Copyright © 2005 by F. A. Davis. with single-leg extension in the hands and knees Chapter 4: The Vertebral Column ■ 185 position (see Fig. 4-65B). The right erector spinae and contralateral abdominal muscles were activated ▲ Figure 4-65 ■ A. Single-leg extension in the quadriped posi- during single right-leg extension to maintain a neu- tion creates low compression forces at the L4/L5 segment. B. Raising tral pelvis and spine posture and to balance internal the opposite leg and arm simultaneously increases compression moments and lateral shear forces. forces at the L4/L5 segment by 1000 N and upper erector spinae muscle activity by 30% in comparison with single-leg raising. The authors recommended that only single-leg extension exercises be performed because the lum- the mechanisms involved in lifting and to determine bar posture is more neutral and the compression the best method of lifting so that back injuries can be forces are relatively low (approximately 2500 N). prevented. A great deal of focus has been on the squat They further recommended that the exercise in versus stoop lift (Fig. 4-66). During a stoop lift, trunk which the subject raises the upper body and legs flexion is achieved primarily by thoracolumbar flexion, from a prone lying position never be prescribed for and there is little to no knee flexion. During a squat lift, anyone at risk for low back injury or reinjury to the the spine remains as erect as possible and trunk flexion lumbar spine, because during this exercise, lumbar is achieved primarily by hip and knee flexion. compression forces of up to 6000 N are incurred. The extremely high compression forces are a result Continuing Exploration: Squat Lifting versus of bilateral muscle activity when the spine is hyper- Stoop Lifting extended. In this posture, the facets are subjected to Controversy persists in the literature as to whether high loads, and the interspinous ligament is in dan- there is biomechanical evidence in support of advo- ger of being crushed.117 cating the squat lifting technique over the stoop lift- ing technique to prevent low back pain. A review by Trunk sit-ups and curl-ups are often performed as a method of abdominal strengthening. McGill measured compression forces during these tasks, with both bent knees and straight knees. He found the compression forces to be approximately 3300 N, without much variation between the types.118 McGill suggested that. given these large compressive loads, most people, let alone those who have sustained injury to this area, should not perform sit-ups of any type.26 ■ Injury Prevention with Lifting Tasks: Squat Lift versus Stoop Lift The prevalence of back problems in the general popu- lation and the difficulties of resolving these problems has generated a great deal of research both to explain AB Squat lift Stoop lift ᭣ Figure 4-66 ■ Squat (A) ver- sus stoop (B) lift.
Copyright © 2005 by F. A. Davis. 186 ■ Section 2: Axial Skeletal Joint Complexes much debate. Bartelink suggested that an increased IAP decreases spinal compressive loads by pushing van Dieen and coworkers in 1999 concluded that the up on the rib cage. The author reasoned that closing literature does not support advocating squat lifting the glottis and bearing down exerts a force down- over stoop lifting.119 However, The National Health ward on the pelvic floor and upward on the dia- Service Centre for Reviews and Dissemination cau- phragm, which puts tension through the lumbar tioned that the review by van Dieen and coworkers region and decreases some compression by produc- contained methodological flaws that affected the ing an extensor moment.126 authors’ conclusions.120 The points that follow appear to support the use of the squat lift. McGill and Norman127 challenged this theory by arguing that the large compressive loads caused by The extensor muscles are at a disadvantage in contraction of the abdominal muscles negate any the fully flexed position of the spine because of potential unloading affect and that a net increase in shortened moment arms in this position, a change in compression through the lumbar spine would result the line of pull, and the possibility of passive insuffi- from increased IAP. Cholewicki and colleagues128 ciency resulting from the elongated state of the mus- suggested that the increase in IAP has more to do cles. In a neutral lumbar spine posture, the deep with providing stability to the lumbar region and less layer of the erector spinae is capable of producing to do with generating extensor torque. McGill and posterior shear, which will help to offset the tremen- Norman agreed with Cholewicki and coworkers that dous amounts of anterior shear that occur with the role of the increased IAP is to stiffen the trunk trunk flexion, particularly if the person is carrying an and prevent tissue strain or failure from buckling of additional load.26,114 The diminished capacity of the the spine.127,128 extensors to generate torque and to counteract the anterior shear forces in the forward flexed position Hodges and colleagues129 provided some recent are important reasons why stoop lifting is discour- evidence to support the theory that an increased IAP aged.26,114 produces an extensor torque; however, they created the increase in IAP without abdominal contraction Another factor involved is intradiskal pressures. by stimulating the phrenic nerve. It appears that fur- Wilke and colleagues updated the classic works of ther studies are needed to delineate the role of the Nachemson, studying in vivo measurements of inter- increase in IAP during lifting tasks. vertebral disk pressure.121 Both Wilke and Nachem- son found that intervertebral disk pressures were C a s e A p p l i c a t i o n 4 - 9 : Instruction for Proper substantially higher when a load was held in a Lifting Techniques stooped position than in a squat position.121,122 An important aspect of rehabilitation for Malik will be to In contrast, there is some evidence that squat teach him appropriate bending and lifting mechanics. lifting results in higher compression forces than One of his primary complaints is pain with lifting from a does stoop lifting. However, damaging shear forces stooped position. This position will cause greater ante- were two to four times higher for the stoop lift than rior shear forces through the lumbar region and may be for the squat lift.119,123 Although excessive compres- responsible for his pain. In treatment, therefore, he sive loads can and will produce damage, the spine is should be taught how to bend and lift in the squat posi- better designed to tolerate compressive loads in tion, keeping a neutral lumbar spine position. This will comparison with shear forces. Preventing these remove some strain from the deep erector spinae and excessive shear forces, therefore, is critical in pre- allow them to participate in control of the anterior shear venting injury.114 forces. In addition, it may be necessary in the early stages of rehabilitation to keep Malik from using Other, less controversial critical factors in lifting in increased IAP when he lifts, because the added com- any posture appear to be the distance from the body to pressive forces may be further irritating the interverte- the object to be lifted,74 the velocity of the lift, and the bral disks, which could be producing pain. degree of lumbar flexion.124 The farther away the load is from the body, the greater is the gravitational Muscles of the Pelvic Floor moment acting on the vertebral column. Greater mus- cle activity is required to perform the lift, and conse- ■ Structure quently greater pressure is created in the disk. The higher the velocity of the lift is, the greater is the Although the levator ani and coccygeus muscles nei- amount of weight that can be lifted, but the higher is ther play a major supporting role for the vertebral col- the load on the lumbar disks. The relative spinal load umn nor produce movement of the column, these and applied erector spinae force increase significantly muscles are mentioned here because of their proximity with the velocity of trunk extension.125 to the column and possible influence on the linkages that form the pelvis. The levator ani muscles comprise Continuing Exploration: Role of Intra-abdominal two distinct parts, the iliococcygeus and the pubococ- Pressure (IAP) in Lifting cygeus, which help to form the floor of the pelvis and separate the pelvic cavity from the perineum. The left An increase in IAP is frequently demonstrated dur- ing lifting tasks. What role the increase in IAP plays as a mechanism of support to the lumbopelvic region during lifting tasks has been the subject of
Copyright © 2005 by F. A. Davis. and right broad muscle sheets of the levator ani form Chapter 4: The Vertebral Column ■ 187 the major portion of the floor of the pelvis. The medial borders of the right and left muscles are separated by amount and form of the trabeculae. The numbers of the visceral outlet, through which pass the urethra, both horizontal and vertical trabeculae decrease with vagina (in the female), and anorectum. The pubococ- age, and the horizontal trabeculae become significantly cygeal part of the muscle arises from the posterior thinner.130 This loss can decrease the loads that the ver- aspect of the pubis and has attachments to the sphinc- tebrae are able to withstand before failure. ter, urethra, walls of the vagina (in the female), and the pineal body and rectum (in both genders). The ilio- Each of the structures of the intervertebral disk coccygeal portion, which arises from the obturator fas- undergo changes that include loss of the amount of cia, is thin. Its fibers blend with the fibers of the proteoglycans and change in the specific type of pro- anococcygeal ligament, form a raphe, and attach to the teoglycan, with resultant loss of water content. In addi- last two coccygeal segments. The coccygeus muscle tion, there is an increase of collagen in these structures arises from the spine of the ischium and attaches to the and loss of elastin. This results in a loss of the ability for coccyx and lower portion of the sacrum. The gluteal the disk to transfer loads from one vertebra to another surface of the muscle blends with the sacrospinous lig- as the swelling ability of the nucleus decreases. The ament (Fig. 4-67). overall disk height will also decrease somewhat. ■ Function The vascularization of the disk also changes. In Voluntary contractions of the levator ani muscles help utero, blood vessels can be demonstrated within the constrict the openings in the pelvic floor (urethra and fibers of the anulus fibrosus.131 By the end of the sec- anus) and prevent unwanted micturition and defeca- ond year of life, these have predominantly degener- tion (stress incontinence). Involuntary contractions of ated. Thus, the disk relies on the diffusion of nutrients these muscles occur during coughing or holding one’s through the vertebral end plate. The vertebral end breath when the IAP is raised. In women, these muscles plate, with aging, gradually becomes more collagenous, surround the vagina and help to support the uterus. and the process of diffusion is hindered. The fibers of During pregnancy the muscles can be stretched or trau- the anulus fibrosus in the cervical spine of adults nor- matized, which can result in stress incontinence when- mally demonstrate lateral fissures that subdivide the ever the IAP is raised. In men, damage to these muscles disk into two halves at the uncovertebral joints. These may occur after prostate surgery. The coccygeus muscle fissures can first be observed in children at approxi- assists the levator ani in supporting the pelvic viscera mately 9 years of age.131 After formation of these fis- and maintaining IAP. sures, joint pseudocapsules develop with vascularized synovial folds. The formation of these fissures appears Effects of Aging to be load-related and is located predominantly in the regions of C3 to C5. Age-Related Changes With large and/or repetitive loads, further changes Over the life span, the vertebral column is exposed to occur in the disks. The disks demonstrate a dramatic recurrent loads that change the morphology of the col- decrease in their elasticity and proteoglycans.131,132 umn. However, normal age-related changes also occur Eventually, the intervertebral disk will become so dry in the structures of the vertebral column. that it begins to crumble. In the lumbar region, the inner layers of the anulus fibrosus begin to buckle out- The vertebral bone undergoes changes in the ward, and the lamellae separate. Fissures and tears can occur within the anular fibers, which can decrease the ▲ Figure 4-67 ■ Muscles of the pelvic floor. ability of the disk to provide stiffness during move- ment.132 The vertebral end plates may become ossified. The adjacent spongy bone of the vertebral body can begin to sclerose. On occasion, blood vessels grow into the disks and trigger ossification.131 The disk can pro- lapse or protrude as a result of the pressure of the nucleus and the lack of ability of the anulus fibrosus to sustain it. Schmorl’s nodes are formed when the nuclear material prolapses through the vertebral end plate and into the cancellous bone of the vertebra. This material may cause an autoimmune response when it comes in contact with the blood supply in the cancellous bone.110 This is typically labeled degenerative disk disease. In this case of degenerative disk disease, there is a more substantial loss of disk height, which causes all lig- aments to be placed on slack. The ligamentous pre- stress normally provided by the ligamentum flavum will decrease, which in turn will impair spinal stiffness. This can also allow the ligament to buckle on itself with movement, potentially compressing the spinal cord. In addition, the ligamentum flavum begins to calcify with age, and this occasionally leads to ossification, which can also potentially cause compression of the spinal
Copyright © 2005 by F. A. Davis. 188 ■ Section 2: Axial Skeletal Joint Complexes CONCEPT CORNERSTONE 4-6: Osteophyte Formation nerve in the vicinity of the zygapophyseal joints or the Clinicians should remember the frequency of osteophyte formation spinal cord within the canal.133,134 at the uncinate processes and subsequent lateral bending limita- tions when examining cervical ROM. Restoration of lateral bending The zygapophyseal joints can also demonstrate age- motion is often not a realistic expectation. related changes and eventual degeneration. Some authors have argued that these changes in the Summary zygapophyseal joints must be secondary to disk degen- eration, as a substantial amount of weight-bearing In summary, it is extremely important to understand the through these joints must occur to cause deterioration. normal structure and function, including normal variability, This increase in weight-bearing may be due to the loss of the vertebral column in order to understand the struc- of disk height. However, this is not always the case.131 tures at risk for injury and the best ways to treat people There have been descriptions of degenerative zygapo- with dysfunction. Injury or failure occurs when the applied physeal joints without disk degeneration. The mecha- load exceeds the strength of a particular tissue. Repetitive nism of this is not as well understood. If, however, the strain causes injury by either the repeated application disks degenerate and a substantive decrease in height of a relatively low load or by application of a sustained occurs, what follows is hypermobility as a result of slack- load for a long duration (prolonged sitting or stooped ened capsules and longitudinal ligaments. The vertebra posture). may also slip forward or backward on the vertebra below (listhesis or retrolisthesis). There will be excessive shear The effects of an injury, aging, disease, or development forces generated, and the zygapophyseal joints will also deficit on the vertebral column may be analyzed by taking become subject to more load-bearing. the following points into consideration: The result of these changes becomes the same as 1. the normal function that the affected structure is with what happens to the larger joints of the extremi- designed to serve ties: damage of the cartilage, including fissures and cysts, and osteophyte formation. These changes can 2. the stresses that are present during normal situations lead to localized pain or pressure on spinal nerves or 3. the anatomic relationship of the structure to adjacent the central canal or, in the cervical region, compression of the vertebral artery in the transverse foramen.131 structures 4. the functional relationship of the structure to other The joints of Luschka, or uncovertebral joints, are frequent sites for age-related and degenerative changes. structures Osteophytes on the uncinate processes occur predomi- nantly in the lower segments C5/C6 or C6/C7. The motion of lateral bending becomes extremely limited when these osteophytes occur. Study Questions 1. Which region of the vertebral column is most flexible? Explain why this region has greater flexi- bility. 2. Describe the relationship between the zygapophyseal joints and the interbody joints. 3. What is the zygapophyseal facet orientation in the lumbar region? How does this orientation dif- fer from that of other regions? How does the orientation in the lumbar region affect motion in that region? 4. Describe the relative strength of the longitudinal ligaments in the lumbar region. How does this differ from the other regions? Are some structures more susceptible to injury in this region on the basis of this variation? 5. Which structures would be affected if a person has an increased anterior convexity in the lumbar area? Describe the type of stress that would occur, where it would occur, and how it would affect different structures. 6. Describe the function of the intervertebral disk during motion and in weight-bearing. 7. Describe the differences in structure between the cervical and lumbar intervertebral disks. 8. Identify the factors that limit rotation in the lumbar spine. Explain how the limitations occur. 9. Which muscles cause extension of the lumbar spine? In which position of the spine are they most effective? 10. Describe the forces that act on the spine during motion and at rest. 11. Explain how “creep” may adversely affect the stability of the vertebral column. 12. Describe how muscles and ligaments interact to provide stability for the vertebral column. 13. What role has been attributed to the thoracolumbar fascia in stability of the lumbopelvic region? 14. Describe the dynamic and static restraints to anterior shear in the lumbar region. 15. Describe the dynamic restraints to anterior shear in the cervical region.
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Spine 15:11, Identification of alternative paths of loading. 1990. Spine 19:2667, 1994. 109. Pidcoe P, Mayhew T: Mechanics and pathome- chanics of the cervical musculature. In Oatis C 89. Khoo BCC, Goh JC, Lee JM, et al.: A comparison (ed): Kinesiology: The Mechanics & Pathome- of lumbosacral loads during static and dynamic chanics of Human Movement. Philadelphia, activities. Australas Phys Eng Sci Med 17:55, 1994. Lippincott Williams & Wilkins, 2004. 110. Porterfield J, DeRosa C: Mechanical Low Back 90. Bowen V, Cassidy JD: Macroscopic and micro- Pain: Perspectives in Functional Anatomy, 2nd ed. scopic anatomy of the sacroiliac joint from embry- Philadelphia, WB Saunders, 1998. onic life until the eighth decade. Spine 6:620, 111. Daggfeldt K, Huang QM, Thorstensson A: The vis- 1981. ible human anatomy of the lumbar erector spinae. Spine 25:2719, 2000. 91. Mierau DR, Cassidy JD, Hamin T, et al.: Sacroiliac 112. Bustami FM: A new description of the lumbar joint dysfunction and low back pain in school erector spinae muscle in man. J Anat 144:81, aged children. J Manipulative Physiol Ther 7:81, 1986. 1994. 92. Walker JM: The sacroiliac joint: A critical review. Phys Ther 72:903, 1992. 93. Salsabili N, Valojerdy MR, Hogg DA: Variations in thickness of articular cartilage in the human sacroiliac joint. Clin Anat 8:388,1995. 94. Cassidy JD: The pathoanatomy and clinical signif- icance of the sacroiliac joints. J Manipulative Physiol Ther 15:41, 1992. 95. McLauchlan GJ, Gardner DL: Sacral and iliac articular cartilage thickness and cellularity: Relationship to subchondral bone end-plate thick-
Copyright © 2005 by F. A. Davis. 192 ■ Section 2: Axial Skeletal Joint Complexes 124. Dolan P, Mannion AF, Adams MA: Passive tissues help the muscles to generate extensor moments 113. Bojadsen TWA, Silva ES, Rodrigues AJ, et al.: Com- during lifting. J Biomech 27:1077, 1994. parative study of Mm. Multifidi in lumbar and tho- racic spine. J Electromyogr Kinesiol 10:143, 2000. 125. Granata KP, Marras WS: The influence of trunk muscle coactivity on dynamic spinal loads. Spine 114. McGill S: Mechanics and pathomechanics of mus- 20:913,1995. cles acting on the lumbar spine. In Oatis C (ed): Kinesiology: The Mechanics & Pathomechanics of 126. Bartelink DL: The role of abdominal pressure in Human Movement. Philadelphia, Lippincott relieving the pressure on the lumbar interverte- Williams & Wilkins, 2004. bral disc. J Bone Joint Surg Br 39:718. 115. Richardson CA, Snijders CJ, Hides JA, et al.: The 127. McGill S, Norman R: Reassessment of the role of relation between the transversus abdominis mus- intra-abdominal pressure in spinal compression. cles, sacroiliac joint mechanics, and low back Ergonomics 30:1565, 1987. pain. Spine 27:399, 2002. 128. Cholewicki J, Juluru K, McGill SM, et al.: Intra- 116. Cholewicki J, Panjabi MM, Khachatryan A: abdominal pressure mechanism for stabilizing the Stabilizing function of trunk flexor-extensor mus- lumbar spine. J Biomech 32:13, 1999. cles around a neutral spine posture. Spine 22: 2207, 1997. 129. Hodges P, Cresswell AG, Daggfeldt K, et al.: In vivo measurement of the effect of intra-abdominal 117. Callaghan JP, Gunning JL, McGill SM: The rela- pressure on the human spine. J Biomech 34:347, tionship between lumbar spine load and muscle 2001. activity during extensor exercises. Phys Ther 78:8, 1998. 130. Thomsen JS, Ebbesen EN, Mosekilde LI: Age- related differences between thinning of horizon- 118. McGill SM: Low back exercises: Evidence for tal and vertical trabeculae in human lumbar bone improving exercise regimens. Phys Ther 78:754, as assessed by a new computerized method. Bone 1998. 31:136, 2002. 119. van Dieen J, Hoozemans MJ, Toussaint HM: Stoop 131. Prescher A: Anatomy and pathology of the aging or squat: A review of biomechanical studies on lift- spine. Eur J Radiol 27:181, 1998. ing technique. Clin Biomech (Bristol, Avon) 14: 685, 1999. 132. Thompson R, Pearcy MJ, Downing KJ, et al.: Disc lesions and the mechanics of the intervertebral 120. National Health Service Centre for Reviews and joint complex. Spine 25:3026, 2000. Dissemination: Stoop or squat. Database of Abstracts of Reviews of Effectiveness, Issue 3, 2003. 133. Maigne JY, Ayral X, Guerin-Surville H: Frequency and size of ossifications in the caudal attachments 121. Wilke HJ, Neef P, Caimi M, et al.: New in vivo of the ligamentum flavum of the thoracic spine. measurements of pressures in the intervertebral Role of rotatory strains in their development. An disc in daily life. Spine 24(8):755, 1999. anatomic study of 121 spines. Surg Radiol Anat 14:119, 1992. 122. Nachemson A: The load on lumbar discs in dif- ferent positions of the body. Clin Orthop 45:107, 134. Mak K, Mak KL, Gwi-Mak E: Ossification of the lig- 1966. amentum flavum in the cervicothoracic junction: case report on ossification found on both sides of 123. Potvin JR, McGill SM, Norman RW: Trunk muscle the lamina. Spine 27:E11, 2002. and lumbar ligament contributions to dynamic lifts with varying degrees of trunk flexion. Spine 16:1099, 1991.
Copyright © 2005 by F. A. Davis. 5 Chapter The Thorax and Chest Wall Julie Starr, PT, MS, CCS, Diane Dalton, PT, MS, OCS Introduction Coordination and Integration of Ventilatory Motions General Structure and Function Rib Cage Developmental Aspects of Structure and Function Articulations of the Rib Cage Differences Associated with the Neonate Kinematics of the Ribs and Manubriosternum Differences Associated with the Elderly Muscles Associated with the Rib Cage Primary Muscles of Ventilation Pathological Changes in Structure and Function Accessory Muscles of Ventilation Chronic Obstructive Pulmonary Disease Introduction range of motion of the chest cage and the spine and, therefore, decrease ventilation abilities.4 The coupling The thorax, consisting of the thoracic vertebrae, the and interaction of the bony thorax and the ventilatory ribs, and the sternum (Fig. 5-1A and B), has several muscles and their relationship to ventilation will be the important functions. The thorax provides a base for the focus of this chapter. attachment of muscles of the upper extremities, the head and neck, the vertebral column, and the pelvis. 5-1 Patient Case The thorax also forms protection for the heart, lungs, and viscera. Therefore, there needs to be a certain Mary Nasser is a 12-year-old who is trying out for her town’s ten- amount of inherent stability to the thorax. Probably the nis team. This is the first time she has ever really played tennis most important function of the chest wall is its role in beyond lessons in childhood. She began to have complaints of ventilation. The process of ventilation depends on the shortness of breath with portions of practice that involved a high mobility of the bony rib thorax and the ability of the level of exertion. She saw her primary care physician, who picked muscles of ventilation to move it.1,2 up evidence of a scoliosis (curvature of the spine) in her initial screening. Spine radiographs were done, and Mary was diag- Function, especially ventilatory function, can be nosed with an idiopathic right thoracic scoliosis, with a 40Њ curve. affected when pathology interferes with the structure of A medical workup was negative for an acute pulmonary process. the bony thorax. For example, scoliosis is a pathologic Mary was referred to an orthopedic surgeon and to physical ther- lateral curvature of the spine, frequently associated apy for management of the scoliosis and shortness of breath. with rotation of the vertebrae.3 A right thoracic scolio- sis (named by the side of the convexity of the curve) General Structure results in left lateral flexion of the thoracic spine (Fig. and Function 5-2A). The coupled rotation in a typical right thoracic scoliosis causes the bodies of the vertebrae to rotate to Rib Cage the right and the spinous processes to rotate left. The right transverse processes of the vertebrae rotate poste- The rib cage is a closed chain that involves many joints riorly, carrying the ribs with them (see Fig. 5-2B). This and muscles. The anterior border of the rib cage is the is the mechanism causing the classic posterior rib sternum, the lateral borders are the ribs, and the pos- hump of scoliosis. On the concave side of the scoliotic terior border is formed by the thoracic vertebrae. The curve, the effects are just the opposite. The transverse superior border of the rib cage is formed by the jugular processes of the vertebrae move anteriorly, bringing the articulated ribs forward. The rib distortion that results from the vertebral rotation is evident bilaterally in Figure 5-2A. These musculoskeletal abnormalities limit 193
Copyright © 2005 by F. A. Davis. 1st rib 194 ■ Section 2: Axial Skeletal Joint Complexes A Scapula Manubrium Sternal angle Costochondral joint Body of sternum Costal cartilage Xiphoid process B 1st thoracic vertebra and rib Clavicle Acromion of scapula Angle of 7th rib ▲ Figure 5-1 ■ Anterior (A) and posterior (B) views of the thorax are shown, including its component parts: the sternum, 12 pairs of ribs and their costocartilages, and the thoracic vertebrae.
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 195 Sternum AB Right ▲ Figure 5-2 ■ A. A right thoracic scoliosis (named by the side of the convexity) of 52Њ shows the evident rib distortion that results from accompanying rotation of the involved vertebrae. There is also a lumbar curve of 32Њ. B. The bodies of the thoracic vertebrae in scoliosis typi- cally rotate to the right, resulting in posterior displacement of the right transverse process and the attached right rib, as well as anterior dis- placement of the opposite transverse process and left rib. notch of the sternum, by the superior borders of the xiphoid process (Fig. 5-3). The manubrium and the first costocartilages, and by the first ribs and their con- body form a dorsally concave angle of approximately tiguous first thoracic vertebra. The inferior border of 160Њ. The xiphoid process often angles dorsally from the rib cage is formed by the xiphoid process, the the body of the sternum and may be difficult to palpate. shared costocartilage of ribs 6 through 10, the inferior portions of the 11th and 12th ribs, and the 12th tho- There are 12 thoracic vertebrae that make up the racic vertebra (see Fig. 5-1). posterior aspect of the rib cage. One of the unique aspects of the typical thoracic vertebra is that the verte- The sternum is an osseous protective plate for the bral body and transverse processes have six costal artic- heart and is composed of the manubrium, body, and ulating surfaces, four on the body (a superior and an inferior costal facet, or demifacet, on each side) and Jugular one costal facet on each transverse process (Fig. 5-4). notch The rib cage also includes 12 pairs of ribs. The ribs are curved flat bones that gradually increase in length from rib 1 to rib 7 and then decrease in length again from rib 8 to rib 12.5 The posteriorly located head of each rib Manubrium Costal cartilage Transverse Superior costal facet of 1st rib costal facet 2nd costal notch Manubriosternal joint 4th costal Body of notch sternum 7th costal Xyphoid Inferior costal facet notch process ▲ Figure 5-4 ■ The costal facets on the typical thoracic verte- ▲ Figure 5-3 ■ The sternum is composed of the manubrium, brae are found on the superior and inferior aspects of the posterior the body of the sternum, and the xiphoid process. The costal notches body and the anterior transverse processes. for the chondrosternal joints are also evident in this anterior view.
Copyright © 2005 by F. A. Davis. 196 ■ Section 2: Axial Skeletal Joint Complexes Costal Superior Demifacets tubercle facet of head Inner surface Inferior of rib facet of head Outer surface 8th rib ᭣ Figure 5-5 ■ The typical rib (ribs 2 through 9) of rib is a curved flat bone. The posteriorly located head of Site of articulation the rib has superior and inferior facets that are sepa- with costal cartilage rated by a ridge called the crest of the head. The supe- rior and inferior facets (also known as demifacets) articulate, respectively, with the superior and inferior costal facets on the body of the vertebrae; the facet on the costal tubercle articulates with the transverse costal facet on the transverse process of the vertebra; the rib articulates anteriorly with costal cartilages. articulates with thoracic vertebral bodies; and the costal because they have no anterior attachment to the ster- tubercles of ribs 1 to 10 also articulate with the trans- num.5 verse processes of a thoracic vertebra (Fig. 5-5). Ante- riorly, ribs 1 to 10 have a costocartilage that join them ■ Articulations of the Rib Cage either directly or indirectly to the sternum through the costal cartilages (Fig. 5-6). The first through the sev- The articulations that join the bones of the rib cage enth ribs are classified as vertebrosternal (or “true”) include the manubriosternal (MS), xiphisternal (XS), ribs because each rib, through its costocartilage, costovertebral (CV), costotransverse (CT), costochon- attaches directly to the sternum. The costocartilage dral (CC), chondrosternal (CS), and the interchondral of the 8th through 10th ribs articulates with the costo- joints. cartilages of the superior rib, indirectly articulating with the sternum through rib 7. These ribs are classified Manubriosternal and Xiphisternal Joints as vertebrochondral (or “false”) ribs. The 11th and 12th ribs are called vertebral (or “floating”) ribs The manubrium and the body of the sternum articulate at the MS joint (see Fig. 5–3). This joint is also known ▲ Figure 5-6 ■ In this anterior view of the rib cage, the ribs as the sternal angle or the angle of Louis and is readily articulate with the costal cartilages. The ribs join the costal cartilages palpable.1,6 The MS joint is a synchondrosis. The MS at the costochondral joints. The costal cartilages of the first through joint has a fibrocartilaginous disk between the hyaline the seventh ribs articulate directly with the sternum through the cartilage–covered articulating ends of the manubrium chondrosternal joints. The costal cartilages of the 8th through the and sternum—structurally similar to the symphysis 10th ribs articulate indirectly with the sternum through the costal car- pubis of the pelvis. Ossification of the MS joint occurs tilages of the adjacent superior rib at the interchondral joints. in elderly persons.6,7 The xiphoid process joins the infe- rior aspect of the sternal body at the XS joint. The XS joint is also a synchondrosis that tends to ossify by 40 to 50 years of age.8 Costovertebral Joints The typical CV joint is a synovial joint formed by the head of the rib, two adjacent vertebral bodies, and the interposed intervertebral disk. Ribs 2 to 9 have typical CV joints, inasmuch as the heads of these ribs each have two articular facets, or so-called demifacets6,9 (see Fig. 5-5). The demifacets are separated by a ridge called the crest of the head of the rib. The small, oval, and slightly convex demifacets of the ribs are called the superior and inferior costovertebral facets. Adjacent thoracic vertebrae have facets corresponding to those of the 9 ribs that articulates with them. The head of each of the second through ninth ribs articulates with an infe- rior facet on the superior of the two adjacent vertebrae and with a superior facet on the inferior of the two
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 197 ᭣ Figure 5-7 ■ A lateral view of the CV joints and liga- ments. The three bands of the radiate ligament reinforce the CV joints. The superior and inferior bands of the radiate liga- ment attach to the joint capsule (removed) and to the superior and inferior vertebral bodies, respectively. The intermediate band attaches to the intervertebral disk. The middle CV joint is shown with the radiate ligament bands removed to demon- strate the intra-articular ligament that attaches the head of the rib to the anulus. adjacent vertebrae (Fig. 5-7). The inferior and superior vex costal tubercles on the corresponding ribs. This facets on the adjacent vertebrae articulate, respectively, allows slight rotation movements between these seg- with the superior and inferior facets on the head of the ments. At the CT joints of approximately T7 through rib. The heads of the second through ninth ribs fit T10, both articular surfaces are flat and gliding motions snugly into the “angle” formed by the adjacent verte- predominate. Ribs 11 and 12 do not articulate with bral demifacets and the intervening disk and are num- their respective transverse processes of T11 or T12. bered by the inferior vertebra with which a rib articu- lates. The 1st, 10th 11th, and 12th ribs are atypical ribs The CT joint is surrounded by a thin, fibrous cap- because they articulate with only one vertebral body sule. Three major ligaments support the CT joint cap- and are numbered by that body.5,8,9 The CV facets of sule. These are the lateral costotransverse ligament, the T10 to T12 are located more posteriorly on the pedicle costotransverse ligament, and the superior costotrans- of the vertebra.6 verse ligament (Fig. 5-9). The lateral costotransverse lig- ament is a short, stout band located between the lateral The typical CV joint is divided into two cavities by portion of the costal tubercle and the tip of the corre- the interosseous or intra-articular ligament.8,9 This liga- sponding transverse process.9,10 The costotransverse ment extends from the crest of the head of the rib to ligament is composed of short fibers that run within attach to the anulus fibrosus of the intervertebral the costotransverse foramen between the neck of the disk.6,9 The radiate ligament is located within the cap- rib posteriorly and the transverse process at the same sule, with firm attachments to the anterolateral portion level.6,9 The superior costotransverse ligament runs of the capsule. The radiate ligament has three bands: from the crest of the neck of the rib to the inferior bor- the superior band, which attaches to the superior ver- der of the cranial transverse process. tebra; the intermediate band, which attaches to the intervertebral disk; and the inferior band, which atta- Costochondral and Chondrosternal Joints ches to the inferior vertebra5,6,8 (see Fig. 5-7). A fibrous The CC joints are formed by the articulation of the 1st capsule surrounds the entire articulation of each CV through 10th ribs anterolaterally with the costal carti- joint. lages (see Fig. 5-6). The CC joints are synchondroses.6 The periosteum and the perichondrium are continu- The atypical CV joints of ribs 1 and 10 through 12 are more mobile than the typical CV joints because the ▲ Figure 5-8 ■ A superior view of the costovertebral and costo- rib head articulates with only one vertebra. The transverse joints shows the capsuloligamentous structures on the interosseous ligament is absent in these joints; there- right. The joint capsules and ligaments are removed on the left to fore, they each have only one cavity.9 The radiate show the articulating surfaces. ligament is present in these joints, with the supe- rior band still attaching to the superior vertebra. Both rotation and gliding motions occur at all of the CV joints.10 Costotransverse Joints The CT joint is a synovial joint formed by the articula- tion of the costal tubercle of the rib with a costal facet on the transverse process of the corresponding verte- bra9 (Fig. 5-8). There are 10 pairs of CT joints articu- lating vertebrae T1 through T10 with the rib of the same number. The CT joints on T1 through approxi- mately T6 have slightly concave costal facets on the transverse processes of the vertebrae and slightly con-
Copyright © 2005 by F. A. Davis. CONCEPT CORNERSTONE 5-1: Rib Cage Summary 198 ■ Section 2: Axial Skeletal Joint Complexes In summary, the 1st to 10th ribs articulate posteriorly with the ver- tebral column by two synovial joints (the CV and CT joints) and Radiate anteriorly through the costocartilages to the manubriosternum, ligament either directly or indirectly. These joints form a closed kinematic chain in which the segments are interdependent and motion is Costotransverse restricted. These articulations with their associated ligamentous ligament support give the thoracic cage the stability necessary to protect Lateral the organs and yet enough flexibility to maximize function.9 The 11th and 12th ribs have a single CV joint, no CT joint, and no costotransverse attachment anteriorly to the sternum. These ribs form an open ligament kinematic chain, and the motion of these ribs is less restricted. Superior ■ Kinematics of the Ribs and Manubriosternum transverse ligament The movement of the rib cage is an amazing combina- tion of complex geometrics governed by the types and ▲ Figure 5-9 ■ Ligaments supporting the costotransverse joint, angles of the articulations, the movement of the manu- including (1) the costotransverse ligament, (2) the lateral costotrans- briosternum, and the contribution of the elasticity of verse ligament, and (3) the superior costotransverse ligament. the costal cartilages. ous, giving support to the union. The CC joints have no Controversy exists in the literature regarding the ligamentous support. mechanisms and types of motions that are actually occurring for each rib. The major controversy regard- The CS joints are formed by the articulation of the ing rib motion centers on the types of motion at the CV costal cartilages of ribs 1 to 7 anteriorly with the sternum articulations and whether the ribs can be deformed (see Fig. 5-6). Rib 1 attaches to the lateral facet of the during inspiration and expiration. Kapandji and others manubrium, rib 2 is attached via two demifacets at the believed the CV and CT joints are mechanically linked, manubriosternal junction, and ribs 3 through 7 articu- with a single axis passing through the center of both late with the lateral facets of the sternal body. The CS joints.2,8–10 Saumarez argued that the rib is rigid and, joints of the first, sixth, and seventh ribs are synchon- therefore, cannot rotate about a single fixed axis but droses. The CS joints of ribs 2 to 5 are synovial joints. rather moves as successive rotations about a shifting axis.11 The CS joints of the first through seventh ribs have capsules that are continuous with the periosteum and Investigators are generally in agreement regarding support the connection of the cartilage as a whole.9 the structure and motion of the first rib. The anterior Ligamentous support for the capsule includes anterior articulation of rib 1 is larger and thicker than that of and posterior radiate costosternal ligaments. The ster- any other rib.5 The first costal cartilage is stiffer than nocostal ligament is an intra-articular ligament, similar the other costocartilages. Also, the first CS joint is carti- to the intra-articular ligament of the CV joint, that laginous (synchondrosis), not synovial, and therefore is divides the two demifacets of the second CS joint.5,8,9 firmly attached to the manubrium. Finally, the first CS The CS joints may ossify with aging.5 The costoxiphoid joint is just inferior and posterior to the sternoclavicu- ligament connects the anterior and posterior surfaces lar joint. For these reasons, there is very little move- of the seventh costal cartilage to the front and back of ment of the first rib at the anterior CS joint. Posteriorly, the xiphoid process. the CV joint of the first rib has a single facet, which increases the mobility at that joint. During inspiration, Interchondral Joints the CV joint moves superiorly and posteriorly, elevating the first rib. The 7th through the 10th costal cartilages each articu- late with the cartilage immediately above them. For the According to what appears to be the more com- 8th through 10th ribs, this articulation forms the only monly accepted theory, there is a single axis of motion connection to the sternum, albeit indirect (see Fig. for the 1st to 10th ribs through the center of the CV 5-6). The interchondral joints are synovial joints and and CT joints. This axis for the upper ribs lies close to are supported by a capsule and interchondral liga- the frontal plane, allowing thoracic motion predomi- ments. The interchondral articulations, like the CS nantly in the sagittal plane. The axis of motion for the joints, tend to become fibrous and fuse with age. lower ribs is nearly in the sagittal plane, allowing for thoracic motion predominantly in the frontal plane (Fig. 5-10). The axis of motion for the 11th and 12th ribs passes through the CV joint only, because there is no CT joint present. The axis of motion for these last two ribs also lies close to the frontal plane. During inspiration, the ribs elevate. In the upper ribs, most of the movement occurs at the anterior
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 199 ᭣ Figure 5-10 ■ A. The common axis of motion for the upper ribs passes through the centers of the CV and CT joints and lies nearly in the frontal plane. B. The axis through the CV and CT joints for the lower ribs lies closer to the sagittal plane. aspect of the rib, given the nearly coronal axis at the 1 to rib 10) and an indirect attachment anteriorly to the vertebrae. The costocartilage become more horizon- sternum. These factors allow the lower ribs more tal.9 The movement of the ribs pushes the sternum ven- motion at the lateral aspect of the rib cage. The eleva- trally and superiorly. The excursion of the manubrium tion of the lower ribs has its greatest effect by increas- is less than that of the body of the sternum because the ing the transverse diameter of the lower thorax. This first rib is the shortest, with the caudal ribs increasing in motion that occurs in a nearly frontal plane has been length until rib 7. The discrepancy in length causes termed the “bucket-handle” motion of the thorax (Fig. movement at the MS joint.6 The motion of the upper 5-12). ribs and sternum has its greatest effect by increasing the anteroposterior (A-P) diameter of the thorax. This There is a gradual shift in the orientation of the combined rib and sternal motion that occurs in a pre- axes of motion from cephalad to caudal; therefore, the dominantly sagittal plane has been termed the “pump- intermediate ribs demonstrate qualities of both types handle” motion of the thorax (Fig. 5-11). of motion.5,8–10,12 The 11th and 12th ribs each have only one posterior articulation with a single vertebra and Elevation of the lower ribs occurs about the axis of no anterior articulation to the sternum; therefore, they motion lying nearly in the sagittal plane. The lower ribs do not participate in the closed-chain motion of the have a more angled shape (obliquity increases from rib thorax. ᭣ Figure 5-11 ■ Elevation of the upper ribs at the CV and CT joints results in anterior and superior movement of the sternum (and accompanying torsion of the costal cartilages), referred to as the “pump-handle” motion of the thorax.
Copyright © 2005 by F. A. Davis. 200 ■ Section 2: Axial Skeletal Joint Complexes A Text/image rights not available. B ▲ Figure 5-12 ■ Elevation of the lower ribs at the CV and CT joints results in a lateral motion of the rib cage, referred to as “bucket- handle” motion of the thorax. Continuing Exploration: Effects of Scoliosis ▲ Figure 5-13 ■ Although the rib cage volume changes only on the Rib Cage slightly in scoliosis, it is asymmetrically distributed, with the concave side of the thorax increasing in volume and the convex side decreas- The single axis of motion of the ribs is through the ing in volume.17 CV and CT joints. Therefore, changes in the align- ment of these joints will change the mobility of the nis, the task is also an asymmetrical one that may be thorax. In scoliosis, the thoracic vertebrae not only further compromising Mary’s ability to meet the ventila- laterally deviate but also rotate, altering the align- tory demands of her sport. ment of the costovertebral and costotransverse artic- ulating surfaces (see Fig. 5-2A and B). Although the Muscles Associated with the Rib Cage rib cage volume changes only slightly in scoliosis, it is asymmetrically distributed with the concave side of The muscles that act on the rib cage are generally the thorax (with anterior rib distortion) increasing referred to as the ventilatory muscles. The ventilatory in volume and the convex side (with posterior rib muscles are striated skeletal muscles that differ from distortion) decreasing in volume.13 Figure 5-13A is a other skeletal muscles in a number of ways: (1) the mus- view of a normal thorax in a 4-year-old. Figure 5-13B cles of ventilation have increased fatigue resistance and is a view of the thorax of a 4-year-old with a congeni- greater oxidative capacity; (2) these muscles contract tal right thoracic scoliosis, showing the rib distortion rhythmically throughout life rather than episodically; that occurs with extreme vertebral rotation. The ven- (3) the ventilatory muscles work primarily against the tilatory abilities in patients with scoliosis are affected elastic properties of the lungs and airway resistance by the angle of the deformity, the length of the rather than against gravitational forces; (4) neurologic deformity, the region of the deformity, the amount control of these muscles is both voluntary and involun- of rotation of the deformity, and the age at onset.14,15 tary; and (5) the actions of these muscles are life sus- taining. C a s e A p p l i c a t i o n 5 - 1 : Rib Distortion in Scoliosis Mary is seen by an orthopedic physician, who confirms measurement of her midthoracic scoliotic curve at 40Њ. This degree of scoliotic anglulation in the midthoracic region is likely to be accompanied by rotation of the involved vertebrae and a possible decrease in her pul- monary reserve. This may be a contributing factor in Mary’s shortness of breath during tennis play. In addi- tion to the high ventilatory demands of competitive ten-
Copyright © 2005 by F. A. Davis. Any muscle that attaches to the chest wall has the Chapter 5: The Thorax and Chest Wall ■ 201 potential to contribute to ventilation. The recruitment of muscles for ventilation is related to the type of tory reserve volume and the expiratory reserve vol- breathing being performed.16 In quiet breathing that ume. With increased ventilatory demands, the rate occurs at rest, only the primary inspiratory muscles are of breathing (breaths/minute) will also increase. needed for ventilation. During active or forced breath- ing that occurs with increased activity or with pul- Diaphragm monary pathologies, accessory muscles of both inspiration and expiration are recruited to perform the The diaphragm is the primary muscle of ventilation, increased demand for ventilation. accounting for approximately 70% to 80% of inspira- tion force during quiet breathing.17 The diaphragm is a The ventilatory muscles are most accurately classi- circular set of muscle fibers that arise from the ster- fied as either primary or accessory muscles of ventila- num, costocartilages, ribs, and vertebral bodies. The tion. A muscle’s action during the ventilatory cycle, fibers travel cephalad (superiorly) to insert into a cen- especially the action of an accessory muscle, is neither tral tendon.19,20 The lateral leaflets of the boomerang- simple nor absolute, which makes the categorizing of shaped central tendon form the tops of the domes of ventilatory muscles as either inspiratory muscles or the right and left hemidiaphragms. Functionally, the expiratory muscles inaccurate and misleading. muscular portion of the diaphragm is divided into the costal portion, which arises from the sternum, costo- ■ Primary Muscles of Ventilation cartilage and ribs, and the crural portion, which arises from the vertebral bodies21 (Fig. 5-14). The primary muscles are those recruited for quiet ven- tilation. These include the diaphragm, the intercostal The costal portion of the diaphragm attaches by muscles (particularly the parasternal muscles), and the muscular slips to the posterior aspect of the xiphoid scalene muscles.17,18 These muscles all act on the rib process and inner surfaces of the lower six ribs and cage to promote inspiration. There are no primary their costal cartilages.19,20 The costal fibers of the muscles for expiration, inasmuch as expiration at rest is diaphragm run vertically from their origin, in close passive. apposition to the rib cage, and then curve to become more horizontal before inserting into the central ten- Continuing Exploration: Measures don. The vertical fibers of the diaphragm, which lie of Lung Volume and Capacity close to the inner wall of the lower rib cage, are termed the zone of apposition2 (see Fig. 5-14A). Vital capacity (VC) is a combination of inspiratory reserve volume (IRV), tidal volume (TV), and expi- The crural portion of the diaphragm arises from ratory reserve volume (ERV). Vital capacity is the vol- the anterolateral surfaces of the bodies and disks of L1 ume of air that can be blown out of the lungs from a to L3 and from the aponeurotic arcuate ligaments. The full inspiration to a full exhalation. Inspiratory medial arcuate ligament arches over the upper anterior capacity (IC) is a combination of IRV and TV; it is part of the psoas muscles and extends from the L1 or the volume of air that can be breathed in from rest- L2 vertebral body to the transverse process of L1, L2, or ing exhalation. L3. The lateral arcuate ligament covers the quadratus lumborum muscles and extends from the transverse Functional residual capacity (FRC) is a combi- process of L1, L2, or L3 to the 12th rib19,22 (see Fig. 5- nation of expiratory reserve volume and reserve vol- 14B). ume (RV); it is the volume of air that remains in the lungs after a quiet exhalation. During tidal breathing, the fibers of the zone of apposition of the diaphragm contract, causing a Total lung capacity (TLC) is a combination of all descent of the diaphragm but only a slight change in four lung volumes: IRV, TV, ERV, and RV. Tidal vol- the contour of the dome. As the dome descends, the ume is the portion of the total lung capacity that is abdominal contents compress, increasing intra-abdom- used during quiet breathing. Table 5-1 summarizes inal pressure.22 With a deeper breath, the abdomen, the definitions graphically. With increased ventila- now compressed, acts to stabilize the central tendon of tory demands, the volume of each breath needs to the diaphragm (Fig. 5-15A), With a continued contrac- increase, moving that breath into both the inspira- tion of the costal fibers of the diaphragm against the central tendon that is stabilized by abdominal pressure, the lower ribs are now lifted and rotated outwardly in Table 5-1 Lung Volumes and Lung Capacities Lung Volumes Lung Capacities Inspiratory reserve volume Vital Capacity Inspiratory Total Lung (IRV) (VC) Capacity (IC) Capacity (TLC) Tidal volume Reserve Functional (TV) Capacity (RV) Residual Capacity Expiratory reserve volume (FRC) (ERV) Residual volume (RV)
Copyright © 2005 by F. A. Davis. 202 ■ Section 2: Axial Skeletal Joint Complexes A Central tendon Costal fibers Zone of apposition B Crural fibers Right crural Left crural fibers fibers 12th rib L3 vertebra ▲ Figure 5-14 ■ A. In an anterior view, the fibers of the diaphragm can be seen to arise from the sternum, costocartilages, and ribs (costal fibers) and from the vertebral bodies (crural fibers). The costal fibers run vertically upward from their origin in close apposition to the rib cage and then curve and become more horizontal before inserting into the central tendon. B. An inferior view of the diaphragm shows the leaflets of the central tendon, as well as the medial and lateral arcuate ligaments bilaterally. the bucket-handle motion23–25 (see Fig. 5-15B). As the nal contents to be displaced anteriorly and laterally. diaphragm reaches the end of its contraction, the fibers The resultant increase in thoracic size with descent of become more horizontally aligned, and further con- the diaphragm results in the decreased intrapulmonary traction no longer lifts the lower rib cage.26 pressure that is responsible for inspiration (Fig. 5-16). Exhalation shows a decrease in thoracic size. As the The crural portion of the diaphragm has a less diaphragm returns to its domed shape, the abdominal direct inspiratory effect on the lower rib cage than does contents return to their starting position. In persons the costal portion.2,21 Indirectly, the action of the crural with chronic obstructive pulmonary disease (COPD), portion results in a descending of the central tendon, chronic hyperinflation of the lungs results in a resting increasing intra-abdominal pressure. This increased position of the diaphragm that is lower (more flat- pressure is transmitted across the apposed diaphragm tened) than normal. Consequently, with more severe to help expand the lower rib cage.2,21 disease, an active contraction of the diaphragm pulls the lower ribs inwardly more than pulling the The thoracoabdominal movement during quiet diaphragm down (Fig. 5-17). With an active contraction inspiration is a result of the pressures that are gener- of the diaphragm in severe COPD, there is less of a ated by the contraction of the diaphragm. When the reduction in thoracic size and a decreased inspiration. diaphragm contracts and the central tendon descends, the increase in abdominal pressure causes the abdomi-
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 203 A B Descent of Pressure of the domes abdominal Pressure of viscera abdominal viscera ▲ Figure 5-15 ■ A. During tidal breathing, the diaphragm contracts, causing a descent of the dome of the diaphragm and an increase in intra-abdominal pressure. The increase in intra-abdominal pressure eventually prevents further descent of (stabilizes) the central tendon of the diaphragm. B. Continued contraction of the costal fibers of the diaphragm on the stabilized central tendon results in expansion (bucket- handle motion) of the lower ribs. Thoracic Continuing Exploration: Compliance expansion Compliance is a measurement of the distensibility of Diaphragmatic a structure or system. During diaphragm contrac- descent tion, the abdomen becomes the fulcrum for lateral expansion of the rib cage. Therefore, compliance of Anterolateral the abdomen is a factor in the inspiratory movement abdominal of the thorax. expansion Compliance ϭ ▲volume/▲pressure ▲ Figure 5-16 ■ With quiet inspiration, the normal thora- coabdominal movement is caused by contraction of the diaphragm. Compliance ϭ change in volume per unit of The diaphragm descends, increasing thoracic size and displacing the pressure abdominal viscera anteriorly and laterally. With passive exhalation, the thorax decreases in size, and the abdominal viscera return to Increased compliance of the abdomen, as in their resting position. spinal cord injury in which the abdominal muscula- ture may not be innervated, decreases lateral rib cage expansion as a result of the inability to stabilize the central tendon. Without stabilization of the cen- tral tendon, the costal fibers of the diaphragm can- not lift the lower ribs. Decreased compliance of the abdomen, as in pregnancy, limits caudal diaphrag- matic excursion and causes lateral and upward motion of the rib cage to occur earlier in the venti- latory cycle. Intercostal Muscles The external and internal intercostal muscles are cate- gorized as ventilatory muscles. However, only the parasternal muscles (or portions of the internal inter- costals adjacent to the sternum) are considered pri- mary muscles of ventilation. To provide a coordinated discussion of ventilatory musculature, the entire group
Copyright © 2005 by F. A. Davis. 204 ■ Section 2: Axial Skeletal Joint Complexes Pressure ᭣ Figure 5-17 ■ Patients with chronic obstructive pul- monary disease (COPD) have a resting position of the diaphragm that is flattened by hyperinflation. In severe dis- ease, contraction of the diaphragm pulls the lower rib cage inward. of intercostal muscles will be described together in this costal muscles originate on the inferior borders of the section. 1st through 11th ribs, and each inserts into the superior border of the rib below. The internal and external intercostal and the sub- costales muscles (Fig. 5-18) connect adjacent ribs to The functions of the intercostal muscles during one another and are named according to their ventilation are intricate and controversial. In 1749, anatomic orientation and location. The internal inter- Hamberger proposed the simplistic theory that the costal muscles arise from a ridge on the inner surfaces external intercostal muscles tend to raise the lower rib of the 1st through 11th ribs, and each inserts into the up to the higher rib, which is an inspiratory motion, superior border of the rib below. The fibers of the inter- and the internal intercostal muscles tend to lower the nal intercostal muscles lie deep to the external inter- higher rib onto the lower rib, which is an expiratory costal muscles and run caudally and posteriorly. The internal intercostals begin anteriorly at the chon- Subcostals drosternal junctions and continue posteriorly to the angles of the ribs, where they become an aponeurotic Internal layer called the posterior intercostal membrane. The intercostals external intercostal fibers run caudally and anteriorly, at an oblique angle to the internal intercostal muscles.2 Sternum External The external intercostal muscles begin posteriorly at intercostals the tubercles of the ribs and extend anteriorly to the costochondral junctions, where they form the anterior Parasternal portion of intercostal membrane. Given these attachments, only internal intercostals the internal intercostal muscles are present anteriorly from the chondrosternal junctions to the costochon- ▲ Figure 5-18 ■ Intercostal muscles. The internal intercostal dral joints. These are the segments of the internal inter- muscles originate anteriorly at the chondrosternal junction and con- costal muscles that are referred to as the parasternal tinue posteriorly to the angle of the rib, where they become an muscles. There are only external intercostal muscles aponeurotic layer. The anteriorly located fibers of the internal inter- present posteriorly from the tubercle of the ribs to the costals are referred to as the parasternal fibers. The external inter- angle of the ribs (see Fig. 5-18). Laterally, both internal costal muscles begin at the tubercle of the rib and continue anteriorly intercostal and external intercostal muscle layers are to the costochondral junction. The subcostal fibers run parallel to the present and may be referred to in this location as the internal intercostal muscles but are generally found only in the lower interosseous or lateral intercostal muscles. rib cage at the rib angle, and they may span more than one intercostal space. The subcostal muscles (see Fig. 5-18) are also inter- costal muscles but are generally found only in the lower rib cage. The subcostal muscles are found at the rib angles and may span more than one intercostal space before inserting into the inner surface of a caudal rib. Their fiber direction and action are similar to those of the internal intercostal muscles. The external inter-
Copyright © 2005 by F. A. Davis. motion.5 Electromyographic (EMG) studies have Chapter 5: The Thorax and Chest Wall ■ 205 shown that, although the external intercostal muscles are active during inspiration and the internal inter- active during the respiratory cycle, have a relatively costal muscles are active during exhalation,27 both sets small amount of activity in comparison with the of intercostal muscles may be active during both phases parasternal muscles and the diaphragm.37 The major of respiration as minute ventilation increases28 (see role of the lateral intercostal muscles is in axial rotation Continuing Exploration: Minute Ventilation). Either of the thorax, with the contralateral internal and exter- set of intercostal muscles can raise the rib cage from a nal intercostal muscles working synergistically to pro- low lung volume or lower the rib cage from a high lung duce trunk rotation (e.g., right external and left volume.29 The activation of the intercostal muscles dur- internal intercostal muscles are active during trunk ing the ventilatory cycle is from cranial to caudal, mean- rotation to the left).37 ing that the recruitment of fibers begins in the higher intercostal spaces early in inspiration and moves down- Scalene Muscles ward as inspiration progresses. Activation of the lower intercostal muscles appears to occur only during deep The scalene muscles are also primary muscles of quiet inhalation.30 ventilation.18 The scalene muscles attach on the trans- verse processes of C3 to C7 and descend to the upper Continuing Exploration: Minute Ventilation borders of the first rib (scalenus anterior and scalenus medius) and second rib (scalenus posterior) (Fig. 5- Minute ventilation is the amount of air that is 19). Their action lifts the sternum and the first two ribs breathed in (or out) in one minute: in the pump-handle motion of the upper rib cage.18,23,31 Activity of the scalene muscles begins at the onset of Minute ventilation (VE) ϭ [TV] ϫ [respiratory rate (RR)] inspiration and increases as inspiration gets closer to total lung capacity. The length-tension relationship of The parasternal muscles, the most anterior portion the scalene muscles allows them to generate a greater of the internal intercostal muscles, are considered pri- force late into the respiratory cycle, when the force mary inspiratory muscles during quiet breathing.2,31 from the diaphragm is decreasing. The scalene muscles The action of the parasternal muscles appears to be a also function as stabilizers of the rib cage. The scalene rotation of the CS junctions, resulting in elevation of muscles, along with the parasternal muscles, counteract the ribs and anterior movement of the sternum. The the paradoxical movement of the upper chest caused primary function of the parasternal muscles, however, by the decreased intrapulmonary pressure created by appears to be stabilization of the rib cage.32–34 This sta- the diaphragm’s contraction. bilizing action of the parasternal muscles opposes the decreased intrapulmonary pressure generated during ■ Accessory Muscles of Ventilation diaphragmatic contraction, preventing a paradoxical, or inward, movement of the upper chest wall during The muscles that attach the rib cage to the shoulder gir- inspiration.34 dle, head, vertebral column, or pelvis may be classified as accessory muscles of ventilation. These muscles assist The function of the lateral (internal and external) with inspiration or expiration in situations of stress, intercostal muscles involves both ventilation and trunk such as increased activity or disease. rotation.2,35,36 The lateral intercostal muscles, although When the trunk is stabilized, the accessory muscles Scalenus Scalenus medius anterior Rib 1 Scalenus posterior Rib 2 ᭣ Figure 5-19 ■ The scalenus anterior, scalenus medius, and scalenus posterior. Their action lifts the ster- num and the first two ribs in the pump-handle motion.
Copyright © 2005 by F. A. Davis. 206 ■ Section 2: Axial Skeletal Joint Complexes well as trunk flexors and rotators. The major function of the abdominal muscles with regard to ventilation is of ventilation move the vertebral column, arm, head, or to assist with forced expiration. The muscle fibers pull pelvis on the trunk. During times of increased ventila- the ribs and costocartilage caudally, into a motion of tory demand, the rib cage can become the mobile seg- exhalation. By increasing intra-abdominal pressure, the ment. The accessory muscles of inspiration, therefore, abdominal muscles can push the diaphragm upward increase the thoracic diameter by moving the rib cage into the thoracic cage, increasing both the volume and upward and outward.23 The accessory muscles of expi- speed of exhalation. ration move the diaphragm upward and the thorax downward and inward. The most commonly described Although considered accessory muscles of exhala- accessory muscles are shown in Figure 5-20A and B and tion, the abdominal muscles play two significant roles discussed in the following paragraphs. during inspiration. First, the increased intra-abdominal pressure created by the active abdominal muscles dur- The sternocleidomastoid runs from the manu- ing forced exhalation pushes the diaphragm cranially brium and superior medial aspect of the clavicle to the and exerts a passive stretch on the costal fibers of the mastoid process of the temporal bone. The usual bilat- diaphragm.2 These changes prepare the respiratory sys- eral action of the sternocleidomastoid is flexion of the tem for the next inspiration by optimizing the length- cervical vertebrae. With the help of the trapezius mus- tension relationship of the muscle fibers of the cle stabilizing the head, the bilateral action of the ster- diaphragm. Second, the increased abdominal pressure nocleidomastoid muscles moves the rib cage superiorly, created by lowering of the diaphragm in inspiration which expands the upper rib cage in the pump-handle must be countered by tension in the abdominal muscu- motion. The recruitment of this muscle seems to occur lature. Without sufficient compliance in the abdom- toward the end of a maximal inspiration.38 inal muscles, the central tendon of the diaphragm can- not be effectively stabilized so that lateral chest wall The sternocostal portion of the pectoralis major expansion occurs. During periods of increased ventila- muscle can elevate the upper rib cage when the shoul- tory needs, the increased muscular activity of the ders and the humerus are stabilized. The clavicular abdominal muscles assists in both exhalation and head of the pectoralis major can be either inspiratory inhalation.2,20 or expiratory in action, depending on the position of the upper extremity. When the arm is positioned so The transversus thoracis (triangularis sterni) mus- that the humeral attachment of the pectoralis major is cles are a flat layer of muscle that runs deep to the below the level of the clavicle, the clavicular portion parasternal muscles. The transversus thoracis muscles acts as an expiratory muscle by pulling the manubrium originate from the posterior surface of the caudal half and upper ribs down. With the humeral attachment of of the sternum and run cranially and laterally, insert- the pectoralis major above the level of the clavicle, such ing into the inner surface of the costal cartilages of as when the arm is raised, the muscle becomes an inspi- the third through seventh ribs.2 These muscles are re- ratory muscle, pulling the manubrium and upper ribs cruited for ventilation along with the abdominal mus- up and out. The pectoralis minor can help elevate the cles to pull the rib cage caudally. Studies have shown third, fourth, and fifth ribs during a forced inspiration. that these muscles are primarily expiratory muscles, The subclavius, a muscle between the clavicle and the especially when expiration is active, as in talking, first rib, can also assist in raising the upper chest for coughing, or laughing, or in exhalation into functional inspiration. residual capacity.41,42 Posteriorly, the fibers of the levatores costarum run Gravity acts as an accessory to ventilation in the from the transverse processes of vertebrae C7 through supine position. Gravity, acting on the abdominal vis- T11 to the posterior external surface of the next lower cera, performs the same function as the abdominal rib between the tubercle and the angle and can assist musculature in stabilizing the central tendon of the with elevation of the upper ribs.9,39 The serratus poste- diaphragm. In fact, in the supine position, the abdomi- rior superior (SPS) has its superior attachment at the nal muscles and the trangularis sterni are silent on the spinous processes of the lower cervical and upper tho- EMG monitoring during quiet breathing. racic vertebrae, and attaches caudally via four thin bands just lateral to the angles of the second through Continuing Exploration: Respiratory fifth ribs. The SPS and the serratus posterior inferior Changes in Scoliosis (SPI) (see Fig. 5-20B) have been assumed to be acces- sory muscles of respiration based in large part on their Not only do the anatomical changes that occur in anatomical origins and insertions. The presumed scoliosis alter the alignment and motion of the tho- actions would be elevation the ribs by the SPS, and low- rax, but also there is a consequence to the length- ering of the ribs and stabilizing the diaphragm by the tension relationship and the angle of pull of the SPI. In an article by Vilensky et al., this function was muscles of ventilation. On the side of the convexity, questioned.40 Because there is no EMG evidence to sup- with sufficient curvature, the intercostal space is port a ventilatory role of these muscles, the authors widened and the intercostal muscles are elongated. concluded that no respiratory function should be On the side of the concavity, the ribs are approxi- attributed to either muscle.40 mated and the intercostal muscles are adaptively The abdominal muscles (transversus abdominis, internal oblique abdominis, external oblique abdo- minis, and rectus abdominis) are expiratory muscles, as
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 207 A Scalenes Subclavius Sternocleidomastoid Pectoralis minor Trapezius Clavicular portion of pectoralis major Costosternal portion Transversus of pectoralis major thoracis External External obliques intercostals Rectus abdominus Internal obliques B Levatores costarum ▲ Figure 5-20 ■ Accessory muscles of ventilation are those Serratus used during times of increased ventilatory demand. A. The right side posterior of the figure shows some of the anterior superficial muscles of the inferior thorax that can be accessory muscles of ventilation, whereas the left side of the thorax shows the deeper accessory muscles of ventilation. B. The serratus posterior inferior and the levatores costarum are deep posterior muscles that may also assist with ventilation.
Copyright © 2005 by F. A. Davis. Scoliosis Inspiratory Health Capacity IRV 208 ■ Section 2: Axial Skeletal Joint Complexes shortened (see Fig. 5-2A). Lung volumes and capac- ities are reduced from those in someone without thoracic deformity, as a result of the altered biome- chanics of the scoliotic thorax43 (Fig. 5-21). C a s e A p p l i c a t i o n 5 - 2 : Treatment for Scoliosis Inspiratory IRV Total Lung CapacityTV Capacity Vital CapacityERV Bracing has been shown to be an effective treatment TV approach for limiting progression of curves and possibly Functional ERV Total Lung CapacityFunctionalRV decreasing severity of curves in some patients.44 The Residual RV Vital CapacityResidual Boston Scoliosis Brace (Fig. 5-22) is one option for Mary Capacity Capacity at this time. The Boston Scoliosis Brace places direct pressure on the rib cage in order to treat the scoliosis, IRV = Inspiratory reserve volume; TV = Tidal volume; but it also decreases thoracic mobility necessary for ERV = Expiratory reserve volume; RV = Residual volume ventilation. The brace also has a tight-fitting abdominal pad that increases intra-abdominal pressure, restricting ▲ Figure 5-21 ■ Lung volumes and capacities in health and in the descent of the diaphragm. Lung volumes and a patient with scoliosis. capacities are reduced by approximately 15% to 20% while the brace is worn.45,46 This impairment, although CONCEPT CORNERSTONE 5-2: Summary of the significant, is reversible when the brace is removed.47 Ventilatory Sequence During Breathing Bracing is likely a good option for Mary, because her curve measures 40Њ. If there is improvement in the Although the coordinated function and sequence of breathing are curve, it may improve her ability to tolerate high-level complex when activities are combined, the following sequence of activities such as tennis. motions and muscle actions is typical of a healthy person at rest during quiet breathing. The diaphragm contracts, and the central Mary is still skeletally immature, and her 40Њ curve tendon moves caudally. The parasternal and scalene muscles sta- may increase with continued growth. If bracing is not bilize the anterior upper chest wall to prevent a paradoxical inward successful in limiting progression, surgical correction movement caused by the decreasing intrapulmonary pressure. As may be considered at some point. Surgical treatment of intra-abdominal pressure increases, the abdominal contents are scoliosis generally substantially reduces or corrects the displaced in such a way that the anterior epigastric abdominal wall lateral curvature of the spine. Pulmonary function tests show that any accompanying restrictions to ventilation are improved with surgical intervention, although they are not fully normalized.48,49 Failure to normalize pul- monary mechanics may result from incomplete correc- tion of the lateral and spinal deviations, irreversible pulmonary parenchymal changes, continued rotation of the vertebrae, and decreased flexibility of the thoracic spine.48 Coordination and Integration of Ventilatory Motions The coordination and integration of the skeletal and ▲ Figure 5-22 ■ The Boston Scoliosis Brace consists of a firmly muscular chest wall components during breathing are fitting pelvic girdle that extends upward to apply forces (as appropri- complex and difficult to measure. Investigators have ate to the individual) to the ribs in a way that reverses (or limits exac- used EMG techniques, electrical stimulation, ultra- erbation of) the scoliotic curvature. sound, computed tomography (CT) scans, and com- puterized motion analysis techniques to analyze and describe chest wall motion and muscular actions.27,35–37,39 Studies have served to confirm the complexity of the coordinated actions of the many mus- cle groups involved even in quiet breathing. The recruitment of ventilatory muscles is dependent on the activities in which a person is participating, including not only sports, household, and job activities but also maintenance of posture, locomotion, speech, and defe- cation. A high and complex level of coordination is necessary for the primary and accessory muscles of ven- tilation to contribute to additional tasks while they con- tinue to perform the necessary function of ventilation.
Copyright © 2005 by F. A. Davis. Chapter 5: The Thorax and Chest Wall ■ 209 is pushed ventrally. Further outward motion of the abdominal wall A is countered by the abdominal musculature, which allows the cen- tral tendon to stabilize on the abdominal viscera. The appositional (costal) fibers of the diaphragm now pull the lower ribs cephalad and laterally, which results in the bucket-handle movement of the lower ribs. With continued inspiration, the parasternal, scalene, and levatores costarum muscles actively rotate the upper ribs and elevate the manubriosternum, which results in an anterior motion of the upper ribs and sternum. The lateral motion of the lower ribs and anterior motion of the upper ribs and sternum can occur simultaneously. Expiration during quiet breathing is passive, involv- ing the use of the recoil of the elastic components of the lungs and chest wall. Developmental Aspects of Structure and Function Differences Associated with the Neonate The compliance, configuration, and muscle action of B the chest wall changes significantly from the infant to the elderly person. The newborn has a cartilaginous, ▲ Figure 5-23 ■ A. In the adult, the ribs slope downward, and and therefore extremely compliant, chest wall that the diaphragm has an elliptical shape. B. The rib cage of an infant allows the distortion necessary for the infant’s thorax to shows a nearly horizontal alignment of the ribs, and the angle of travel through the birth canal. The increased compli- insertion of the costal fibers of the diaphragm is also more horizontal. ance of the rib cage is at the expense of thoracic stabil- ity. The infant’s chest wall muscles must act as stabilizers, rather than mobilizers, of the thorax to counteract the reduced intrapulmonary pressure cre- ated by the lowered diaphragm during inspiration. Complete ossification of the ribs does not occur for several months after birth. Whereas the ribs in the adult thorax slope down- ward and the diaphragm is elliptically shaped (Fig. 5- 23A), the rib cage of an infant shows a more horizontal alignment of the ribs, with the angle of insertion of the costal fibers of the diaphragm also more horizontal than those of the adult (see Fig. 5-23B). There is an increased tendency for these fibers to pull the lower ribs inward, thereby decreasing efficiency of ventilation and increasing distortion of the chest wall.50,51 There is very little motion of the rib cage during tidal breathing of an infant. Only 20% of the muscle fibers of the diaphragm are fatigue-resistant fibers in the healthy newborn, in comparison with 50% in the adult. This discrepancy predisposes infants to earlier diaphragmatic fatigue.51 Accessory muscles of ventilation are also at a disadvan- tage in the infant. Until infants can stabilize their upper extremities, head, and spine, it is difficult for the acces- sory muscles of ventilation to produce the action needed to be helpful during increased ventilatory demands. As the infant ages and the rib cage ossifies, muscles can begin to mobilize rather than stabilize the thorax. As the infant gains head control, he is also gaining accessory muscle use for increased ventilation. As the toddler assumes the upright position of sitting and standing, gravitation forces and postural changes allow
Copyright © 2005 by F. A. Davis. 210 ■ Section 2: Axial Skeletal Joint Complexes recruitment pattern for accessory muscles of ventila- tion. For example, the transverse thoracic muscles are for the anterior rib cage to angle obliquely downward. active during quiet expiration in older subjects in the This elliptical thorax allows for a greater bucket- standing position.41 handle motion of the rib cage. The attachments for the muscles of ventilation move with the increasingly CONCEPT CORNERSTONE 5-3: Summary angled ribs, improving their action on the thorax. of Rib Cage Changes with Aging Throughout childhood, the numbers of alveoli and air- ways continue to increase. 52 In early adolescence, the In elderly persons, there is likely to be a decreased compliance of sizes of the alveoli and airways continue to expand, as the bony rib cage, an increased compliance of the lung tissue, and demonstrated by increases in pulmonary function test an overall decreased compliance of the respiratory system as a results. result of the effects of aging. There is a decrease effectiveness of the ventilatory muscles, and ventilation becomes more energy Differences Associated with the Elderly expensive with age. There is a decreased ventilatory reserve avail- able during times of increased ventilatory need, such as increased Skeletal changes that occur with aging affect pul- activity or illness. monary function. Many of the articulations of the chest wall undergo fibrosis with advancing age.53,54 The inter- Pathological Changes in chondral and costochondral joints can fibrose, and Structure and Function the chondrosternal joints may be obliterated. The xiphosternal junction usually ossifies after age 40. The In this chapter, the effects of the musculoskeletal sys- chest wall articulations that are true synovial joints may tem on ventilation have been discussed. In scoliosis, a undergo morphologic changes associated with aging, change in the musculoskeletal structure renders a which results in reduced mobility. The costal cartilages change to ventilation. It is interesting to note that the ossify, which interferes with their axial rotation.10 opposite can also be true; changes in the pulmonary Overall, chest wall compliance is significantly reduced system can affect the biomechanics of the thorax. A with age. Reduction in diaphragm-abdomen compli- brief discussion of this relation is presented, with COPD ance has also been reported and is at least partially as the framework. related to the decreased rib cage compliance, espe- cially in the lower ribs that are part of the zone of appo- Chronic Obstructive Pulmonary Disease sition.55 The major manifestation of COPD is damage to the air- Aging also brings anatomical changes to the lung ways and destruction of the alveolar walls. As tissue tissue that affect the function of the lungs. The airways destruction occurs with disease, the elastic recoil prop- narrow, the alveolar duct diameters increase, and there erty of the lung tissue is diminished. Passive exhalation are shallower alveolar sacs. There is a reorientation and that depends upon this elastic recoil property becomes decrease of the elastic fibers. Overall, there is a de- ineffective in removing air from the thorax. Air trap- crease in the elastic recoil and an increase in pul- ping and hyperinflation occur. The static position of monary compliance.54 Because the resting position of the thorax changes as more air is now housed within the thorax depends on the balance between the elastic the lungs at the end of exhalation. This affects the lung recoil properties of the lungs pulling the ribs inwardly volume and ventilatory capacities (Fig. 5-24). and the outward pull of the bones, cartilage, and mus- cles, the reduced recoil property of the lung tissue The static resting position of the thorax is a func- allows the thorax to rest with an increased A-P diameter tion of the balance between the elastic recoil properties (a relatively increased inspiratory position). An in- of the lungs pulling inward and the normal outward creased kyphosis is often observed in older individuals, spring of the rib cage. In COPD, there is an imbalance which decreases the mobility not only of the thoracic in these two opposing forces. As elasticity decreases, an spine but also of the rib cage. increase in the A-P diameter (more of a barrel shape) of the hyperinflated thorax is apparent, along with flat- The result of these skeletal and tissue changes is an tening of the diaphragm at rest (Fig. 5-25). The range increase in the amount of air remaining in the lungs of motion, or excursion, of the thorax is limited. after a normal exhalation (i.e., an increase in func- Although the basic problem in COPD is an inability to tional residual capacity). If the lungs retain more air at exhale, it is clear that inspiratory reserve is compro- the end of exhalation, there will be a decrease in inspi- mised. ratory capacity of the thorax. Functionally, the changes result in a decrease in the ventilatory reserve available Hyperinflation affects not only the bony compo- during times of need, such as during an illness or nents of the chest wall but also the muscles of the tho- increased activity. rax. The fibers of the diaphragm are shortened, decreasing the available range of contraction. The Skeletal muscles of ventilation of the elderly person angle of pull of the flattened diaphragm fibers becomes have a documented loss of strength, fewer muscle fibers, a lower oxidative capacity, a decrease in the num- ber or the size of fast-twitch type II fibers, and a length- ening of the time to peak tension.54,56 The resting position of the diaphragm becomes less domed, with a decrease in abdominal tone in aging.10 There is an early
Copyright © 2005 by F. A. Davis. Inspiratory Health Total Lung CapacityInspiratoryCOPD1 Chapter 5: The Thorax and Chest Wall ■ 211 Capacity Vital CapacityCapacity IRV IRV TV more horizontal with a decreased zone of apposition. Functional TV Total Lung CapacityFunctional ERV In severe cases of hyperinflation, the fibers of the Residual ERV Vital CapacityResidual diaphragm will be aligned horizontally. Contraction of Capacity RV Capacity RV this very flattened diaphragm will pull the lower rib cage inward, actually working against lung inflation57 IRV = Inspiratory reserve volume; TV = Tidal volume; (see Fig. 5-17). ERV = Expiratory reserve volume; RV = Residual volume With compromise of the diaphragm in COPD, the 1COPD = Chronic obstructive pulmonary disease majority of inspiration is now performed by other inspi- ratory muscles that are not as efficient as the dia- ▲ Figure 5-24 ■ Lung volumes and capacities in health and in phragm. The barrel-shaped and elevated thorax puts a patient with COPD. the sternocleidomastoid muscles in a shortened posi- tion, making them much less efficient. The parasternal and scalene muscles are able to generate a greater force as the lungs approach total lung capacity; consequently, hyperinflation has a less dramatic effect on them.58 The diaphragm has a limited ability to laterally expand the rib cage, and so inspiratory motion must occur within the upper rib cage. In a forceful contraction of the functioning inspiratory muscles of the upper rib cage, the diaphragm and the abdominal contents actually may be pulled upward.59 This is a paradoxical thoro- coabdominal breathing pattern because the abdomen is pulled inward and upward during inspiration (Fig. 5- 26), and is pushed back out and down during exhala- Barrel-chested The upper ribs thorax move up and out Flattened The abdomen is pulled diaphragm upward and inward Protruding abdomen COPD resting position COPD inhalation ▲ Figure 5-25 ■ Resting position of a person with COPD. The ▲ Figure 5-26 ■ Paradoxical thorocoabdominal movement in thorax is barrel-shaped, and the diaphragm flattened from hyperin- COPD. With a strong pull of the accessory muscles of inspiration, flation, and the abdomen protrudes as a result of increased intra- there is an increase in the motion of the upper chest. Because the abdominal pressure. diaphragm is ineffective in descending, the abdominal viscera are pulled in and up. With exhalation, the thorax decreases in size, and the abdominal viscera return to their resting position.
Copyright © 2005 by F. A. Davis. 212 ■ Section 2: Axial Skeletal Joint Complexes Summary tion. The paradoxical pattern is a reflection of the In this chapter, comprehensive coverage of the structure and maintained effectiveness of the upper inspiratory rib function of the bony thorax and the ventilatory muscles has cage musculature and the reduced effectiveness of the been provided. Additional information on the structure and diaphragm.60 The disadvantages of these biomechani- function of accessory muscles of ventilation as these muscle cal alterations of hyperinflation are compounded by may affect the shoulder complex will be presented in the increased demand for ventilation in COPD. More Chapter 7. work is required of a less effective system. The energy cost of ventilation, or the work of breathing, in COPD is markedly increased. Study Questions 1. Describe the articulations of the chest wall and thorax, including the CV, CT, CC, CS, interchon- dral, and MS joints. 2. What is the normal sequence of chest wall motions during breathing? Explain why these motions occur. 3. What is the role of the diaphragm, the intercostal muscles, and the abdominal muscles during breathing? 4. Describe the “accessory” muscles and explain their functions. 5. Compare the action of the abdominal muscles with that of the scalene muscles. 6. What effect does COPD have on the inspiratory muscles? 7. How does the aging process affect the structure and function of the thorax? References 1. Brannon F, Foley M, Starr J, et al.: Cardiopul- 11. Saumarez RC: An analysis of possible movements of monary Rehabilitation: Basic Theory and Practice, human upper rib cage. J Appl Physiol 60:678–689, 3rd ed. Philadelphia, FA Davis, 1998. 1986. 2. De Troyer A, Estenne M: Functional anatomy of the 12. Wilson TA, Rehder K, Krayer S, et al.: Geometry respiratory muscles. Clin Chest Med 9:175–193, and respiratory displacement of human ribs. J Appl 1988. Physiol 62:1872–1877, 1987. 3. Stehbens W: Pathogenesis of idiopathic scoliosis 13. Closkey R, Schultz A, Luchies C: A model for stud- revisited. Exp Mol Pathol 74:49–60, 2003. ies of the deformable rib cage. J Biomechanics 25:529–539, 1992. 4. Leong JCY, Lu, WW, Karlberg EM: Kinematics of the chest cage and spine during breathing in 14. Brainthwaite MA: Cardiorespiratory consequences healthy individuals and in patients with adolescent of unfused idiopathic scoliosis patients. Br J Dis idiopathic scoliosis. Spine 24:1310–1323, 1999. Chest 80:360–369, 1986. 5. Williams PL: Gray’s Anatomy, 38th ed. St. Louis, 15. Campbell RM, Smith MD, Thomas C, et al.: The Elsevier, 1995. characteristics of thoracic insufficiency syndrome associated with fused ribs and congenital scoliosis. J 6. Moore KL, Dalley AF: Clinically Oriented Anatomy, Bone Joint Surg Am 85:399–408, 2003. pp 60 -173. Baltimore, Lippincott Williams & Wilkins, 1999. 16. Estenne M, Derom E, De Troyer A: Neck and abdominal muscle activity in patients with severe 7. Palastanga N, Field D, Soames R: Anatomy and thoracic scoliosis. Am J Respir Crit Care Med Human Movement: Structure and Function, 4th 158:452–457, 1998. ed. Boston, Butterworth Heinemann, 2002. 17. Tobin MI: Respiratory muscles in disease. Clin 8. Grieve GP: Common Vertebral Joint Problems, 2nd Chest Med 9:263–286, 1988. ed, pp 32–39, 110–129. New York, Churchill Livingstone, 1988. 18. De Troyer A, Estenne M: Coordination between rib cage muscles and diaphragm during quiet breath- 9. Winkel D: Diagnosis and Treatment of the Spine, ing in humans. J Appl Physiol 57:899–906, 1984. pp 393–401. Gaithersburg, MD, Aspen, 1996. 19. Panicek DM, Benson CB, Gottlieb RH, et al.: The 10. Kapandji IA: The Physiology of the Joints: The diaphragm: Anatomic, pathologic and radiographic Trunk and Vertebral Column, 3rd ed. New York, considerations. Radiographics 8:385–425, 1988. Churchill Livingstone, 1990.
Copyright © 2005 by F. A. Davis. 20. Celli BR: Clinical and physiologic evaluation of res- Chapter 5: The Thorax and Chest Wall ■ 213 piratory muscle function. Clin Chest Med 10:199– 214, 1989. 40. Vilensky J, Baltes M, Weikel L, et al.: Serratus pos- terior muscles: Anatomy, clinical relevance and 21. De Troyer A, Sampson M, Sigrist S, et al.: The dia- function. Clin Anat 14:237–241, 2001. phragm: Two muscles. Science 213:237–238, 1981. 41. De Troyer A, Ninane V, Gilmartin JJ, et al.: Trian- 22. Deviri, E, Nathan, H, Luchansky, E: Medial and lat- gularis sterni muscle use in supine humans. J Appl eral arcuate ligaments of the diaphragm: Physiol 62:919–925, 1987. Attachment to the transverse process. Anat Anz 166:63–67, 1988. 42. Estenne M, Ninane V, De Troyer A: Triangularis sterni muscle use during eupnea in humans: Effect 23. Celli BR: Respiratory muscle function. Clin Chest of posture. Respir Physiol 74:151–162, 1988. Med 7:567–584, 1986. 43. Upadhyay S, Mullaji A, Luk K, et al.: Relation of 24. Epstein S: An overview of respiratory muscle func- spinal and thoracic cage deformities and their flex- tion. Clin Chest Med 15:619–638, 1994. ibilities with altered pulmonary functions in adoles- cent idiopathic scoliosis. Spine 20:2415–2420, 1995. 25. De Troyer A, Sampson M, Sigrist S, et al.: Action of costal and crural parts of the diaphragm on the rib 44. Rowe DE, Bernstein SM, Riddick MF, et al.: A meta- cage in dog. J Appl Physiol 53:30–39, 1982. analysis of the efficacy of non-operative treatment for idiopathic scoliosis. J Bone Joint Surg Am 26. Reid WD, Dechman G: Considerations when test- 79:664–674, 1997. ing and training the respiratory muscles. Phys Ther 75:971–982, 1995. 45. Lisboa C, Moreno R, Fava M, et al.: Inspiratory mus- cle function in patients with severe kyphoscoliosis. 27. De Troyer A, Kelly S, Zin WA: Mechanical action of Am Rev Respir Dis 46:53–62, 1985. the intercostal muscles on the ribs. Science 220:87–88, 1983. 46. Refsum HE, Naess-Andersen CF, Lange EJ: Pulmonary function and gas exchange at rest and 28. LeBars P, Duron B: Are the external and internal exercise in adolescent girls with mild idiopathic intercostal muscles synergistic or antagonistic in scoliosis during treatment with Boston thoracic the cat? Neurosci Lett 51:383–386, 1984. brace. Spine 15:420-3, 1990. 29. Van Luneren E: Respiratory muscle coordination. J 47. Korovessis P, Filos K, Feorgopoulos D: Long term Lab Clin Med 112:285–300, 1988. alterations of respiratory function in adolescents wearing a brace for idiopathic scoliosis. Spine 30. Koepke GH, Smith EM, Murphy AJ, et al.: Se- 21:1979–1984, 1996. quence of action of the diaphragm and intercostal muscles during respiration. I. Inspiration. Arch 48. Gagnon S, Jodoin A, Martin R: Pulmonary function Phys Med Rehabil 39:426–430, 1958. test study and after spinal fusion in young idio- pathic scoliosis. Spine 14:486–490. 1989. 31. De Troyer A: Actions of the respiratory muscles or how the chest wall moves in upright man. Bull Eur 49. Upadhyay SS, Ho EKW, Gunawardene WMS, et al.: Physiopathol Respir 20:409–413, 1984. Changes in residual volume relative to vital capac- ity and total lung capacity after arthrodesis of the 32. De Troyer A, Heilporn A: Respiratory mechanics in spine in patients who have adolescent idiopathic quadriplegia. The respiratory function of the inter- scoliosis. J Bone Joint Surg Am 75:46–52, 1993. costal muscles. Am Rev Respir Dis 122:591–600, 1980. 50. Crane, LD: Physical therapy for the neonate with respiratory dysfunction. In Irwin S, Tecklin JS 33. Macklem PT, Macklem DM, De Troyer A: A model (eds): Cardiopulmonary Physical Therapy, 3rd ed, of inspiratory muscle mechanics. J Appl Physiol pp 486–515. St. Louis, CV Mosby, 1995. 55:547–557, 1983. 51. Davis GM, Bureau MA: Pulmonary and chest wall 34. Cala SJ, Kenyon CM, Lee A, et al.: Respiratory ultra- mechanics in the control of respiration in the new- sonography of human parasternal intercostal mus- born. Clin Perinatol 14:551–579, 1987. cles in vivo. Ultrasound Med Biol 24:313–326, 1998. 52. Reid L: Lung growth. In Zorab PA (ed): Scoliosis 35. De Troyer A, Kelly S, Macklem PT, et al.: Mechanics and Growth: Proceedings of a Third Symposium, of intercostal space and actions of external and pp 117–121. Edinburgh, Churchill Livingstone, internal intercostal muscles. J Clin Invest 75:850– 1971. 857, 1985. 53. Krumpe PE, Knudson RJ, Parsons G, et al.: The 36. Rimmer KP, Ford GT, Whitelaw WA: Interaction aging respiratory system. Clin Geriatr Med between postural and respiratory control of human 1:143–175, 1985. intercostal muscles. J Appl Physiol 79:1556–1561, 1995. 54. Chan ED, Welsh CH: Geriatric respiratory medi- cine. Chest 114:1704–1733, 1998. 37. Whitelaw WA, Ford GT, Rimmer KP, et al.: Inter- costal muscles are used during rotation of the tho- 55. Estenne M, Yernault JC, De Troyer A: Rib cage and rax in humans. J Appl Physiol 72:1940–1944, 1992. diaphragm-abdomen compliance in humans: Effects of age and posture. J Appl Physiol 38. Raper AJ, Thompson WT, Shapiro W, et al.: Scalene 59:1842–1848, 1985. and sternomastoid muscle function. J Appl Physiol 21:497–502, 1966. 56. Makrides L, Heigenhauser GJ, McCartney N, et al.: Maximal short-term exercise capacity in healthy 39. Goldman MD, Loh L, Sears TA: The respiratory subjects aged 15–70 years. Clin Sci (Lond) activity of human levator costal muscle and its mod- 69:197–205, 1985. ification by posture. J Physiol 362:189–204, 1985.
Copyright © 2005 by F. A. Davis. 214 ■ Section 2: Axial Skeletal Joint Complexes 60. De Troyer A: Respiratory muscle function in chronic obstructive pulmonary disease. In Cassa- 57. De Troyer A: Effect of hyperinflation on the dia- bury R, Petty T (eds): Principles and Practice of phragm. Eur Respir J 10:703–713, 1997. Pulmonary Rehabilitation. Philadelphia, WB Saun- ders, 1995. 58. Decramer M: Hyperinflation and respiratory mus- cle interaction. Eur Respir J 10:934–941, 1997. 59. Camus P, Desmeules M: Chest wall movements and breathing pattern at different lung volumes [abstract]. Chest 82:243, 1982.
Copyright © 2005 by F. A. Davis. 6 Chapter The Temporomandibular Joint Don Hoover, PT, PhD, Pamela Ritzline, PT, EdD Introduction Muscular Control of the Temporomandibular Joint Relationship with the Cervical Spine Structure Dentition Articular Surfaces Articular Disk Age-Related Changes in the Capsule and Ligaments Temporomandibular Joint Upper and Lower Temporomandibular Joints Dysfunctions Function Inflammatory Conditions Mandibular Motions Capsular Fibrosis Mandibular Elevation and Depression Osseous Mobility Conditions Mandibular Protrusion and Retrusion Articular Disk Displacement Mandibular Lateral Deviation Degenerative Conditions 6-1 Patient Case Screening of body systems beyond the musculoskeletal system is negative. Wendy Doe is a 31-year-old housewife with three children younger than 6 years. Her visit to the clinic is prompted by fre- Introduction quent headaches and intermittent aching pain in the right jaw area. Wendy is right-handed, and her history is unremarkable The TM joint is unique within the body both struc- except for a reported history of allergies and a period of physical turally and functionally. Structurally, the mandible is a abuse that occurred over a period of months when she was 23 horseshoe-shaped bone (Fig. 6-1) that articulates with years old. She reports that the headaches started intermittently the temporal bone at each end; thus, the mandible has after she was first struck in the face by her boyfriend. Over the two different but connected articulations. Each TM years, the headaches have gotten progressively more intense and joint also has a disk that separates the articulation into frequent. The symptoms in the area of her right jaw are reportedly discrete upper and lower joints that each function triggered when she tries to eat an apple or a large sandwich. She slightly differently. Therefore, mandibular movement also reports an occasional “popping” noise that accompanies affects four distinct joints simultaneously. In all, the TM opening her mouth but states that the noise is not associated joint is a complex joint that moves in all planes of with pain. motion. Wendy’s physical examination reveals a forward head pos- Each TM joint is formed by the condyle (or head) ture, rounded shoulders, and increased thoracic kyphosis. Her of the mandible inferiorly and the articular eminence right shoulder is slightly elevated. She demonstrates limitations in of the temporal bone superiorly (Fig. 6-2), with an active movement when performing mouth opening, mandibular interposed articular disk (Fig. 6-3). The lower joint protrusion, and left lateral excursion of the mandible. Restricted formed by the mandibular condyle and the inferior sur- movement of the mandibular condyle on the right side during face of the disk is a simple hinge joint. The upper joint mouth opening is noted. Active range of motion of the cervical formed by the articular eminence and the superior sur- spine is limited, especially the upper segmental levels. Passive face of the disk is a plane or gliding joint. Classic work range of motion of the cervical spine is also limited. Palpation of by Sicher1 described the TM joint as a hinge joint with the right temporomandibular (TM) joint is painful. Wendy also movable sockets, and later authors supported this reports tenderness with palpation of the muscles at the back of description.2,3 The TM joint is classified as a synovial her head, the sides of her face, and under her chin bilaterally. joint, although no hyaline cartilage covers the articular Wendy’s strength and reflexes appear to be within normal limits. 215
Copyright © 2005 by F. A. Davis. 216 ■ Section 2: Axial Skeleton Joint Complexes Head Mandibular notch Coronoid process Ramus Base of Angle mandible Body ᭣ Figure 6-1 ■ The mandible. surfaces. The surfaces are instead covered by dense col- Structure lagenous tissue described as fibrocartilage, with a great capacity to remodel in response to physical load.4 Both Articular Surfaces the articular eminence of the temporal bone and the condyle of the mandible are convex structures, result- The proximal or stationary segment of the TM joint is ing in an incongruent joint. The disk increases stability the temporal bone. The condyles of the mandible sit while minimizing loss of mobility. The articular disk is in the glenoid fossa of the temporal bone (see Fig. 6-3). necessary to reduce friction and avoid biomechanical The glenoid fossa is located between the posterior gle- stress on the joint.4–6 Functionally, few other joints are noid spine and the articular eminence of the temporal moved as often as the TM joint. Mandibular motion bone. The glenoid fossa, on superficial inspection, plays a role in phonation, facial expression, mastica- looks like the articular surface for the TM joint. tion, and swallowing. The muscles surrounding the TM However, the bone in that area is thin and translucent joint create great forces during biting or chewing, and and not at all appropriate for an articular surface.1–3,7–9 yet they generate finely controlled motion that requires The articular eminence, however, has a major area of little force during speaking and swallowing. These activ- trabecular bone and serves as the primary articular sur- ities have obvious importance in the lives of all individ- face for the mandibular condyle.10,11 uals. The TM joint exhibits a combination of complexity, almost continuous use, and capacity for force and finesse that is remarkable. Upper joint Articular eminence (glenoid fossa) Disk Posterior gelnoid spine of temporal Mandibular bone Condyle Lower joint Coronoid ▲ Figure 6-3 ■ A cross-sectional lateral view of the TM joint process shows the fibrocartilage-covered load-bearing surfaces on the condyle of the mandible and the articular eminence. The TM disk divides the ▲ Figure 6-2 ■ Lateral view of the articulation of the mandible articulation into an upper joint and a lower joint, each with its own with the articular eminence of the temporal bone. synovial lining. The anterior and posterior attachments of the joint capsule (squiggly lines) to the disk are shown.
Copyright © 2005 by F. A. Davis. The mandible is the distal or moving segment of Chapter 6: The Temporomandibular Joint ■ 217 the TM joint. The mandible is divided into a body and two rami, with each ramus having a coronoid process ▲ Figure 6-5 ■ Palpation of the posterior mandibular condyle and a mandibular condyle (see Fig. 6-1). In the closed- through the external auditory meatus. mouth position, the coronoid process sits under the zygomatic arch, but it can be palpated below the arch but also to tremendous bite forces that have been meas- when the mouth is open. The coronoid process serves ured at 597 N for women and 847 N for men.14 The TM as an attachment for the muscle. joint surfaces are amenable to some degree of adapta- tion, but there is no clear-cut point between adaptive The mandibular condyles are located at the end of and maladaptive changes.15 Unlike the fibrocartilage the ramus at its most posterosuperior aspect, with each on the mandibular condyles and articular eminences, having a medial and a lateral pole (Fig. 6-4). Each the articular disk of the TM joint does not have the abil- condyle protrudes medially 15 to 20 mm from the ity to repair and remodel.16 ramus.1,2,7,12 The portion of the condyle that can be readily palpated is the lateral pole. This bony landmark Articular Disk lies just in front of the external auditory meatus of the ear. The medial pole is deep and cannot be palpated. The articular disk of the TM joint is biconcave; that is, However, the posterior aspect of the condyle can be pal- both its superior and inferior surfaces are concave (Fig. pated if a fingertip is placed into the external auditory 6-6). Styles and Whyte described the disk as having a meatus and the pad of the finger is pushed anteriorly “bowtie” appearance on magnetic resonance imaging (Fig. 6-5).8 As the jaw is opened and closed, the move- (MRI) film, with the “knot” lying at the thinnest por- ment under the fingertip is that of the mandibular tion.17 The articular disk varies in thickness, from 2 mm condyle. Lines following the axis of mediolateral poles anteriorly to 3 mm posteriorly and to 1 mm in the mid- of each condyle will intersect just anterior to the fora- dle.12 The disk of the TM joint allows the convex sur- men magnum (see Fig. 6-4).1,3,4 The anterior portion of face of the articular eminence and the convex surface the mandibular condyle is the articular portion and is of the condyle to remain congruent throughout the composed of trabecular bone.10,11 range of TM motion.9,12 The anterior and posterior portions of the disk are vascular and innervated; the The articular surfaces of the articular eminence of middle segment, however, is avascular and not inner- the temporal bone and the mandibular condyle are vated.9,12,18 The lack of vascularity and innervation is covered with dense, avascular collagenous tissue that consistent with the fact that the middle portion of the contains some cartilaginous cells.13 Because some of disk is the force-accepting segment. the cells are cartilaginous, the covering is often re- ferred to as fibrocartilage.7,9 The articular collagen The disk has a complex set of attachments. The fibers are aligned perpendicular to the bony surface in disk appears to be firmly attached to the medial and the deeper layers to withstand stresses. The fibers near lateral poles of the condyle of the mandible but not to the surface of the articular covering are aligned in a the TM joint capsule medially or laterally.3 These parallel arrangement to facilitate gliding of the joint attachments allow the condyle to rotate freely on the surfaces.7,9 The presence of fibrocartilage rather than disk in an anteroposterior direction. Although the hyaline cartilage is significant because fibrocartilage medial and lateral attachments of the disk cannot be can repair and remodel.7,9 Typically, fibrocartilage is present in areas that are intended to withstand repeated and high-level stress. The TM joints are sub- jected not only to the repetitive stress of jaw motions Lateral Pole Foramen Magnum Lateral Pole Medial Pole ▲ Figure 6-4 ■ A superior view of the mandible (removed from the skull) shows the medial and lateral poles of the mandibular condyles. Mandibular rotation occurs around axes that pass through the medial and lateral poles of the right and left condyles, with the lines intersecting anterior to the foramen magnum of the skull.
Copyright © 2005 by F. A. Davis. 218 ■ Section 2: Axial Skeleton Joint Complexes Superior lamina A healthy TM disk is viscoelastic and well suited to the distribution of force, showing only minor changes in Tympanic Superior portion connective tissue fiber waviness even under significant membrane lateral pterygoid stress.18 The disk consists primarily of collagen, glycosa- muscle minoglycans (GAGs), and elastin. Collagen is largely responsible for the disk’s maintaining its shape. Elastin Joint capsule contributes to the disk’s regaining its form during unloading. GAG composition maintains disk resiliency Areolar and resists mechanical compressive force. The biome- tissue Inferior chanical behavior of the disk may change according to changes in its composition.18 Such changes in composi- lamina tion may occur as a result of aging, mechanical stress, or both.14 ▲ Figure 6-6 ■ The TM disk attaches posteriorly to the joint capsule and to the superior and inferior laminae (segments of the bi- Capsule and Ligaments laminar retrodiskal pad). The disk attaches anteriorly to the joint cap- sule and to the lateral pterygoid muscle. The TM joint capsule is not as well defined as many joint capsules. According to Gray’s Anatomy, the joint is readily shown, Figure 6-6 shows the anterior and poste- supported by short capsular fibers running from the rior attachments of the disk. The disk is attached to the temporal bone to the disk and from the disk to the joint capsule anteriorly, as well as to the tendon of the neck of the condyle.13 The portion of the capsule above lateral pterygoid muscle. The anterior attachments the disk is quite loose, whereas the portion of the cap- restrict posterior translation of the disk. Posteriorly, the sule below the disk is tight.3,13 Consequently, the disk is disk is attached to a complex structure, the compo- more firmly attached to the condyle below and freer to nents of which are collectively called the bilaminar move on the articular eminence above. The capsule is retrodiskal pad. The two bands (or laminae) of the bil- quite thin and loose in its anterior, medial, and poste- aminar retrodiskal pad are each attached to the disk. rior aspects, but the lateral aspect (Fig. 6-8) is stronger The superior lamina is attached posteriorly to the tym- and is reinforced with long fibers (temporal bone to panic plate (at the posterior glenoid fossa).12,19 The condyle).3,13 The lack of strength of the capsule anteri- superior lamina is made of elastic fibers that allow the orly and the incongruence of the bony articular sur- superior band to stretch. The superior lamina allows faces predisposes the joint to anterior dislocation of the the disk to translate anteriorly along the articular emi- mandibular condyle.1 The capsule is highly vascular- nence during mouth opening (Fig. 6-7); its elastic ized and innervated, which allows it to provide a great properties assist in repositioning the disk posteriorly deal of information about position and movement. during mouth closing. The inferior lamina is attached to the neck of the condyle and is inelastic. The inferior The primary ligaments of the TM joint are the tem- lamina simply serves as a tether on the disk, limiting poromandibular (TM) ligament, the stylomandibular forward translation, but does not assist with reposition- ligament, and the sphenomandibular ligament (see Fig. ing the disk during mouth closing.12,16,17 Neither of the 6-8). The TM ligament is a strong ligament that is com- laminae of the retrodiskal pad is under tension when posed of two parts. The outer oblique portion (shown the TM joint is at rest. Between the two laminae is loose in Fig. 6-8) attaches to the neck of the condyle and the areolar connective tissue rich in arterial and neural articular eminence. It serves as a suspensory ligament supply.6,12,16 and limits downward and posterior motion of the mandible, as well as limiting rotation of the condyle Superior lamina on stretch during mouth opening.3,9,12 The inner portion of the ligament is attached to the lateral pole of the condyle ▲ Figure 6-7 ■ With full mouth opening, the disk and the and posterior portion of the disk and to the articular condyle together translate anteriorly. The inferior lamina limits trans- eminence. Its fibers are almost horizontal and resist lation, and the elastic properties of the superior lamina both control posterior motion of the condyle. Limitation of poste- anterior translation and assist with posterior translation during mouth rior translation of the condyle protects the retrodiskal closing. pad.12 Neither of the bands of the TM ligament limits forward translation of the condyle or disk, but they do limit lateral displacement.19 The stylomandibular ligament is a band of deep cervical fascia that runs from the styloid process of the temporal bone to the posterior border of the ramus of the mandible. Some authors have identified its func- tion as limitation to protrusion of the jaw,2,9,12 whereas others have stated that it has no known function.1,20,21 The sphenomandibular ligament attaches to the spine of the sphenoid bone and to the middle surface
Copyright © 2005 by F. A. Davis. TM joint Oblique portion of Chapter 6: The Temporomandibular Joint ■ 219 capsule temporomandibular a wide range of positions, allowing greater flexibility of ligament the disk as the condyle first rotates beneath it and then translates with it over the articular eminence.3,12,16,17 Sphenomandibular The thick-thin-thick arrangement of the disk also pro- ligament vides a self-centering mechanism for the disk on the condyle.3,12,16,17 As pressure between the condyle and (inner mandible) the articular eminence increases, the disk rotates on the condyle so that the thinnest portion of the disk is Stylomandibular between the articulating surfaces. Like other con- ligament nective tissues in the body, the function of the disk may be disrupted by physical stress over time or pro- found trauma.14 As we examine the motions of the jaw (mandible), the role of and potential for problems with the disk will become more evident. Function ▲ Figure 6-8 ■ A lateral view of the TM joint capsule and liga- The TM joint is one of the most frequently used joints ments. in the body. It is involved in talking, chewing, and swal- lowing. Most TM joint movements are empty-mouth of the ramus of the mandible. Abe and colleagues22 movements16 (e.g., talking); that is, they occur with no stated that the sphenomandibular ligament also has resistance from food or contact between the upper and continuity with the disk medially. Some authors have lower teeth. The joint is well designed for this intensive stated that it serves to suspend the mandible5 and to use. The cartilage covering the articular surfaces is de- check the mandible from excessive forward transla- signed to tolerate repeated and high-level stress. In tion.2,9,16 Other authors, however, have stated that this addition to a joint structure that supports the high level ligament also has no function.13,20,21 of usage, the musculature is designed to provide both power and intricate control.16 Speech requires fine con- Upper and Lower trol of the jaw, and the ability to chew requires great Temporomandibular Joints strength. The TM disk divides the TM joint into two separate Mandibular Motions joint spaces, each with its own synovial lining. Synovial fluid supplies the nutritional demands of the fibrocarti- The motions of the TM joint are mouth opening lage covering the joint surfaces and the avascular mid- (mandibular depression), mouth closing (mandibular dle portion of the disk. Intermittent pressure on these elevation), jutting the chin forward (mandibular pro- collagenous structures during joint motion causes the trusion), sliding the teeth backward (mandibular retru- synovial fluid to be pumped in and out of them, pro- sion), and sliding the teeth to either side (lateral viding their nutrition. deviation of the mandible). These motions are created by various combinations of rotation and gliding in the The lower joint of the TM articulation functions upper and lower joints. The motions involved in chew- effectively as a hinge joint. The firm attachments of the ing, talking, and swallowing become quite complex. For disk to the medial and lateral poles of the condyle allow purposes of this chapter, we will describe only the move- free rotation of the condyle under the disk around an ments of the mandible that occur without resistance axis through both poles of the condyle, with little trans- (empty-mouth movements). latory motion occurring. The upper joint of the TM articulation functions as a plane joint, with the loose ■ Mandibular Elevation and Depression attachment of the disk to the temporal bone allowing translatory movement between the disk and articular In normally functioning TM joints, mandibular eleva- eminence. The attachments between the disk and tion and depression are relatively symmetrical motions. condylar poles that permit rotation between these The motion at each TM joint follows a similar pattern. structures in the lower joint cause the condyle and disk Two distinct and somewhat conflicting descriptions of to translate forward (glide) together as a unit with the movement of mouth opening can be found in the upper joint motion. literature. One conceptual framework describes two sequential phases: rotation and glide.2,4,21 In the rota- The biconcave shape of the disk provides unique tion phase of mouth opening, there is pure anterior advantages to the TM articulation’s dual joint surfaces. rotation (spin) of the condyle on the disk in the lower The disk’s shape provides increased congruence through joint (Fig. 6-9A). This has also been described as poste- rior rotation of the disk on the condyle. The second
Copyright © 2005 by F. A. Davis. Superior portion of 220 ■ Section 2: Axial Skeleton Joint Complexes lateral pterygoid muscle A Inferior portion of lateral pterygoid muscle ▲ Figure 6-10 ■ Another conceptual framework holds that B condylar rotation on the disk and anterior translation of the disk and condyle on the articular eminence occur concomitantly during mouth opening. ▲ Figure 6-9 ■ A. During initial mouth opening, the motion at front incisors, the amount of opening is functional, the TM joint may be limited to anterior rotation of the condyle on the although a fit of three PIP joints is considered normal disk. B. Anterior translation of the condyle and disk together on the (Fig. 6-11).4 Dijkstra and associates demonstrated a pos- articular eminence may occur in the latter stages of mouth opening. itive correlation between the amount of mouth open- ing and the length of the mandible. This should be phase involves translation of the disk-condyle unit ante- considered in determining what is normal for each riorly and inferiorly along the articular eminence (see patient.26 Figs. 6-9B and 6-7). This motion occurs in the upper joint between the disk and the articular eminence and Mandibular elevation (mouth closing) is the accounts for the remainder of the opening. Normal reverse of depression. It consists of translation of the mouth opening is considered to be 40 to 50 mm.5,8 Of disk-condyle unit posteriorly and superiorly and of pos- that motion, between 11 mm13,23 and 25 mm12 is gained terior rotation of the condyle on the disk. from rotation of the condyle in the disk, whereas the Control of the Disk during Mandibular remainder is from translation of the disk and condyle Elevation and Depression along the articular eminence. The articular disk is controlled both actively and pas- sively during mouth opening and closing. The passive The second model, based on more recent research, control is exerted by the capsuloligamentous attach- argues that the components of rotation and gliding are ments of the disk to the condyle. Active control of the present but occur concomitantly rather than sequen- disk may be exerted through the disk’s attachment tially (Fig. 6-10).23–25 That is, both rotation and gliding are present throughout the range of mandibular de- ▲ Figure 6-11 ■ Mandibular depression (mouth opening) is pression and elevation, starting at the initiation of considered within normal limits if the proximal interphalangeal mouth opening. Isberg and Westesson also noted that joints of two fingers can be inserted between the teeth. the amount of rotation has a positive correlation with the steepness of the articular eminence.23 For a quick and rough, but useful, estimate of function, the clinician may use the proximal interpha- langeal (PIP) joints to assess opening. If two PIP joints can be placed between the upper and lower central
Copyright © 2005 by F. A. Davis. Chapter 6: The Temporomandibular Joint ■ 221 anteriorly to the superior portion of the lateral ptery- ▲ Figure 6-12 ■ With maximum mandibular protrusion, the goid muscle (see Fig. 6-6 and Fig. 6-10), although evi- lower teeth should be in front of the upper teeth. dence suggests that these attachments may not be consistently present.22,27 Bell also proposed two other condyle translates forward.12,13 For example, deviation muscles that may assist with maintaining the disk posi- to the right would involve the right condyle spin- tion.16 These two muscles are derived from the masseter ning and the left condyle translating or gliding forward muscle and are attached to the anterolateral portion of (Fig. 6-13). The result is movement of the chin to the the disk. They help overcome the medial pull of the right. Normally, the amount of lateral excursion of the anteromedially directed lateral pterygoid. joint is about 8 mm.8 A functional measurement of lateral motion of the mandible involves the use of the During mouth opening, the medial and lateral at- tachments of the disk to the condyle limit the motion Rotation around between the disk and condyle to rotation. During trans- a vertical axis lation of the condyle, the biconcave shape of the disk causes it to follow the condyle without any additional Translation active or passive assistance. The inferior retrodiskal lam- ina limits forward excursion of the disk. The superior Lateral deviation portion of the lateral pterygoid muscle appears to be to the right positioned to assist with anterior translation of the disk but does not show activity during mouth opening.8,16 ▲ Figure 6-13 ■ In this superior view of the mandible, lateral deviation of the mandible (chin) to the right occurs effectively as a During mouth closing, the elastic character of the rotation (spin) of the right condyle around a vertical axis, and the left superior retrodiskal lamina applies a posterior distrac- condyle translates anteriorly. tive force on the disk. In addition, the superior portion of the lateral pterygoid now demonstrates activity that is assumed to eccentrically control the posterior movement of the disk. The activity of the superior lateral pterygoid allows the disk-condyle complex to translate upward and posteriorly during mouth closing and then main- tains the disk in a forward position until the condyle has completed its posterior rotation on the disk or until the disk has rotated anteriorly on the condyle.28–30 Abe and colleagues suggested that the spheno- mandibular ligament also assists this action. Again, the medial and lateral attachments of the disk to the con- dyle limit the motion to rotation of the disk around the condyle.22 ■ Mandibular Protrusion and Retrusion This motion occurs when all points of the mandible move forward the same amount. The condyle and disk together translate anteriorly and inferiorly along the articular eminence. No rotation occurs in the TM joint during protrusion. The motion is all translation and occurs in the upper joint alone. The teeth are separated when protrusion occurs (Fig. 6-12). During protrusion, the posterior attachments of the disk (the bilaminar retrodiskal tissue) stretch 6 to 9 mm to allow the motion to occur.12 Protrusion should be adequate to allow the upper and lower teeth to touch edge to edge.8 Retrusion occurs when all points of the mandible move posteriorly the same amount. Tension in the tem- poromandibular ligament limits this motion, as does compression of the soft tissue in the retrodiskal area between the condyle and the posterior glenoid spine. Although rarely measured, retrusion is limited to an estimated 3 mm of translation.12 ■ Mandibular Lateral Deviation In lateral deviation of the mandible (chin) to one side, one condyle spins around a vertical axis and the other
Copyright © 2005 by F. A. Davis. 222 ■ Section 2: Axial Skeleton Joint Complexes Muscular Control of the Temporomandibular Joint ▲ Figure 6-14 ■ With normal lateral deviation of the mandible The primary muscle responsible for mandibular de- to the right, the midline of the lower teeth should move the full width pression is the digastric muscle (Fig. 6-15).16 The pos- of the right upper central incisor. terior portion of the digastric muscle arises from the mastoid notch, whereas the anterior portion arises width of the two upper central incisors. If the man- from the inferior mandible. The tendon that joins the dible can move the full width of one of the central anterior and posterior portions is connected by a fib- incisors in each direction, motion is considered normal rous loop to the hyoid bone in the neck. The hyoid (Fig. 6-14).8 bone must be stabilized for the digastric muscle to act as a depressor of the mandible. The lateral pterygoid Lateral deviation of the mandible can be consid- muscles are considered to be mandibular depres- ered a normal asymmetrical movement of the jaw. sors,3,10,13,29 but Bell considered this limited to the infe- Another normal asymmetrical movement involves rota- rior portion alone (with the superior portion silent tion of one condyle around an anteroposterior axis during mouth opening).16 Gravity is also a mandibular while the other condyle depresses.12 This results in a depressor. The contribution of the mandibular eleva- frontal plane motion of the mandible in which the chin tors to eccentric control of mandibular depression is moves downward and deviates from the midline slightly unclear.3 toward the condyle that is spinning. This motion typi- cally occurs during biting on one side of the jaw. Al- Mandibular elevation is accomplished primarily by though these motions were just described separately, several muscles. The temporalis muscle attaches to the they are commonly combined into one complex inside of the coronoid process (Fig. 6-16). The mas- motion used in chewing and grinding food. seter muscle is attached to the outer surface of the angle and ramus of the mandible (Fig. 6-17). The medial pterygoid muscle is attached to the inner surface of the angle and ramus of the mandible (Fig. 6-18).13,28 As we have already seen, the superior portion of the lat- eral pterygoid is also active during mouth closing in what is assumed to be eccentric control of the disk as the disk-condyle complex translates upward and pos- teriorly and then in maintaining the disk in a forward C a s e A p p l i c a t i o n 6 - 1 : Palpation and Asymmetry Posterior portion of of Motion digastric muscle Wendy Doe demonstrates decreased active range of Anterior portion of motion with mouth opening, with mandibular protrusion Hyoid bone digastric muscle and left lateral deviation. When palpating fingers are placed in her ears, the mandibular condyles moved with ▲ Figure 6-15 ■ The posterior portion of the digastric muscle marked asymmetry during mouth opening. The left arises from the mastoid notch, and the anterior portion arises from condyle appears to move considerably more than the the inferior mandible. The tendon that joins the anterior and poste- right. This may indicate that the condyles are not rotat- rior portions is connected by a fibrous loop to the hyoid bone in the ing or that the condyles and disk are not translating neck. either with the same magnitude or in the same se- quence on the right and the left. This may indicate either hypomobility on the right, or hypermobility on the left.
Copyright © 2005 by F. A. Davis. Chapter 6: The Temporomandibular Joint ■ 223 Temporalis muscle Coronoid process of mandible ▲ Figure 6-16 ■ The temporalis muscle, with its attachment to ▲ Figure 6-18 ■ The medial and lateral pterygoid muscles. the medial aspect of the coronoid process. position until the condyle has completed its posterior mandible but in different sequences. Mandibular pro- rotation as the condyle returns to its normal rest trusion is produced by bilateral action of the masseter, position. medial pterygoid,4,21 and lateral pterygoid muscles.12,31 Retrusion is produced through the bilateral action of CONCEPT CORNERSTONE 6-1: Summary: Mandibular the posterior fibers of the temporalis muscles with assis- Elevation and Depression tance from the anterior portion of the digastric mus- cle.13 Lateral deviation of the mandible is caused by Mouth opening (mandibular depression) is initiated by concentric unilateral action of a selected set of these muscles. The action of the digastric muscles bilaterally, and by the inferior por- medial and lateral pterygoid muscles each deviate the tion of the lateral pterygoid muscles. Mouth closing (mandibular mandible to the opposite side.12,13 The temporalis mus- elevation) is produced by the collective concentric action of the cle can deviate the mandible to the same side. masseter, temporalis, and medial pterygoid muscles, with eccentric Although the temporalis and lateral pterygoid muscles control of the TM disks by the superior lateral pterygoid muscles. on the left, for example, appear to create opposite motions of the mandible, concomitant contractions of The other simple mandibular motions of protru- the right lateral pterygoid and right temporalis muscles sion, retrusion, and lateral deviation are produced by function as a force couple. The lateral pterygoid muscle the same muscles that elevate and depress the is attached to the medial pole of the condyle and pulls the condyle forward. The temporalis muscle on the same side is attached to the coronoid process and pulls it posteriorly. Together they effectively spin the condyle to create deviation of the mandible to the left. Because the temporalis muscle is also an elevator of the mandible, this combination of muscular activity is par- ticularly useful in chewing. ▲ Figure 6-17 ■ The masseter muscle. Relationship with the Cervical Spine The cervical spine and the TM joint are intimately con- nected. Many of the muscles that attach to the mandible also have attachments to the head (cranium), to the hyoid bone, and to the clavicle. Consequently, muscles may act not only on the mandible but also on the atlanto-occipital joint and cervical spine. Head and neck position, too, may affect the tension in cervical muscles that, in turn, may affect the position or func- tion of the mandible. Proper posture minimizes the force produced by the cervical extensors and other cervical muscles necessary to support the weight of
Copyright © 2005 by F. A. Davis. cally lessen the capacity of particular structures to meet the thresholds for adaptive responses to physi- 224 ■ Section 2: Axial Skeleton Joint Complexes cal stresses. Increased tension from shortening of the suboccipital tissues may lead to headaches that the head. Poor cervical posture over time may lead to originate in the suboccipital area, limitation in active adaptive shortening or lengthening in muscles around range of motion of the upper cervical spine, and TM the head and cervical spine, affecting range of motion, joint dysfunction. Furthermore, pain in the TM muscular force production capacity, and joint mor- region may be referred from the cervical region.34,37 phology in the involved region. Many of the symptoms Thus, it is proposed that cervical posture should be reported by a person with TM joint dysfunction are sim- normalized to successfully treat dysfunction in the ilar to the symptoms reported by a person with primary TM joint complex32,34,37 (Fig. 6-19B). cervical spine problems. With the intimate relationship of these two areas, any client being seen for complaints Continuing Exploration: TM/Respiratory/ in one area should have the other examined as Cervical Dysfunction well.11,32–34 TM joint disorders may develop as a result of dys- Continuing Exploration: TM/Cervical functional growth and developmental patterns that Joint Interrelationships may accompany conditions such as chronic sinus allergies.38 To illustrate, a child with allergies who A forward head posture frequently involves exten- has difficulty breathing through the nose will often sion of the occiput and the upper cervical spine, hyperextend the upper cervical spine to more fully leading to compensatory flattening of the lower cer- open the upper respiratory tract. Such a cervical pos- vical spine and upper thoracic spine to achieve a ture places the upper and lower teeth in contact with level head position35 (Fig. 6-19A). With the occiput each other and may affect the resting position of the extended on the atlas (C1), the suboccipital tissues TM joint. In turn, the muscles surrounding the TM adapt and shorten. The suboccipital tissues include joint complex expend greater energy to maintain the anterior atlantoaxial and atlanto-occipital liga- this posture and have more difficulty resting and ments (cephalad continuations of the ligamentum repair. Resistance to inspiration may also lead to use flavum), the posterior belly of the digastric muscles, of accessory muscles of respiration (scalene and ster- the stylohyoid muscles, and the upper fibers of the nocleidomastoid muscles) to assist with breathing. upper trapezius, semispinalis capitis, and splenius Use of these accessory muscles may lead to a forward capitis muscles.36 The forces necessary to maintain the head against gravity with a poor cervical posture and forward head result in muscle imbalance and altered movement patterns. Such alterations typi- Text/image rights not available. AB ▲ Figure 6-19 ■ A. Poor cervical posture increases the physical demands on the suboccipital structures, contributing to TM joint dysfunction. B. Corrected cervical posture restores the muscles of the cervical spine and TM joint to a more balanced length- tension relationship.
Copyright © 2005 by F. A. Davis. head posture.38 Such a posture contributes over time Chapter 6: The Temporomandibular Joint ■ 225 to a cycle of increasing musculoskeletal dysfunction, including repeated episodes of TM inflammation in the musculoskeletal system are considered, we must that can result in fibrosis of the TM joint capsule. understand that normal aging is not necessarily syn- onymous with degenerative changes, nor are all degen- C a s e A p p l i c a t i o n 6 - 2 : Posture and TM erative changes synonymous with disability. Rowe and Joint Relations Kahn40 described successful aging as “multidimen- sional, encompassing the avoidance of disease and dis- Wendy Doe’s complaints of frequent headaches and ability, the maintenance of high physical and cognitive intermittent aching pain in the right jaw area may be function, and sustained engagement in social and pro- associated with her posture. Wendy’s physical examina- ductive activities.” We know that tissues are likely to tion reveals a forward head, rounded shoulders, and an become less supple, less elastic, and less able to with- increased thoracic kyphosis (see Fig. 6-19A). The stand maximal forces with aging, leading to biome- observed elevation of Wendy’s right shoulder may indi- chanical changes in musculoskeletal tissues as one cate tightness of the suboccipital tissues, consistent progresses through the life span. However, these with her demonstrated limitation in active movement changes will not necessarily become pathologic or lead when performing mandibular depression (mouth open- to biomechanical dysfunction. Conversely, degenera- ing), mandibular protrusion, and left lateral excursion of tive changes may be a result of preexisting dysfunction the mandible. Wendy also reports tenderness with pal- and not a result of aging alone. pation of the muscles at the back of her head, the sides of her face, and under her chin bilaterally. Tenderness In a study at autopsy of 37 TM joints of persons age and muscle guarding may be related to the stresses 55 to 99 years, Nannmark et al. reported structural placed on the tissues from improper positioning.35 changes in 38% of the examined mandibular con- dyles.41 The authors found no signs of inflammatory Dentition cell infiltration in any TM joint specimens, which sug- gested that observed changes were secondary to biome- Occlusion, or contact of the teeth, is intimately involved chanical stresses rather than to inflammatory processes. in the function of the TM joint. Although the teeth are Twenty-two (59%) of the TM disks had perforations, only together approximately 15 minutes of each day, roughness, or were thinned. However, only 3 (8%) of the presence and position of the teeth are critical to the disks were in an anterior position, and each of these normal TM joint function. Chewing is one of the func- was perforated. The authors concluded that osteo- tions of the TM joint, and contact of the upper and arthritis may be expected in 14% to 40% of adults, with lower teeth limits motion of the TM joint during empty- increased frequency with age in both men and mouth movements. The complexities of the TM joint women.41 and the interrelated issues with the teeth underscore the necessity of the comprehensive management of TM De Leeuw and colleagues conducted radiography joint disorders. and MRI of 46 former patients 30 years after diagnosis of osteoarthrosis and internal derangement of the TM Normal adult dentition includes 32 teeth divided joint.42 Internal derangement of the TM joint is an into four quadrants. The only teeth we will refer to by abnormal positional and functional relationship name are the upper and lower central incisors. These between the disk and articulating surfaces.3 De Leeuw are the two central teeth of the maxilla and the two cen- and colleagues’ patients were between the ages of 50 tral teeth of the mandible.39 When the central incisors and 70 years at the time of the follow-up study. The are in firm approximation, the position is called maxi- investigators also performed similar imaging on 22 age- mal intercuspation7 or the occlusal position.13 This is matched controls without known TM joint dysfunc- not, however, the normal resting position of the tion.42 Radiographic signs were more common and mandible. Rather, 1.5 to 5.0 mm of “freeway” space severe in the former patients. A higher percentage of between the upper and lower incisors is normally main- osteoarthrosis and internal derangement of the disk tained.12,16 This freeway space is particularly important. was noted on MRI not only on the side of TM joint By maintaining this space, the intra-articular pressure problems but also in the contralateral joints. However, within the TM joint is decreased, the stress on the artic- the contralateral joints appeared to have developed ular structures is reduced, and the tissues of the area these degenerative changes largely asymptomatically are able to rest and repair.12 (with only 25% reporting any symptoms and none hav- ing sought treatment). Control subjects only infre- Age-Related Changes in the quently showed MRI evidence of osteoarthrosis or Temporomandibular Joint internal derangement. The TM joint is affected by the aging process. However, The work done by Nannmark et al. and by de Leeuw as is the case when age-related changes in other joints and colleagues appears to indicate that TM degenera- tion is not an expected part of aging and that degener- ative changes evident on radiograph or MRI are not necessarily associated with symptoms or dysfunction. Tanaka and coworkers found that disks from patients with severe internal derangement demon- strated more extensive degenerative changes than those from controls.18 The authors described patterns of collagen fiber running more irregularly in deranged
Copyright © 2005 by F. A. Davis. 226 ■ Section 2: Axial Skeleton Joint Complexes however, clinicians should be aware that rheumatoid arthritis often involves the temporomandibular joint.44 disks than in the disks of the control group. The authors related the structural changes in the disks with Capsular Fibrosis internal derangement to the diminished capacity of these tissues to withstand mechanical stress. Tanaka and Inflammation can lead to adhesions that restrict the coworkers found a cause-effect relationship, with inter- movement of the disk and limit the function of the TM nal derangement leading to disk damage.18 joint.17 Capsular fibrosis in the TM joint complex may arise from unresolved or chronic inflammation of the Dysfunctions joint capsule, which results in the overproduction of fibrous connective tissue.4,44 The resultant fibrosis Although many dysfunctions may impact the TM joint, causes progressive damage and loss of tissue func- mechanical stress is the most critical factor in the mul- tion.4,44 A client history suggesting repeated episodes of tifactorial etiology.10,18,43 Some dysfunctions are caused capsulitis is key in identifying this condition. by direct trauma such as motor vehicle accidents or Circumstances leading to chronic capsulitis and, in falls. Others are the result of years of poor postural or turn, capsular fibrosis may include prolonged periods oral habits such as forward head posture or bruxism of immobilization, trauma, or arthritis.4 Active motion (grinding of the teeth). Most clients with temporo- of the TM joint capsule will typically elicit pain. Physical mandibular dysfunction (TMD) will not fit neatly into a examination will reveal limited or altered osteokine- specific category or dysfunction classification, which matic motions, suggestive of a decrease in translatory makes evaluation and treatment of TMD a particularly motion in the involved side.4 challenging clinical endeavor. Furthermore, only 20% to 30% of individuals affected with internal derange- C a s e A p p l i c a t i o n 6 - 3 : Trauma and TM Dysfunction ment of the TM joint develop symptomatic TM joints,3 with symptoms that may progress or may resolve spon- Ms. Doe’s musculoskeletal complaints may be attributa- taneously.17 Because of the complex interrelationships ble to capsular fibrosis, as well as to her poor posture. It associated with various types of TMD, practitioners is likely that she had an acute episode of capsulitis in interested in diagnosis and treatment of this clinical response to first to being hit in the face by her population should seek advanced education in this boyfriend. A common mechanism would be that the area. Here, we will present a small group of problems trauma to the face caused a stretching force on the ipsi- that were chosen to represent the most common forms lateral TM joint and a compression force on the con- of TM joint complex dysfunction: inflammatory condi- tralateral TM joint, resulting in an inflammatory process tions, capsular fibrosis, osseous mobility conditions, art- with edema and pain in both TM areas. Repeated icular disk displacement, and degenerative conditions. assaults may have exacerbated the inflammation without the opportunity for resolution, leading to a chronic and Inflammatory Conditions progressive capsular fibrosis.4 Inflammatory conditions of the TM joint include cap- Osseous Mobility Conditions sulitis and synovitis. Capsulitis involves inflammation of the joint capsule, and synovitis is characterized by a Osseous mobility disorders of the TM joint complex fluctuating swelling caused by effusion within the sy- include joint hypermobility and dislocation. Many sim- novial membrane of the joint. Rheumatoid arthritis is ilarities exist in the history and clinical findings for the most common cause of such inflammatory condi- these two conditions. Excessive motion, or hypermobil- tions, but gout, psoriatic arthritis, ankylosing spondylitis, ity, of the TM joint is a common phenomenon found in systemic lupus erythematosus, juvenile chronic arthri- both symptomatic and nonsymptomatic populations.4 tis, and calcium pyrophosphate dehydrate deposition Joint hypermobility may be a generalized connective may also contribute to inflammation of the synovia.3 tissue disorder that involves all joints of the body, Individuals with inflammatory conditions may experi- including the TM joints.28,38,45–47 The hypermobility is a ence diminished mandibular depression as a result of result of laxity of the joint capsules, tendons, and liga- pain and inflammation within the joint complex.4 ments. Individuals seen clinically for this condition typ- ically report the jaw “going out of place,” producing Rheumatoid arthritis is a chronic systemic condi- noises, or “catching” when the mouth is in the fully tion with articular and extra-articular involvement. The opened position. Physical examination of patients with primary symptoms of rheumatoid arthritis include TM joint hypermobility reveals an increased indenta- pain, stiffness, edema, and warmth. This autoimmune tion posterior to the lateral pole. Joint noises occur at disorder targets the capsule, ligamentous structures, the end of mandibular depression and at the beginning and synovial lining of the joint complex, resulting in of mandibular closing. These noises may be heard by joint instability, joint deformity, or ankylosis.44 Multiple the patients but are more often palpable only by the bilateral joints are typically involved with this disease. clinician. Hypermobility of one TM joint results in Clients with rheumatoid arthritis should be managed medically by a rheumatologist, particularly during the acute stage of the disease. Detailed discussion of rheumatoid arthritis is beyond the scope of this text;
Copyright © 2005 by F. A. Davis. deflection of the mandible toward the contralateral Chapter 6: The Temporomandibular Joint ■ 227 side with mouth opening. In addition, mandibular depression will exceed 40 mm.4 Yang et al. examined tively limited. The later the click occurs in the opening the MRIs of 98 patients diagnosed with TM joint hyper- phase, the more severe the disk dislocation is.4 Some mobility, or overmovement of the condyle during jaw evidence exists that the timing of the clicks during opening.28 They found pathological changes (hypertro- opening and closing can determine treatment prog- phy, atrophy, or contracture) in 77% of the lateral nosis.48 pterygoid muscles, with changes more common in the superior portion of the muscle. The authors often Individuals with disk displacement with reduction found anterior disk displacement with reduction in the may remain in this state or progress rapidly, within patients who reported more symptoms than in persons months, to an acute condition of disk displacement with normal mobility or with disk displacement without without reduction. The posterior attachments to the reduction.28 disk become overstretched and unable to relocate the disk during mandibular depression, which results in Many aspects of the history and physical examina- the loss of the reciprocal clicks.17 Yang et al. discovered tion of an individual with dislocation of the TM joint on MRI a highly significant correlation between abnor- are similar to those in an individual with hypermobility. malities of the lateral pterygoid muscles and TM joints However, with TM joint dislocation, full mouth opening with disk displacements both with and without reduc- results in deflection (lateral deviation) of the jaw to the tion of the disk.28 The abnormalities of the lateral contralateral side of the involved TM joint, and the pterygoid muscle noted included hypertrophy, contrac- inability to close the mouth. The individual may or may ture, and atrophy of the superior and inferior bellies not experience pain with this condition. With disloca- of the lateral pterygoid muscles of the involved TM tion, both the mandibular condyle and the disk have joint. Recall that the lateral pterygoid muscle attaches translated anteriorly well beyond the articular crest of to the anterior portion of the disk and is normally the tubercle of the temporal bone, thus “sticking” in active with mouth closing, presumed to be eccentrically the extreme end-range position.4,17 This condition is controlling the return to resting position. Hypertrophy usually temporary and resolves with joint mobilization; of this muscle indicates overactivity, which thus possibly however, intervention is beyond the scope of this text leads to the excessive anterior translation of the articu- and therefore will not be discussed. lar disk.28 Articular Disk Displacement Whether acute or chronic, disk displacement with- out reduction indicates that the disk does not relocate The articular disk of the TM joint may sublux, con- onto the mandibular condyle. Thus, clients with acute tributing to dysfunction in this joint.17,29 Articular disk disk displacement without reduction demonstrate lim- displacement conditions include disk displacement ited mandibular motion as a result of the disk’s creating with reduction and disk displacement without reduc- a mechanical obstruction to condylar motion, rather tion.4,28,29 Without intervention, disk displacement with than facilitating condylar translation. Individuals with reduction often evolves to disk displacement without disk displacement without reduction typically describe reduction.4,17,28,29 Disk displacement (internal derange- an inability to fully depress the mandible, as well as dif- ment) may be identified through diagnostic imaging or ficulty performing functional movements involving the through physical examination.17 MRI is the imaging jaw such as chewing, talking, or yawning. modality of choice for identifying disk displacement.3 Degenerative Conditions Individuals exhibiting disk displacement with reduction experience “joint noise” at two intervals: dur- Primarily two conditions affect the TM joint: osteo- ing mandibular opening and mandibular closing. This arthritis and rheumatoid arthritis. Rheumatoid arthritis joint noise is known as a reciprocal click4,17 and is a key is discussed previously under inflammatory conditions. sign in diagnosing disk displacement with reduction. In Kessler and Hertling5 stated that 80% to 90% of the this situation, the mandibular condyle is in contact with population older than 60 years have some symptoms of the retrodiskal tissue at rest, rather than with the disk. osteoarthritis in the TM joint. Yang et al. concurred On mouth opening, the condyle slips forward and with MRI evidence to substantiate their findings.28 under the disk to obtain a normal relationship with the According to Mahan,19 osteoarthritis usually occurs uni- disk. When the condyle slips under the disk, an audible laterally (unlike rheumatoid arthritis, which is usually click is often present. Once the condyle is in the proper bilateral in presentation). The primary cause of relationship with the disk, motion continues normally osteoarthritis is repeated minor trauma to the joint, through opening and closing until the condyle again particularly trauma that creates an impact between the slips out from under the disk, when another click is articular surfaces.17,19 Styles and Whyte17 suggested that heard. A click would be expected to signify that the the radiographic features of degenerative changes in condyle and disk have lost a normal relationship. In the the TM joint, including joint space narrowing, erosions, case of an anteriorly dislocated disk, however, the initial osteophyte formation, sclerosis, and remodeling, are click signifies regaining a normal relationship. When similar to those seen elsewhere in the body. Loss of pos- the click occurs early in opening and late in closing, terior teeth may also contribute to degenerative the amount of anterior displacement of the disk is rela- changes because simple occlusion of the remaining teeth alters the forces that occur between the TM joint forces.4,19
Copyright © 2005 by F. A. Davis. 228 ■ Section 2: Axial Skeleton Joint Complexes CONCEPT CORNERSTONE 6-2: Signs and Symptoms of variables, it does suggest that these biomechanical vari- TM Joint Dysfunction ables may play a role in a patient’s pain presentation. In turn, clinical interventions aimed at improving structural Clinical signs and symptoms of TM joint dysfunction vary widely, balance of the head, neck, and thorax are important depending on the extent of the condition and the presence of augmentations to any direct intervention at the TM joint. complicating factors. Signs and symptoms may include Task modification in her work environment and stress management may also be therapeutic adjuncts. ■ pain in the area of the jaw ■ increased or decreased active or passive range of motion Summary ■ popping or clicking noises ■ difficulty with functional activities (e.g., eating, talking) or The TM joints are unique both structurally and functionally. The magnitude and frequency of jaw movement, the daily parafunctional activities (e.g., clenching, nail biting, pencil resistance encountered during chewing, the physical stress chewing) of the mandible imposed by sustained sitting and standing postures, and the ■ catching or locking of the jaw chronic adaptation of muscles around the TM joint complex ■ forward head posture make it particularly vulnerable to problems. The influence of the cervical spine upon the TM joint must always be recog- C a s e A p p l i c a t i o n 6 - 4 : Patient Summary nized. Intervention for clients with temporomandibular disor- ders presents many clinical challenges, and practitioners Wendy Doe sought physical therapy because of frequent with interest in this population should seek advanced educa- headaches and intermittent aching in the right jaw area. tion beyond the entry level in this specialty area. As we pro- Her symptoms may be attributable to a number of ceed in subsequent chapters to examine the joint complexes potential sources in isolation—trauma to the TM joint, of the appendicular skeleton, it will be seen that each com- poor cervical posture, forward head position—or in some plex has its own unique features. We will not see again, combination of these sources. Factors such as stress of however, the complexity of intra-articular and diskal motions work and family life or bruxism may also play a role in seen at the TM joints. her clinical presentation. Although the research litera- ture does not explicitly draw a direct link between these Study Questions 1. Describe the articulating surface of the TM joint. 2. What is the significance of the differing thicknesses and the differing vascularity of the disk? 3. How do the superior and inferior laminae of the retrodiskal area differ? 4. Describe the motions in the upper and lower joints during mouth opening and closing. 5. What limits posterior motion of the condyle? How is the motion limited? 6. What would be the consequences of having a left TM joint that could not translate? 7. What would be the consequences of having a right disk that could not rotate freely over the condyle? 8. Describe the control of the disk in moving from an open-mouth to a closed-mouth position. 9. What is the potential impact of the posture of the cervical spine on the function of the TM joint complex? 10. Compare and contrast the functional presentation of a hypomobile versus hypermobile TM joint complex. References 1. Sicher H: Functional anatomy of the temporoman- 3. Sommer O, Aigner F, Rudisch A, et al.: Cross- dibular joint. In Sarnat B (ed): The Temporomandi- sectional and functional imaging of the temporo- bular Joint, 2nd ed. Springfield, IL, Charles C mandibular joint: Radiology, pathology, and basic Thomas, 1964. biomechanics of the jaw. In Radiographics 23:e14, 2003. 2. Hylander W: Functional anatomy. In Sarnat BG, Laskin DM (eds): The Temporomandibular Joint: A 4. Kraus S: Temporomandibular joint. In Saunders Biological Basis for Clinical Practice. Philadelphia, H, Saunders R (eds): Evaluation, Treatment, and WB Saunders, 1992. Prevention of Musculoskeletal Disorders, 3rd
Copyright © 2005 by F. A. Davis. ed. Bloomington, MN, Educational Opportunities, Chapter 6: The Temporomandibular Joint ■ 229 1993. 5. Kessler R, Hertling D: Management of Common 21. Helland M: Anatomy and function of the temporo- mandibular joint. J Orthop Sports Phys Ther Musculoskeletal Disorders: Physical Therapy 1:145–152, 1980. Principles and Methods, 3rd ed. Philadelphia, Lippincott-Raven, 1996. 22. Abe S, Ouchi Y, Ide Y, et al.: Perspectives on the role 6. Magee D: Orthopedic Physical Assessment, 4th ed. of the lateral pterygoid muscle and the spheno- Philadelphia, WB Saunders, 2002. mandibular ligament in temporomandibular joint 7. Ermshar C: Anatomy and neuroanatomy. In Mor- functions. Cranio 15:203–207, 1997. gan D, House L, Wall W, et al. (eds): Diseases of the Temporomandibular Apparatus: A Multidiscipli- 23. Isberg A, Westesson P: Steepness of articular emi- nary Approach, 2nd ed. St. Louis, CV Mosby, 1982. nence and movement of the condyle and disk in 8. Kraus S: Temporomandibular joint. In Saunders H, asymptomatic temporomandibular joints. Oral Saunders R (eds): Evaluation, Treatment, and Surg Oral Med Oral Pathol Oral Radiol Endod Prevention of Musculoskeletal Disorders, 2nd ed. 86:152–157, 1998. New York, Viking Press, 1985. 9. Eggleton TL, Langton DM: Clinical anatomy of the 24. Lindauer SJ, Sabol G, Isaacson RJ, et al.: Condylar TMJ complex. In Krauss SL (ed): Temporoman- movement and mandibular rotation during jaw dibular Disorders, 2nd ed. New York, Churchill opening. Am J Orthod Dentofacial Orthop Livingstone, 1994. 107:573–577, 1995. 10. Matsumoto M, Matsumoto W, Bolognese A: Study of the signs and symptoms of temporomandibular 25. Ferrario VF, Sforza C, Miani A Jr, et al.: Open-close dysfunction in individuals with normal occlusion movements in the human temporomandibular and malocclusion. Cranio 20:274–281, 2002. joint: Does a pure rotation around the intercondy- 11. Moya H, Miralles R, Zuniga C, et al.: Influence of lar hinge axis exist? J Oral Rehabil 23:401–408, stabilization occlusal splint on craniocervical rela- 1996. tionships. Part I: Cephametric analysis. Cranio 12: 47–51, 1994. 26. Dijkstra PU, Hof AL, Stegenga B, et al.: Influence 12. Bourbon B: Anatomy and biomechanics of the of mandibular length on mouth opening. J Oral TMJ. In Kraus S (ed): TMJ Disorders: Management Rehabil 26:117–122, 1999. of the Craniomandibular Complex. New York, Churchill Livingstone, 1988. 27. Naidoo L: Lateral pterygoid muscle and its rela- 13. Williams P: Gray’s Anatomy, 38th ed. New York, tionship to the meniscus of the temporomandibu- Churchill Livingstone, 1999. lar joint. Oral Sur Oral Med Oral Pathol Oral 14. Waltimo A, Kononen M: A novel bite force recor- Radiol Endod 82:4–9, 1996. der and maximal isometric bite force values for healthy young adults. Scand J Dent Res 101: 28. Yang X, Pernu H, Pyhtinen J, et al.: MRI findings 171–175, 1993. concerning the lateral pterygoid muscle in patients 15. Mueller M, Maluf K: Tissue adaptation to physical with symptomatic TMJ hypermobility. Cranio stress: A proposed “physical stress theory” to guide 19:260–268, 2001. physical therapist practice, education, and research. Phys Ther 2:383–403, 2002. 29. Yang X, Pernu H, Pyhtinen J, et al.: MR abnormali- 16. Bell W: Temporomandibular Disorders: Classifi- ties of the lateral pterygoid muscle in patients with cation, Diagnosis, Management, 3rd ed. Chicago, nonreducing disk displacement of the TMJ. Cranio Year Book Medical, 1990. 20:209–221, 2002. 17. Styles C, Whyte A: MRI in the assessment of inter- nal derangement and pain within the temporo- 30. Bade H, Schenck C, Koebke J: The function of dis- mandibular joint: A pictorial essay. Br J Oral comuscular relationships in the human temporo- Maxillofac Surg 40:220–228, 2002. mandibular joint. Acta Anat (Basel) 151:258–267, 18. Tanaka E, Shibaguchi T, Tanaka M, et al.: Visco- 1994. elastic properties of the human temporomandibu- lar joint disc in patients with internal derangement. 31. Murray GM, Orfanos T, Chan JY, et al.: Electromyo- J Oral Maxillofac Surg 58:997–1002, 2000. graphic activity of the human lateral pterygoid 19. Mahan P: The temporomandibular joint in func- muscle during contralateral and protrusive jaw tion and pathofunction. In Solberg W, Clark GT movements. Arch Oral Biol 44:269–285, 1999. (eds): Temporomandibular Joint Problems: Biologic Diagnosis and Treatment. Chicago, 32. Hellsing E: Changes in the pharyngeal airway in Quintessence, 1980. relation to extension of the head. Eur J Orthod 20. Loughner B, Gremillion HA, Mahan PE, et al.: 11:359–365, 1989. The medial capsule of the human temporoman- dibular joint. J Oral Maxillofac Surg 55:363–369, 33. Evcik D, Aksoy O: Correlation of temporomandibu- 1997. lar joint pathologies, neck pain and postural differ- ences. J Phys Ther Sci 12:97–100, 2000. 34. Ciancaglini R, Testa M, Radaelli G: Association of neck pain with symptoms of temporomandibular dysfunction in the general adult population. Scand J Rehab Med 31:17–22, 1999. 35. Saunders H, Saunders R: Evaluation, Treatment and Prevention of Musculoskeletal Disorders, 3rd ed. Chaska, MN, The Saunders Group, 1993. 36. Netter F: Atlas of Human Anatomy, 3rd ed. Teterboro, NJ, Icon Learning Systems, 2003. 37. Ali H: Diagnostic criteria for temporomandibular joint disorders: A physiotherapist’s perspective. Physiotherapy 88:421–426, 2002.
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