fabric; avoid plastic and leather. It should not be contoured, diffusion process more difficult and results in reduced oxygen because this reduces micropostural changes. A curved front edge tension and lack of nourishment, leading to disk degeneration. (waterfall front) maximizes contact with the underside of the thigh; avoid upholstered beading on the front edge. Normally, Sedentary occupations involve prolonged exposure to static the seat should tilt backward 1-5 degrees and permit swiveling. loads, hastening this process and making the disk more vulnerable For seat width, the wider the better; for depth, the most common to injuries. A constant static load also deforms the viscoelastic disk problem is a seat that is too deep. A deep seat forces the sitter and causes compression creep. Because creep is time dependent, forward (losing support of the backrest) or back (with the legs elimination of a load does not immediately restore either the pre- dangling). The ideal backrest is adjustable both horizontally and load disk configuration or the water content. The reduction in vertically and has a spring action so that it “tracks” the angle of water and oxygen is therefore prolonged, interfering with disk the back as the person moves. It should be concave to give area metabolism by decreasing the amount of glycosaminoglycans support to the back, especially in the lumbar region. Armrests (which have a strong affinity for water) and increasing the content should be adjustable in width and height. Avoid long armrests that of keratan sulfate (which is amorphous with far less capacity to hit the table edge and preclude good chair location with respect to imbibe water). In the short term, the viscoelastic deformation may the task. The legs/pedestal normally should permit swiveling and lead also to laxity of the ligament and lack of coordination, poten- thus micropostural changes. The sitter’s legs should be able to tuck tiating injury through biomechanical perturbations. Over the long under the seat to shorten the hamstrings (reducing their pull) and term, it leads to degenerative and permanent changes that are a decrease stress on the back. If the seated worker moves about the hazard to the back. work station, the chair should have casters; otherwise, they are inadvisable because they force the operator to use leg muscles to The problem of seated sedentary work worsens considerably keep the chair still. Design modifications to truck seats should when prolonged sitting is combined with whole-body vibration, reduce vibration at the point of origin or dampen it before trans- such as with truck driving. The frequencies of many vehicles are mission to the driver. Trucks should be equipped with hoists and close to the natural frequency (4 to 8 Hz) of the human spine, dollies to reduce acute stress on the back by doing the work. causing resonance and thus amplification of the motion ampli- tude. Truck drivers must contend not only with this vibration Holding work but also with the static loading of the disk while driving. In addi- tion, often they have periodic acute loading of the back when Problem they load or unload their vehicles. For some tasks in auto assembly, painting, or kitchen and laundry Control strategies work, for example, workers hold an object without movement. Even without an object, the weight of one hand and arm is The two strategies for addressing this problem are personal com- approximately 4.9% of body weight. The farther from the spine pensations and job design. From a personal viewpoint, people in the hand or object, the greater the problem, because torque is a sedentary jobs should lead active lives outside the workplace. In product of weight times moment arm. addition, at work they should be encouraged to change postures frequently, move around, and mix nonseated with seated work. Control strategies (Naturally, the job design should not just permit this movement but also encourage it.) To address this problem, reduce the torque and its duration. Figure 4e.1 shows how a tipping aid can reduce the strain of Job designs of seated workers often include either machines or holding a drum or container. An angled bar (a “plow”) on a belt other workers to bring supplies and remove finished products. conveyor can direct a product on the conveyor toward the side By not allowing the worker to move, this practice creates a closest to the worker, who need not reach as far for the item and “straight jacket” that precludes movement. Permitting a worker therefore reduces torque on the spine. For standing workers, a to fetch supplies and dispose of products not only is beneficial conveyor should be about 50 mm below the elbow (by height but also should be encouraged within limits. Another possibility adjustment or by having short operators stand on platforms) to for permitting some movement is to have a sit/stand work minimize torque on the arms and back. A balancer (Fig. 4e.2) station where the worker can alternate between sitting and stand- reduces tool weight. ing. Standing work is better if there is a “bar rail” or footrest upon which the worker can alternate foot positions.9 Avoid using

138 Chapter 4e ● Workplace adaptation for the low back region Dynamic work Manual handling is quite prevalent in industry. Asfahl2 estimated that for every pound of product, 80-150 pounds of materials are handled and moved. Konz and Johnson9 stated that 25% of all industrial injuries are associated with manual handling—670,000 injuries per year in the United States. Of money spent on industrial injuries, 60% pays for those caused by manual handling, which accounts for 93,000,000 work days lost each year. Dynamic work risks are divided among pushing/pulling, carrying, and lifting/ lowering, the last of which causes most problems. Pushing and pulling Imrhan7 provided an excellent summary of pushing/pulling. Pushing occurs not only while standing but also while sitting and even kneeling. Height and direction also are important (Fig. 4e.3). Figure 4e.1 Tipping aids permit a drum or carboy to be counterbalanced Control strategies when pouring. The danger of spills and operator muscle stress is reduced. A poor interface of the hand and handle is a potential weak link. Although a handle is needed for pulling, pushing may just use a flat surface. Two hands are better than one. The arm and shoulders (rather than the back) tend to be limiting (causing local muscle fatigue) when the activity is repetitive. Workers should avoid push- ing or pulling above the shoulders or below the hip. Effective pushing involves leaning toward the load with the rear foot posi- tioned behind the body’s center of mass (Fig. 4e.4), whereas pulling involves leaning away from the load with the rear foot behind the body’s center of mass. Although there should be a high coefficient of friction between the floor and the shoe, the object may have a low coef- ficient of friction against its supporting surface. Ball transfer sec- tions on conveyors have a kinetic friction of 0.03 to 0.15, for example, so pushing a 50-kg container on balls requires a force of 1.5 to 7.5 kg. Air-film pallets use the same concept of reduc- ing the friction of object against surface. Generally, people push/pull perpendicular to the shoulders. When pushing parallel to the shoulders, the capability is 50-60% of the perpendicular capability. Several recommendations for force limits for pushing and pulling have been published.18,19 In summary, ● Two hands are usually better than one. ● Force capability decreases when it is used more often. ● Initial force capability is higher than sustained capability. ● Pushing capability is higher than pulling capability. ● Pushing should be done at waist level and pulling at thigh level. Figure 4e.2 Balancers reduce tool weight from pounds to ounces. Carrying Note that the balancer is suspended from a job crane to minimize horizontal force as the tool is moved about the workplace. The greater Although carrying objects for long distances (those over 10 m) tool weight increased torque at the elbow and shoulder, thereby no longer is common in developed countries, workers still carry decreasing comfort of the neck and back as well as the arm (Ulin S, around work stations. Carrying objects up and down stairs is Armstrong TJ, Snook SH, Monroe-Keyserling W: Examination of the especially dangerous because the hands are holding the object effect of tool mass and work postures on perceived exertion for a and thus not free to grasp handrails if there is a slip and because screw driving task. Int J Ind Ergonom 12:105-115, 1993). the object may obstruct vision. Control strategies Long-distance carrying is best when mechanized with lift trucks, conveyors, or carts (Fig. 4e.5). As anyone who has transported a

Chapter 4e ● Adaptations 139 Figure 4e.3 Chiming a drum (rotating a tipped drum) requires little effort; with skill, the drum’s momentum can be used to move it onto a pallet. A drum cart is another alternative. A straight push, however, as shown on the right, requires considerable effort. suitcase through an airport knows, pushing or pulling is better multiplier, and CM is the coupling multiplier. Konz and than carrying, so wheels should be used whenever possible. Johnson9 explain the calculation procedure in detail, and the Jib cranes, ball-transfer sections, or manipulators (Fig. 4e.6) can disk accompanying the book has a computer program to solve move objects within work stations, as do ramps and elevators the equation. between floors. Control strategies Lifting and lowering 1. Select strong people based on tests: Several studies have As pointed out above, manual handling creates many problems. shown the significance of the job severity index, the ratio of Engineers and ergonomists can focus on the job-specific factors the task demand to the person’s capability. One approach with reference to the detailed tables of the manual handling may therefore be to select workers with large capacities. It is guide.18 For example, Table 4.2 of the guide gives 720 recom- important to consider worker capacity in job-simulated tests, mended weights for male industrial workers for two-handed sym- which force the analyst to measure not only this factor but metric lifting for 8 hours. The table has three box sizes, eight lifting also the task requirements. frequencies, six lifting distances, and five population percentiles. The most common approach is that set forth in the National 2. Bend the knees: Despite a concerted effort to train workers to Institute for Occupational Safety and Health (NIOSH) lifting lift with bent knees and straight backs, the practice has not guideline.22 The NIOSH guideline assumes a load of 23 kg but received universal acceptance. The logic behind the recom- then reduces the 23 through 6 multipliers (all less than 1.0) to mendation has been to reduce the moment arm on the lum- arrive at a recommended weight limit (RWL): bosacral disk, thereby reducing mechanical compression. It has been shown, however, that unless the object to be lifted RWL = LC × HM × VM × DM × FM × AM × CM is brought very close to the body, the squat lift can in fact significantly increase mechanical compression on the lum- where LC is the load constant (i.e., 23 kg), HM is the horizontal bosacral disk. It has been shown also that the squat lift is asso- multiplier, VM is the vertical multiplier, DM is the distance mul- ciated with significantly higher physiological cost and is more tiplier, FM is the frequency multiplier, AM is the asymmetry tiring for workers. Typical posture Recommended posture Figure 4e.4 Posture when pushing makes a difference. Peak intraabdominal pressure was 50% less when pushing with the back (Ridd J: A practical methodology for the investigation of materials handling problems. In T Kvalseth, ed: Ergonomics of work station design. London, 1983, Butterworth-Heinemann).

140 Chapter 4e ● Workplace adaptation for the low back region A C B Figure 4e.5 Drum carts reduce stress. (A) A two-wheeled cart; it should have a latch over the top rim during movement. (B) The foot can be used to help tip the drum. Another handle forward of the main handles is useful when tilting and maneuvering the drum to scales and pallets. (C) A four-wheeled cart useful for heavier drums; note that the hand positions are different. Another disadvantage of the squat lift is that it causes con- 3. Don’t slip or jerk: Sudden and ballistic movements have a siderable stress on the knees, which are also a frequent site of large inertial component. Because of the viscoelastic nature of mechanical disorders. Therefore a universal acceptance of the the human back and the resistance to immediate deformation squat (as opposed to the stoop) lift is neither physiologically offered by the fluid portion of the tissue, such inertial forces nor mechanically sound. It is perhaps for this reason that this can exceed the tolerance limits of the tissues.16 In addition, method has not been accepted by workers as widely as was sudden motion may also cause a slip or fall while performing initially hoped. Furthermore, the statistics of low back injuries a lift. It is therefore recommended that workers wear shoes associated with lifting over the past 40 years make clear that a with soles having a large contact area and a high coefficient steady increase in incidence has occurred despite many indus- of friction, as should floors, which must not be smooth. Data trial workers’ following the squat method. It is important to on a force platform indicate that peak forces and torques dur- assess the job as well as the individual performing it before ing lift are very “spiked,” with the peak force often occurring recommending squat or stoop lifting. during initial lowering of the body before the object is even grasped. The accelerations and decelerations during lifting Garg et al6 compared the physiologic costs of different meth- and lowering should be fast enough that the body gets the ods of lifting. They found that when subjects were allowed to benefit of the momentum without causing a jerk that may lift any way they wanted, they chose neither pure stoop nor lead to an injury. pure squat but combined the features of both in a freestyle lift. This lift was found to be metabolically the least expen- 4. Avoid twisting: To maintain symmetry of the human body, sive. The recommendation is therefore to use an individual- the spine is provided with a bilaterally symmetric arrange- and task-specific method to minimize stress on spine and ment of muscles and ligaments. Any rotation accentuates reduce the chances of injuries. the activities in the agonist group of muscles and reduces the

Chapter 4e ● Adaptations 141 Figure 4e.6 Manipulators (balancers with arms) can support tools or of injury. Twisting while bent over, such as when removing can be used to move products around work stations. parts from the floor, is risky. A general recommendation is therefore for workers to move their feet instead of twisting their backs. Because workers might not comply as rigorously as desirable, an engineering approach precluding the need to twist is recommended. Such an approach will solve the prob- lem rather than depend on the workers’ knowledge, aware- ness, alertness, and cooperation. Figure 4e.7 shows how a task can be modified to reduce bending and twisting. 5. Use mechanical aids: The most desirable means of preventing injuries associated with manual materials handling is to elim- inate it by using mechanical aids. Instead of moving a power tool around a work station, for example, a balancer (Fig. 4e.2) or manipulator (Fig. 4e.6) can be used. Figure 4e.8 shows a turntable on a scissors lift used to mechanize palletizing; in automation, the operator would be replaced with a palletizer. In some circumstances robots are appropriate. Other machines commonly used to eliminate manual handling are hoists, lift trucks, conveyors (both portable and telescopic), and lever arms. 6. Consider the packaging: For job design, an important con- cept is to keep the load close to the body, so it is important to keep packages small. Big, bulky, and awkward packaging increases the moment arm of the load on the spine, thereby increasing the compressive load significantly. Bulk may make it more difficult to lift 25 kg of feathers, for example, than 25 kg of iron. Konz and Coetzee11 reported that increasing a box’s volume up to a 30-cm cube did not bother men but strongly bothered women. When determining packaging dimensions, it is therefore important to consider the anthropometry of the work population. 7. Have good coupling: Cardboard boxes with cutout holes pro- vide poor coupling because (1) the hand cannot rotate as the object is lifted from the knee to the waist and (2) the narrow cardboard surface area tends to concentrate the load on a small area of contact with the hands, thereby cutting the circulation and squeezing the muscles. When the packages to be lifted are larger than optimal size, it is particularly important to provide a comfortable handhold to permit a relatively risk- free, orderly, and smooth lifting activity that minimizes the chance of injury. 8. Consider work height and reach: Konz stated, “Drag it, pull it, push it, but don’t lift it.”10 As explained above, if lifting is necessary, it is best done at knuckle height; loads should not be on the floor or above the shoulders. When cartons are loaded from a conveyor, for example, the conveyor height should be adjustable. When they are loaded from a pallet, it should be left on the lift truck forks, the height of which should be periodi- cally adjusted. If the fork lift cannot be tied up, the pallet should be placed on a wheeled lift table. contribution of the antagonistic muscles. When manual A summary of all these principles has been provided by materials are handled, a twisted posture or when the spine is Ayoub et al3 in a comprehensive set of guidelines to control and progressively twisted during a lift, the force production in dif- reduce occupational health problems associated with manual ferent muscles is continually varied, accentuating the stress materials handling. Their recommendations can be summed up on one group of muscles and ligaments. When most of in two statements: (1) eliminate heavy manual materials han- the load is borne by only 50% of the structures, the stress dling and (2) decrease the stress to the worker. They recommend could easily be doubled, significantly increasing the chances the use of mechanical aids such as hoists, lift tables, and convey- ors and the provision of best work heights that can be varied to suit the operator and achieve an optimum work arrangement.

142 Chapter 4e ● Workplace adaptation for the low back region Figure 4e.7 Work station positioners reduce lifting, bending, and twisting. (A) A scissors lift. (B) A bin on an adjustable-height cart that is useful to create temporary work stations for tasks such as shelf stocking. (C) A self-leveling truck (similar to cafeteria tray dispensers). Figure 4e.8 Turntables can reduce stress when loading or unloading. The turntable is rotated after a few items are moved. It can be mounted on the floor and a pallet placed upon it. If the turntable surface is rollers, ball casters, or an air table, rotation can be manual. If it is mounted on a scissors table (as shown), horizontal transfer can replace lifting and lowering.

Chapter 4e ● References 143 A reduction of stress, they suggest, can be achieved by reducing 7. Imrhan S. Push-pull force limits. In W Karwowski, W Marras, eds: The occupational the weight of the object in cases in which it is not possible ergonomics handbook. Boca Raton, 1999, CRC Press. to split the load between two workers. A reduction in the size and weight of containers is a desirable goal also. The authors 8. Khalil T: Ergonomic issues in LBP: origin and magnitude of the problem. Proceedings recommend changing the type of manual materials handling: of the Human Factors Society, San Francisco, 1991, pp. 820-824. lower the load rather than lift, push the load rather than pull, and pull the load rather than carry. They suggest reducing both the 9. Konz S, Johnson S: Work design: occupational ergonomics, ed 6. Scottsdale, AZ, horizontal and vertical distance in reaching for an object and 2004, Holcomb Hathaway. transporting it. Avoiding twisting in both standing and seated work is desirable. Modification of an object to make it easier to 10. Konz SA: Work design: industrial ergonomics, ed 4. Scottsdale, AZ, 1995, Publishing handle by using handles, balance containers, and reasonable Horizons. width are all good design criteria. On the worker side, however, it is important also to provide adequate recovery time by reduc- 11. Konz SA, Coetzee K: Prediction of lifting difficulty from individual and task variables. ing the frequency with which a particular task is performed and Proceedings of the Fourth International Congress on Production Research, Tokyo, allowing for job rotation. 1977. REFERENCES 12. Kumar S: A conceptual model of overexertion, safety and hazard. Hum Factors 36:197-209, 1994. 1. Andersson GBJ: The epidemiology of spinal disorders. In J Frymoyer, Spitzer W, LeBlanc FE, Dupuis, M eds: The adult spine. New York, 1991, Raven Press, 13. Kumar S: Cumulative load as a risk factor for back pain. Spine 15(12):1311-1316, pp. 107-146. 1990. 2. Asfahl CR: Industrial safety and health management. Englewood Cliffs, NJ, 1984, 14. Kumar S: Functional evaluation of the human back: a research report. 1991. Prentice Hall. 15. Kumar S, Narayan Y: Spectral parameters of trunk muscles during isometrics axial 3. Ayoub MM, Selan J, Jiang B: Manual material handling. In G Salvendy, ed: Handbook rotation in neutral posture. J Electromyogr Kinesiol 8:257-267, 1998. of human factors. New York, 1987, Wiley & Sons. 16. Kumar S, Narayan Y, Stein RB, Snijders C: Muscle fatigue in axial rotation of the 4. Chester M, Rys M, Konz S: Leg swelling, comfort and fatigue when sitting, standing, trunk. Int J Indust Ergon 28:113-125, 2001. and sit/standing. Int J Indust Ergon 29:289-296, 2002. 17. Magora A: Investigation of the relation between LBP and occupation. Ind Med 5. Davis PR: The biological basis of physiological ergonomics requirements. Int J Indust 39(12):504-510, 1970. Ergon 23:241-245, 1999. 18. Mital A, Nicholson A, Ayoub MM: A guide to manual material handling. London, 6. Garg A, Sharma D, Chaffin DB, Schmidler JM, et al: Biomechanical stresses as related 1993, Taylor & Francis Publishers. to motion trajectory of lifting. Hum Factors 25(5):527-539, 1983. 19. Snook SH, Ciriello VM: The design of manual handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics 34(9):1197-1213, 1991. 20. Spitzer W, LeBlanc FE, Dupuis, M: Scientific approach to the assessment and management of activity-related spinal disorders. A monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 12(Suppl):1-559, 1987. 21. Waddell G, Allan DB, Newton M: Clinical evaluation of disability in back pain. In JW Frymoyer, Spitzer W, LeBlanc FE, Dupuis, M eds: The adult spine. New York, 1991, Raven Press. 22. Waters T, Putz-Anderson V, Garg A: Application manual for the revised NIOSH lifting equation. NIOSH Pub PB94, Rockville, MD, 1994, Department of Health and Human Services. 23. Webster BS, Snook SH: The cost of 1989 workers’ compensation LBP claims. Spine 19(10):1111-1115, 1994.

Appendix 4e.1 Websites of workstation suppliers Advance Lifts (work station positioners) www.advancelifts.com Glasgow (air tables) www.glasgowproducts.com American Lifts (scissors lifts) www.americanlifts.com Knight Industries (balancers, manipulators) www.knight-ind.com Autoquip (lifting, turning, tilting equipment) www.autoquip.com Presto Lifts (work station material handling) www.prestolifts.com Bishamon Industries (pallet positioners, lift tables) www.bishamon. Rampmaster (work station material handling) www.rampsonline. com com Columbus McKinnon (lift tables) www.cmworks.com Scaglia America (balancers, manipulators) www.scaglia.it Columbus McKinnon (manipulators) www.positech-solutions.com Southworth (work positioning) www.southworthproducts.com Econolift (lifts/tilters) www.econolift.com Tawi USA (vacuum lifting) www.tawi.se Ergonomic Systems (work station/positioners) www. Vestil (work positioning) www.vestilmfg.com ergonomisystems.com

5C H A P T E R Shoulder and Elbow

5aC H A P T E R of the elbow. Cubital tunnel external compression syndrome is caused by compression of the ulnar nerve at certain elbow Shoulder and Elbow flexion angles at a subcutaneous location behind the humeral Disorders epicondyle (cubital tunnel). Marianne Magnusson and Malcolm Pope EPIDEMIOLOGY This chapter discusses the epidemiology and pathomechanisms General population of disorders of the shoulder and elbow. Shoulder and elbow dis- orders were reported as related to certain occupations as long ago In general studies that include large sample populations without as 1713.80 Like other musculoskeletal disorders (MSDs), those of special demands for neck and shoulder activity, the 12-month the upper extremity are increasing, as expressed by a more fre- prevalence of neck and shoulder disorders was 15% to 18%.5,94 quent reporting of them as occupational diseases.65 The reason Disorders of the neck and shoulders are most common among for the increase might be the higher degree of automation result- women.7,21,93,94 In a Swedish study, 50% of the women but ing from workplace designs improved to reduce heavy workloads only 36% of the men reported strain injuries from the neck and like lifting and manual labor. The demands of increasing produc- shoulders.44 Another study reported a 10 times higher rate of sick tivity, however, which in turn imply the simplification of work- leave due to occupational cervicobrachial disorders in women ing tasks, has increased the work pace.96 compared with the sick leave in men due to occupational low back pain.51 Perhaps even more than men, women often work in CLASSIFICATION OF DISORDERS occupations with repetitive and monotonous work tasks, and many studies have reported an increased prevalence of upper Shoulder limb disorders in repetitive work.32,47,58,78,92 In a large Swedish study of 2537 men and women, 20% of the women and 16% of In the International Classification of Diseases,99 work-related the men had neck-shoulder problems during the last 12 months,92 neck-shoulder disorders have been classified into “occupational the incidence of which increased with age and occupational diseases,” in which there is a direct cause-effect relationship physical load. Takala et al reported a 1-year prevalence of 18% between hazard and disease, and “work-related disease,” in which of women and 16% of men in a Finnish rural population.89 In work environment and the performance of work contribute a random sample of 855 men and women in Iceland, 65% of significantly, but as one of a number of factors, to the causation the women and 43% of the men had neck or shoulder pain of a multifactorial disease.98 during the previous year.79 Neck and shoulder pain has been found to be not only interrelated but also related to low back The concept of occupational cervicobrachial disorder was pain, indicating a susceptibility and a predisposition to develop adopted in 1973.6,61 It is defined as “functional and/or organic MSDs.63 disturbances resulting from neuromuscular fatigue to doing jobs in a fixed position or with repetitive movement of the Occupational risk groups upper extremities.” Waris93 named four categories: the cervical syndrome, the tension neck syndrome, humeral tendinitis, and Epidemiologic studies show, and most researchers agree, that thoracic outlet syndrome. along with personal factors such as age, genetics, and gender, exposure to a combination of physical and psychosocial work- Introduced in Australia, the term repetition strain injury is place risk factors is a major contributor to these disorders. defined as “a soft tissue disorder caused by muscle overloading Specific physical factors include intense, repeated, or sustained from repetitive use or maintenance of constrained postures” that exertions; awkward, sustained, or extreme body postures; insuffi- “occurs among workers performing tasks involving frequent cient recovery time; vibration; and cold temperatures. Specific repetitive movements of the limbs or the maintenance of fixed examples of workplace psychosocial factors include monotonous postures for prolonged periods.”12 Cumulative trauma disorder, work, time pressure, high workload, lack of peer support, and a musculoskeletal injury and disorder, occupational repetitive poor supervisor-employee relationship.34 strain injury, and regional pain syndrome are other terms that describe essentially the same condition. Musculoskeletal diseases were the major reason for long-term absenteeism in a manufacturing company. Low back pain Elbow accounted for 17.7% of all long-term absenteeism (the greatest amount), and neck and shoulder pain caused 15.9%. Back disor- Tennis elbow, also called lateral humeral epicondylalgia or lateral ders were most common in heavy manufacturing workshops, elbow syndrome, is a painful condition of the lateral aspect whereas in the light manufacturing workshops the most domi- nant diseases related to the neck and shoulder.51 As recorded in a questionnaire and compared with a control group with more varied tasks, females employed in assembly, fish-processing, and ceramics factories, all representing highly repetitive work tasks, had considerably higher prevalences of

150 Chapter 5a ● Shoulder and elbow disorders Table 5a.1 Elbow problems in newspaper workers associations with a combined exposure to repetition and (% of total)82 awkward posture. All Office Production The principal muscle to carry this load is the trapezius. The relative load as a percentage of maximum voluntary contraction 12-month 8 6 12 (MVC) on the upper trapezius has been shown to increase lin- prevalence (%) 1 1 2 early with the relative torque in the glenohumeral joint.29 There Missed work (%) 906 682 are large differences, however, among muscles and between flex- n 201 ion and abduction. A given shoulder torque during flexion pro- duces smaller amplitudes of both the intramuscular pressure and complaints and physical examination diagnoses of neck and the EMG than for the same torque during abduction.38 With a upper limb disorders.70 shoulder abduction of 30 degrees, the intramuscular pressure in the supraspinatus muscle by far exceeds the level at which the Without a specific diagnosis or defined symptoms, neck blood flow is significantly impeded. The supraspinatus is thus and shoulder problems have been reported in a large number of extremely vulnerable in work situations requiring arm elevation. studies involving secretaries and office workers,10,41,42,56,91 den- High shoulder muscle force requirements can cause increased tists,55,68 sewing machine operators,86 visual artists and piano muscle contraction, which may lead to an increase in both mus- players,16,27 and railway station workers.13 The annual prevalences cle fatigue and tendon tension and may possibly impair micro- of neck and/or shoulder symptoms for female secretaries and circulation as well. Sjøgaard et al86 found that muscular fatigue office workers ranged from 45% to 63%, whereas those for male would occur at EMG levels as low as 5% of MVC if sustained for office workers were considerably lower, ranging from 16% to 1 hour. Other studies have demonstrated that when the period 27%. Table 5a.1 reports the elbow problems found in a study of muscle contraction is extended to more than an hour, the surveying workers in the newspaper industry.82 endurance limit of force may be as low as 8% MVC.40 Workers performing repetitive work with the hands and wrists while Musculoskeletal problems in instrumental musicians have a maintaining static upper arm elevation may experience fatigue long history.25,26 Lederman and Calabrese52 described an increas- even at low load levels. Jonsson et al40 reported that many con- ing number of reports of musculotendinous overuse. Nerve strained work situations are characterized by static load levels entrapment syndromes have been reported in musicians by near or exceeding 5% MVC even when there is a fairly low mean Knishkowsky and Lederman.48 Charness et al17 reported that muscular load. routine electromyography (EMG) and nerve conduction studies were abnormal in less than half the musician patients studied, Ohlsson et al71 reported an odds ratio of 3.03 (95% confidence attesting to the potential for even mild ulnar neuropathy to interval, 2.5-7.2) for supraspinatus, infraspinatus, or bicipital ten- produce disabling symptoms. dinitis for work in the fish industry, representing repetitive work and poor posture. Compared with that of a referent population, RISK FACTORS the odds ratio for assembly work, which requires repetitive arm movements with static shoulder load, was 4.2 (95% confidence Work-related factors interval, 1.35-13.2). Work-related factors recognized for their association with upper Kurppa et al,50 Silverstein et al,85 and others reported that limb disorders include repetitive or forceful exertions, awkward highly repetitive tasks can cause pain and disability in the upper postures, and segmental vibration. Several studies have suggested extremity. In many jobs, upper extremity tasks require repetitive a relationship between static and/or repetitive load and disorders contractions of those muscles over long periods of time at low in the neck and upper extremity.30,44,51,60,95 In their meta-analysis contraction intensities and short contraction-relaxation cycles. of occupational neck-shoulder disorders, Hagberg and Wegman32 Silverstein et al85 created a prevention index to rank industries by found that jobs with highly repetitive shoulder muscle contrac- averaging the ranks of their number of claims and their claims tions, static muscle work, and work above shoulder level were incidence rate with a focus on nontraumatic soft tissue MSDs. associated with the tension neck syndrome. Kuorinka and Although the incidence rates for some disorders are decreasing, Forcier49 looked specifically at shoulder tendinitis and stated that the overall rate is not decreasing as fast as that for all other claims. the epidemiologic literature is “most convincing” regarding work In some cases, the rate is stable (sciatica, rotator cuff syndrome) relatedness, showing an increased risk especially from overhead or increasing (epicondylitis). and repetitive work. The industries with the highest risk are characterized by heavy Several studies have supported these associations4,16,27,72,86; the manual handling and repetitive work. Edwards22 proposed that mechanical load on the shoulders was obvious, and working fatigue and lack of recovery are the elements that can cause tasks involving continuous arm movements always generate a injury to the elbow. In simulations of upper extremity work static load component.1,72,85,97 Repetitive work should therefore measuring recovery of blood flow, EMG fatigue index, and not be considered independent of posture. Association between subjective ratings, Byström and Kilbom15 concluded that a mean repetition and shoulder tendinitis has been reported in three contraction intensity of higher than 17-21% MVC was not studies,23,71,73 in all of which some or all of the results showed acceptable. Using the same techniques, Byström and Franson- Hall14 suggested in a later article that continuous handgrip con- tractions higher than 10% MVC are to be avoided. These recommendations are conservative, and many industrial jobs exceed the safety limits.

Chapter 5a ● Pathomechanisms 151 Overall, epidemiologic evidence suggests a relationship in proportion to their muscle strength,10,84 but this has not been between repeated or sustained shoulder postures with more than proven for all muscle groups. Although women may have more 60 degrees of flexion or abduction and shoulder MSDs, including neck-shoulder disorders than men because of fatigue and poor both tendinitis and nonspecific pain. The evidence for increased strength, it is more likely because women predominate in jobs risk of MSDs due to specific postures is strongest with a combi- involving a high degree of repetitiveness and prolonged static nation of exposures to several physical factors such as force postures of the neck and shoulders. and repetitive work. An example would be holding a tool while working overhead. Poor muscle strength and low endurance have been shown in patients with neck-shoulder pain. Strength was affected in acute Insufficient evidence exists to make an association between patients,9,51 whereas endurance was impaired in chronic patients as shoulder tendinitis and exposure to segmental vibration. well.31,86,87 Other studies, however, failed to show a relationship Stenlund et al88 found such an association, but work with vibra- between neck and shoulder symptoms and strength and tion exposure also placed a large static load on shoulder muscles endurance.46 Indeed, the contrary was shown in a prospective so that the effects of forceful exertions could not be separated study; subjects with high muscle strength in shoulder elevation from it. seemed to be at a higher risk.40,45 A longitudinal study of motor assembly workers showed that low isometric strength of shoulder Because they are multifactorial in origin, shoulder MSDs are muscles was a risk factor for neck and shoulder pain.43 Hägg et al33 and may be associated with both occupational and nonoccupa- could not show significant relations between either EMG signs of tional factors whose relative contributions may be specific to fatigue during work or isometric strength with the development of particular disorders. The confounders for nonspecific shoulder muscular disorders during a 2-year follow-up. pain, for example, may differ from those for shoulder tendinitis. (Two of the most important confounders or effect modifiers for A few studies found certain personality traits to predispose to shoulder tendinitis are sport activities and age.) MSDs. Characterized by competitiveness, impatience, and a feeling of time urgency, the “type A” personality has been found Excessive contractions or fatigue can lead to tennis elbow, one to be associated with low back pain36,37,94 and with neck-shoulder of the most common occupational elbow problems.19 This is char- pain.24,33,83 acterized by intense pain of the lateral aspect of the elbow exacer- bated by grip and more use. Coonrad18 reported that the main Social factors problem is repetition, but it is multifactorial in origin. Allander3 reported a prevalence of one third in 15,000 subjects. In studies at Along with recognition of the importance of the physical load to certain occupational clinics, Dimberg20 found that 64% of all diag- MSDs, there is a growing awareness of their association with psy- nosed cases were related to work. Cyriax19 reported that only 8% chosocial factors and work environment.59,64 In a longitudinal of cases actually involved tennis. In a review, however, Maylack67 study, job satisfaction and relations with coworkers and supervi- reported that 50% of competitive tennis players suffer from at least sors were the strongest predictors for developing industrial back one episode of lateral epicondylitis. pain.7,8 Monotony, stress, low job satisfaction, lack of control, and low skill requirements characterized a typical light assembly Another elbow problem is cubital tunnel external compres- job where young males reported a high rate of back pain.57,62 In sion syndrome. As the ulnar nerve travels from the brachial a study of occupational drivers, the group that had the highest plexus to the hand, it is vulnerable to compression at certain incidence of both back pain and neck-shoulder pain reported the elbow flexion angles at a subcutaneous location behind the highest stress level and lowest job satisfaction.63 The same study humeral epicondyle (cubital tunnel). A common occupational found a strong relationship between back pain and neck-shoulder risk reported in drivers occurs where the elbow is rested on a pain also, indicating that individuals who are predisposed will hard surface for a long period of time.2 Mansukhani and develop any or several MSDs. Tola et al91 reported that moderate D’Souza66 reported unilateral ulnar neuropathy in diamond or poor job satisfaction and physical loading factors were signif- workers that was restricted to the arm holding the eyeglass for icant risk factors for neck and shoulder pain. Bergenudd et al7 inspecting the diamonds. found that women with a history of shoulder pain were less satisfied with their jobs than women who did not experience Individual factors pain. Among possible psychologic stresses at work, the combina- tion of high work demand and low control in particular seems to Not all workers performing similar and risky work tasks develop play an important role in the development of musculoskeletal MSDs, due to the obvious influence of individual factors on the complaints.36,37 exposure-effect relationship. The individual factors most fre- quently studied or controlled for are sex and age. Some studies PATHOMECHANISMS have shown that age affects the prevalence of MSDs,36,47,54,91,94 whereas others have shown no such influence.11 Workload Muscle strength and endurance influence the risk of neck and The common causative factor in MSDs is mechanical stress on upper limb disorders. With higher muscle strength, the muscle is musculoskeletal tissues. Normally, the tissues adapt to mechani- obviously less loaded than in the case of lower strength for the cal stress; that is, tissues strengthen with increased stress and same force exertion. Women in general have lower strength than men, in particular in the upper extremities, and older people are weaker than younger ones.69 Some studies, however, have shown that compared with men, women have longer muscle endurance

152 Chapter 5a ● Shoulder and elbow disorders weaken with less.90 When the stress exceeds the limit of adap- PREVENTION tion, pathologic changes may occur in the tissue. The risk of developing symptoms may also increase, however, when the According to Hagberg and Wegman,32 the occupationally related physical stress is very low.99 etiologic fraction of neck and upper extremity injuries is high, and therefore a relatively large number could be prevented. Hagberg and coworkers31,32 suggested three possible pathomech- Some studies have proved that intervention in working condi- anisms for muscle pain as a result of physical load: mechanical fail- tions can be successful,76 and rehabilitation of neck and upper ure, local ischemia, and energy metabolism disturbances. limb disorders often fails when not combined with such Mechanical failure of the muscles is typically the cause of the mus- improvements.23,75 Only a few studies have been able to describe cle soreness that occurs 24 to 48 hours after heavy physical exer- an exposure-effect relationship. For successful prevention, future tion. The pain is due to ruptures of the z-disks and outflow of studies of the quantification of physical exposure and the impor- metabolites from the muscle fibers, which directly or through tance of psychosocial factors are needed. edema activate pain receptors. 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154 Chapter 5a ● Shoulder and elbow disorders 88. Stenlund B, Goldie I, Hagberg M, Hogstedt C: Shoulder tendinitis and its relation 94. Westerling D, Jonsson BG: Pain from the neck and shoulder region and sick leave. to heavy manual work and exposure to vibration. Scand J Work Environ Health Scand J Soc Med 8:31-136, 1980. 19:43-49, 1993. 95. Westgaard RH, Aarås A: Postural muscle strain as a causal factor in the development 89. Takala EP, Viikari-Juntura E, Moneta G, Saarenmaa K, Kainanto K: Seasonal variation of work-related musculoskeletal illnesses. Appl Ergon 15:162-174, 1984. in neck and shoulder symptoms. Scand J Environ Health 18:257-261, 1992. 96. Westgaard RH, Bjørklund R: Generation of muscle tension additional to postural 90. Tipton CM, Vailas AC, Matthes RD: Experimental studies on the influence of physical load. Ergonomics 30:911-923, 1987. activity on ligaments, tendons and joints: a brief review. Acta Med Scand Suppl 711:157-168, 1986. 97. Winkel J: Why is there an increase in the occupational disorders? Nord Med 104:324-327, 1989 [In Swedish]. 91. Tola S, Riihimäki H, Videman T, Viikari-Juntura E, Hänninen K: Neck and shoulder symptoms among men in machine operating, dynamic physical work and sedentary 98. World Health Organization: Identification and control of work-related diseases. work. Scand J Work Environ Health 14:299-305, 1988. Report of a WHO Expert Committee. WHO Technical Report Series 714, 9, 1985. 92. Viikari-Juntura E: A life-long prospective study on the role of psychosocial factors in 99. World Health Organization: International Classification of Diseases. Manual of the neck-shoulder and low-back pain. Spine 16:1056-1061, 1991. International Statistical Classification of Diseases, Injuries, and Causes of Death. Vol 1. Geneva, 1977, WHO. 93. Waris P: Occupational cervicobrachial syndromes. A review. Scand J Work Environ Health 5(3):3-14, 1979.

CHAPTER 5b is implicated in a significant proportion of shoulder pathology, limitation of motion at the AC joint leads to minimal alterations Biomechanics of the in normal shoulder function.53 Like the SC joint, the AC joint Shoulder and Elbow possesses an intraarticular meniscus that enhances the contact Complex area between its two incongruent articular surfaces. The AC joint is stabilized by two sets of ligaments: the AC ligaments are David I. Pedowitz, David P. Beason, and Louis J. Soslowsky primarily condensations of the AC joint capsule, whereas the coracoclavicular ligaments include the more medial conoid and During physical activity, the forces acting on the shoulder and laterally based trapezoid ligaments. elbow have been estimated to be upward of several times body weight.1 Many workplace activities are known to involve heavy Scapulothoracic Articulation Not a true joint, the scapulotho- manual labor and chronic repetitive motion. Accordingly, the racic articulation represents the sliding and rotation between resultant forces and associated pain perceived at the shoulder the bony thorax and the scapula. The scapula lies flat on the and elbow can be greater at work due to the stress on the upper chest wall and is enveloped by muscle. The complex interaction extremity when larger loads are applied.25,51 Also of importance between the scapular and thoracic muscles affords stability and are work tasks involving postures nearing or exceeding the additional rotation for the scapula on the posterior thorax. This normal range of joint motion, stationary postures over extended in turn changes the orientation of the glenoid surface and signif- periods of time, highly repetitive motions, and excessive loading. icantly contributes to shoulder range of motion and function. A fundamental appreciation for the anatomy and biomechanics Because the scapulothoracic articulation is not a true joint, it has of the shoulder and elbow complexes serves as an excellent no discrete ligamentous attachments. foundation for better understanding these injuries. Glenohumeral Joint Often likened to a sideways golf ball on a THE SHOULDER tee, the glenohumeral articulation allows more range of motion than that of any other major joint in the body. The joint itself Anatomic considerations is composed of the head of the humerus laterally, which articu- lates with the glenoid of the scapula medially. The glenoid is Because the shoulder is the primary conduit through which forces shaped like a pear, being broader distally and narrow proximally. travel from the hand and elbow to the axial skeleton, a thorough It is covered in cartilage that is thin at the center and thickens understanding of the anatomy is paramount when considering its more peripherally. Along the outer edge of the glenoid is a rim function and relation to patients’ symptoms. The shoulder com- of thick fibrous soft tissue, the glenoid labrum, which deepens plex is essentially composed of three bones, the clavicle, the the articular surface and also acts as the origin for the long head scapula, and the proximal humerus, which participate in four prin- of biceps (LHB) tendon and the glenohumeral ligaments. cipal articulations (Fig. 5b.1). Through these joints, the shoulder is acted on by nearly 30 different muscles that either affect the shoul- The articular surface of the humerus extends medially from der itself or connect the upper extremity to the spine and the chest the anatomic neck to form approximately one third of an irreg- wall. The following anatomic descriptions are meant to introduce ularly shaped sphere. Unlike the more static midline structures the critical concepts of shoulder form and function. on the chest wall that lie in the standard anteroposterior plane, the shoulder lies in the scapular plane. Viewed from above, Articulations the scapula is anteverted 30 degrees to lie flat on the curved Sternoclavicular Joint The most medial articulation in the posterior chest wall. This placement is balanced by a 30-degree retroversion of the humeral head. shoulder complex, the sternoclavicular (SC) joint is comprised of the medial clavicle and the proximal part of the sternum, The joint capsule of the shoulder is a thin redundant sleeve the manubrium. This joint serves as a strut connecting the axial of fibrous tissue that extends from the glenoid neck to the skeleton to the upper extremity. The congruity of the articulation anatomic neck and variable areas of the proximal shaft of the is enhanced by an intraarticular disk, which also confers some humerus. The primary ligamentous structures at the glenohumeral stability and cushioning for the two bony surfaces. The joint has joint are the coracohumeral and the three glenohumeral ligaments some limited motion in nearly all directions that is stabilized by (Fig. 5b.2). The coracohumeral ligament (CHL) arises from the surrounding tough ligamentous structures. coracoid process and attaches to the greater and lesser tuberosi- ties of the humerus. The glenohumeral ligaments are essentially Acromioclavicular Joint Similarly to the SC joint, the acromio- condensations of capsule extending from the rim of the anterior clavicular (AC) joint is a conduit for forces from the distal upper articular surface of the glenoid to the head of the humerus. They extremity to the central axis of the body. Although the acromion provide significant stability to the joint and appear as discrete structures when viewed arthroscopically. The superior gleno- humeral ligament extends from the tubercle of the glenoid ante- rior to the LHB tendon origin and inserts at the proximal tip of the lesser tuberosity. The middle glenohumeral ligament spans the distance between the anterior superior labrum and supragle- noid tubercle to the lesser tuberosity, where it blends with the subscapularis tendon. The strongest and most important of the glenohumeral ligaments, the inferior glenohumeral ligament

156 Chapter 5b ● Biomechanics of the shoulder and elbow complex Clavicle (cut) Figure 5b.1 Bones of the shoulder region, anterior Coracoid process (A) and posterior (B) views. Acromion Supraglenoid Neck tubercle Anatomical neck Subscapular fossa Greater tubercle Infragneloid tubercule Lesser tubercle Glenoid Surgical Neck cavity of scapula Intertubercylar groove Deltoid tuberosity Head of Scapula Humerus Humerus {Condyles Medial Lateral Radial fossa Lateral epicondyle Capitulum Trochlea Coronoid fossa A Medial epicondyle Supraspinatus fossa Clavicle (cut) Spine Coracoid process Neck Acromion Infraspinatus fossa Greater tubercle Head of humerus Anatomical neck Surgical neck Infraglenoid tubercle Deltoid tuberosity Scapula Humerus Olecranon fossa Lateral epicondyle Trochlea Groove for ulnar nerve B Medial epicondyle

Chapter 5b ● The shoulder 157 Anterior view Clavicle Acromion Trapezoid Coraco- ligament clavicular Coracoacromial ligament Conoid ligament ligament Supraspinatus tendon (cut) Coracohumeral ligament Coracoid process Greater tubercle and Lesser tubercle of humerus Transverse ligament of humerus Subscapularis tendon Biceps brachii tendon (long Head) Capsular ligaments Figure 5b.2 Capsular and ligamentous structures of the shoulder, anterior view. (IGHL), arises from most of the anterior glenoid labrum and leading edge of the coracoacromial ligament can impinge against inserts on the inferior margin of the humeral articular surface, the rotator cuff and LHB tendons. around the anatomic neck of the humerus. Muscles Another important structure at the glenohumeral articulation is the coracoacromial arch, the osseoligamentous roof of the The largest and most appreciable muscle in the shoulder region is shoulder region formed by the coracoid process, the coracoacro- the deltoid, which defines the thick rounded contour of the healthy mial ligament, and the acromion of the scapula. Beneath the shoulder. The muscle consists of three major sections—anterior, coracoacromial arch is the subacromial space, the rotator cuff, middle, and posterior—that are variably active in different aspects the LHB tendon, and the head of the humerus. In varying degrees of shoulder motion. Overall, the deltoid is active in all forms of ele- of shoulder pathology, the undersurface of the acromion or vation.13 Table 5b.1 describes the muscles of the shoulder. Table 5b.1 Muscles of the shoulder Muscle Origin Insertion Innervation Action Deltoid Lateral one third of clavicle, acromion, Deltoid tuberosity of humerus Axillary n. (C5-C6) Shoulder flexion, extension, and spine of scapula Musculocutaneous n. (C5-C6) abduction, some internal/ Tuberosity of the radius and external rotation Biceps Short head: coracoid process of forearm via bicipital Subscapularis scapula aponeurosis Forearm flexion, supination of flexed forearm Long head: supraglenoid tubercle of Lesser tuberosity of humerus scapula Upper and lower subscapular nn. Internally rotates and adducts Greater tuberosity of humerus Subscapular fossa of scapula Greater tuberosity of humerus Greater tuberosity of humerus Medial lip of intertubercular (C5-C7) humerus Supraspinatus Supraspinous fossa of scapula groove of humerus Suprascapular n. (C4-C6) Abducts humerus Infraspinatus Infraspinous fossa of scapula Lateral one third of clavicle, Teres minor Superior border of lateral scapula Suprascapular n. (C5-C6) Externally rotates humerus Teres major Inferior border of lateral scapula acromion, and spine of scapula Axillary n. (C5-C6) Externally rotates humerus Floor of intertubercular groove of humerus Lower subscapular n. (C6-C7) Adducts and internally rotates Anteromedial border of the scapula humerus Trapezius Spinous processes of C7-T12 Spinal accessory n. (CN-XI) Elevates, retracts, and rotates vertebrae scapula Latissimus dorsi Spinous processes of T7-T12 vertebrae Thoracodorsal n. (C6-C8) Extends, adducts, and internally Serratus anterior and iliac crest Long thoracic n. (C5-C7) rotates humerus Lateral surface of ribs 1-8 Protracts and rotates scapula medially n., nerve; nn., nerves.