Normal Standing Alignment

In standing, the normal alignment of the thoracic spine is a flexion curve of 40 degrees, as measured using a Cobb angle.^3,13-23 Clinically, a normal thoracic spine has a mild posterior convexity and even distribution of flexion (Figure 4-3). The shape of the thoracic curve is attributed to a slight wedging of the vertebrae.⁹⁶ A lateral view of a chest x-ray shows that the anterior aspects of the vertebral bodies are slightly smaller than the posterior aspect²⁴ (Figure 4-4). There are no known sex differences in the overall amount of normal thoracic flexion alignment^17,25,26; however, with aging, there is an increase in thoracic flexion, with females demonstrating a greater increase than males.¹⁷,²⁵

Figure 4-3 A and B, Normal thoracic alignment.

(B, From Kendall FP, McCreary EK, Provance PG: Muscles: testing and function, ed 4, Philadelphia, 1993, Lippincott Williams & Wilkins.)

Figure 4-4 Normal thoracic curve.

The normal rib cage is slightly rounded in circumference—the superior aspect of the rib cage is more narrow than the inferior aspect. The rib cage is normally symmetrical from side to side. The shape of the rib cage can be attributed to the variation in the length and curvature of the ribs and their anterior attachment to the sternum. The angle formed by the costal margins of ribs 7 to 10 is referred to as the subcostal margin. An ideal subcostal angle of approximately 90 degrees is considered to be a reflection of balance between the length of the internal and external oblique muscles.^1-27 Age-related changes of the rib cage have not been well studied; clinical observations indicate that individuals with a thoracic kyphosis, as well as individuals with central obesity, will have a flaring of the lower ribs. Reported sex differences of the rib cage indicate that males tend to have a narrower anterior-to-posterior dimension and a broader medial-to-lateral dimension, whereas females tend to have a more rounded chest wall with a narrower overall diameter²⁸ (Figure 4-5).

Figure 4-5 Male: Greater medial to lateral width (black line) than anterior posterior width (gray line). Female: Medial to lateral width (red line) is similar to anterior posterior width (pink line).

Impaired Standing Alignment

Alignment impairments of the thoracic spine can be both postural and structural. Postural impairments are flexible and respond to positional changes or cues to change alignment. Structural alignment impairments are fixed alignments of the boney structures that persist, regardless of the position of the individual. Though structural changes are present, some correction may be possible if connective tissues are extensible. Genetic variation in tissue mobility is a factor in determining the magnitude of alignment change. A structural impairment can be demonstrated with radiographic studies. Attempts to change a structural alignment may increase stress across a region and may worsen a pain syndrome by forcing motion above or below the malaligned segments. For example, cueing an individual with a structural kyphosis to extend the thoracic spine often results in an increase in lumbar or cervical extension. Recognition of a structural impairment and accommodation for the fixed impairment must be made to reduce mechanical stresses and pain. Patients may also present with a combination of structural and postural alignment impairments. In this case, attempts at postural correction may be only partially successful.

There are five categories of impaired thoracic alignment: kyphosis, posterior trunk sway, flat back, rotation, and scoliosis. Thoracic kyphosis is defined as an increase in the flexion curve in the thoracic region³,²⁹ (Figure 4-6). With a sustained postural kyphosis, structural accommodation to the persistent anterior forces on the vertebral bodies results in increasing disc and vertebral body loading, causing a wedging of the thoracic vertebrae.⁵ In this case, kyphosis that started as a postural fault becomes a structural impairment according to the principles of Wolff’s law. This phenomenon commonly is not painful until a severe kyphosis has developed.

Figure 4-6 Kyphosis.

Individuals with a thoracic kyphosis commonly have a lumbar lordosis.²⁹ Specific movement testing may help to determine if the kyphosis-lordosis alignment is (1) structural (fixed), (2) caused by weakness or excessive length of thoracic extensor muscles, or (3) caused by passive stiffness or frequent (habitual) contraction of the abdominal musculature, specifically the RA. Usually, when the kyphosis is structural, the thoracic curvature does not change when the patient is examined in the supine, prone, and quadruped position even when instructed to straighten the thoracic spine. Although a structural kyphosis can occur at any age, older individuals with degenerative changes and osteoarthritis are more likely to have a structural kyphosis.

Scheuermann’s disease, or juvenile kyphosis, is a structural impairment believed to occur as the result of a variation in the growth of the endplates of the vertebral bodies.³⁰ However, the etiology of Scheuermann disease is still unknown. The structural change is a wedge deformity of 5 degrees or more across three consecutive vertebrae³¹ (Figure 4-7). The lower thoracic or high lumbar regions are most commonly involved, and the thoracic kyphosis is typically greater than 45 degrees.³⁰,³² Individuals with Scheuermann’s disease should avoid positions or exercises that contribute to thoracic flexion. Attempts to overcorrect the thoracic flexion could result in increased lumbar extension. Patient education is important regarding the effect of anterior compressive forces on the spine and minimizing activities that would worsen the condition such as unsupported sitting, trunk curl exercises, and even various weight-training exercises. The patient should also avoid activities that require prolonged trunk flexion.

Figure 4-7 X-ray of Scheuermann’s disease.

(Courtesy of Dr. R. Cairns. From Cassidy JT, Petty RE: Textbook of pediatric rheumatology, ed 5, Philadelphia, 2005, Saunders.)

Osteoporosis is another condition that often results in a thoracic kyphosis because of vertebral compression fractures that result in wedge deformities of the thoracic vertebral bodies.⁵ The greatest risk factor for development of a compression fracture in an osteoporotic spine is a previous fracture in the same region.³³,³⁴ Kyphosis as a result of osteoporotic compression fractures has been reported to be associated with decreased function and quality of life³⁵ and an increased risk for falls.³⁶,³⁷

Posterior trunk sway of the thoracic spine occurs when the upper back is shifted backward and the hips are swayed forward so that typically the shoulders are posterior to the hip joints.²⁹ Generally, individuals with this type of posture have a long kyphosis²⁹; however, the amount and location of the thoracic flexion may vary. Posterior trunk sway results in decreased participation of the trunk extensors and an increase in the use of the RA as an antigravity muscle to control the trunk.³⁸ In this alignment impairment, a thoracic kyphosis can be masked by the change in alignment of the both the lower thoracic spine at the region of the thoracolumbar junction (posterior glide of the vertebrae) and the upper body sway behind the hip joint axis (Figures 4-8 and 4-9).

Figure 4-8 Swayback alignment.

Figure 4-9 Corrected swayback alignment.

The flat back posture is one in which the thoracic spine is straight or the degree of flexion is notably less than normal. In severe cases of a flat thoracic spine, there can be the appearance of a thoracic lordosis (Figures 4-10 and 4-11). The flattened thoracic spine can be an assumed posture or structural variation. When the thoracic spine is extended, structural changes are more likely. The individual with a postural flat back will be able to achieve some thoracic flexion. Those with a structural flat back usually cannot achieve full flexion, even with an active effort to curl the trunk.

Figure 4-10 Flat thoracic spine.

Figure 4-11 Thoracic lordosis.

There is a lack of normal rib cage contour in a structural flat back alignment, which often makes the scapulae more prominent on the thorax. The prominence of the vertebral border of the scapulae can be mislabeled as winging. Grieve³⁹ notes that a flat thoracic spine is common in individuals with a “painful stiffening” of the cervical region, as well as increased complaints of neck and shoulder pain. Individuals with a flat thoracic spine are more likely to have pectus excavatum.⁴⁰

Rotation of the thoracic spine is almost always an acquired problem that results from repeated movements in one direction. Activities requiring rotation associated with throwing or one-handed sports such as in baseball, softball, volleyball, or tennis can cause rotation of the thorax. Even less vigorous activities such as sitting at a desk and rotating frequently to one side to work on a computer or to answer the phone can also contribute to the thoracic spine becoming rotated. In these individuals, the rotation of the rib cage can be evident in the front view by asymmetry of the rib cage with the side contralateral to the rotation being more prominent. In this type of rotation, there is not the compensatory rotation in the opposite direction with the S-type curve that is the prevailing feature of scoliosis as described below. Some clinicians may refer to this form of rotation which is usually in only one plane as a functional scoliosis though most often the rib deformity is not as marked nor is the lateral flexion of the trunk present.

The last category of impaired thoracic alignment, scoliosis, is present when the thoracic spine and rib cage are rotated. Rotation of the rib cage and/or the thoracic vertebrae may be localized to a few vertebrae or can involve the whole thoracic spine.³ An asymmetrical contour of the rib cage is usually evident from a posterior view and becomes even more obvious in forward bending. The asymmetry may also be evident from an anterior view (Figure 4-12). The asymmetry of the rib cage usually causes an asymmetry in the position of the scapulae. Scoliosis can be postural or structural or a combination of both. Postural scoliosis, sometimes referred to as functional scoliosis,²⁹,⁴¹ is considered present when there is an asymmetry in the alignment of the thoracic spine or rib cage that is not fixed. Similar to other alignment impairments, postural scoliosis can be distinguished from structural based on the ability to restore symmetrical alignment. Postural scoliosis can occur as the result of an activity, such as throwing, that would habitually rotate the thoracic spine (Figures 4-13 and 4-14). In a postural scoliosis, there are no structural changes in the shape of the vertebral bodies or ribs.

Figure 4-12 Asymmetrical rib cage. A, Slight appearance and asymmetry. Note arm position in relation to rib cage and pelvis. B, Right side of rib cage more prominent than left. C, Another method demonstrating right rib cage prominence.

Figure 4-13 Postural scoliosis with right rotation of rib cage.

Figure 4-14 Throwing motion associated with right rotation.

Structural scoliosis is defined as a structural impairment of the vertebrae that affects all three planes: frontal, sagittal, and transverse³ (Figure 4-15). Structures that are affected by this asymmetry include not only the vertebral body but also the corresponding ribs and soft tissue structures. Idiopathic scoliosis most commonly presents in adolescence and is believed to have a familial pattern.⁴² The etiology of idiopathic scoliosis is believed to be multifactorial; possible contributing factors are hormones,^43-46 biomechanics,^47-50 and motor control.^51-55 Increased height and hypokyphosis, or flat spine, which potentially causes improper loading of the spine and thus asymmetrical growth patterns, have also been reported in individuals with idiopathic adolescent scoliosis.⁴⁷ Locomotor skills, including lateral step, balance strategies, and vibratory sense, have been reported as impaired in individuals with a structural scoliosis.^51-55 Currently, it remains unclear if the motor control impairments contribute to the spine malalignment or if the spine malalignment contributes to the motor control impairments.

Figure 4-15 Structural scoliosis. A, Right thoracic convexity and left lumbar convexity. B, X-ray of similar curvature. C, Forward bending demonstrating left lumbar convexity.

Rib Cage Alignment Impairments

The most common rib cage alignment impairments are rotational asymmetry or altered rib cage circumference. In the presence of either impairment, the subcostal angle will show a deviation from the normal symmetrical angle of approximately 90 degrees. Widening of the subcostal angle is often accompanied by an outward flare of the lower ribs in obese individuals or those with poor abdominal muscle tone. Overdevelopment of the pectoral muscles in an individual with poor abdominal muscle control can contribute to rib cage malalignment because every time the pectoral muscles are contracted the rib cage is elevated. Conversely, overdevelopment of abdominal musculature can result in narrowing of the subcostal margin; these concepts are discussed in the “Abdominal Muscle Length” section later in the chapter.

Obesity causes increased fat distribution within the chest and abdomen, which can lead to the long-term development of a barrel-shaped chest (Figure 4-16). Changes in trunk shape can be seen even in individuals who have lost weight.⁵⁶ This change in the contour of the chest wall may cause the scapulae to appear more internally rotated; however, overcorrection of scapular alignment should be avoided because of this change in chest wall shape.

Figure 4-16 Variations in trunk shape.

(From Frownfelter D, Dean E: Cardiovascular and pulmonary physical therapy, ed 4, St Louis, 2006, Mosby.)

Rib cage asymmetry is commonly caused by changes in thoracic spine alignment, as well as muscle length changes in the trunk and shoulder girdle. Thoracic spine rotation will create asymmetry in the subcostal angle, with one side appearing to be closer to midline than the other. As with scoliosis, subcostal angle asymmetry can be structural, postural, or both. Asymmetry of the rib cage can cause approximation of two adjacent ribs, resulting in compression of the intercostal nerves or increased tension at the rib insertion along the sternum or costal cartilage. Common conditions that could result include intercostal neuritis or neuralgia,^57-61 costochondritis,⁶²,⁶³ and slipping rib syndrome.^63-65 The alignment of the lower ribs is greatly affected by muscular interaction of the external oblique, internal oblique, transversus abdominis, and diaphragm (see the following sections, “Abdominal Muscle Length” and “Muscle Performance”).

Assessment of the upper extremity muscle length and function is needed to determine if muscle imbalance in the shoulder girdle is contributing to upper rib cage postural malalignment.²⁹

Other structural impairments of the rib cage include pectus excavatum, or funnel chest, and pectus carinatum, or pigeon chest (see Figure 4-16). When severe, these conditions can require surgical intervention. Rib cage depression compromising the heart and lungs occurs with severe pectus excavatum.⁶⁷ Cosmesis is the most common reason for surgery with pectus carinatum.⁶⁶ Both conditions commonly present with a hypokyphosis and scoliosis⁶⁷ and are theorized to occur because of overgrowth of costal cartilage.⁶⁸

Only limited information is available on conservative management of pectus excavatum and pectus carinatum.^67,69,70 Physical therapy is believed to be helpful if thoracic or chest wall pain is present in someone with either of these conditions.⁶⁹,⁷⁰ Understanding the biomechanical effect of the structural changes on movement may help guide expectations for treatment. With pectus excavatum because there is a fixed depression of the sternum, during inhalation there is insufficient sternal elevation resulting in decreased pump handle motion of the ribs.²⁹,⁵⁶ On the other hand, pectus carinatum is a deformity of the chest characterized by a protrusion of the sternum and ribs. With pectus carinatum there may be insufficient sternal and rib depression during exhalation. Thus, in both cases, there is the potential to develop a secondary ventilatory impairment as well as affect the length of the abdominal and intercostal musculature. In the case of pectus excavatum, the abdominal and intercostal muscles may be shortened, whereas in the case of pectus carinatum, they may be lengthened. Breathing exercises with emphasis on the specific mechanical deficit can be used to improve ventilatory mechanics in either case.⁶⁶,⁷⁰

Normal Sitting Alignment

Ideal sitting alignment for most people is with the spine erect and supported, the shoulders aligned over the hips, the feet supported, and the hips flexed to 90 degrees.¹,²⁹ In unsupported sitting, normally, the pelvis is in a slight posterior tilt, resulting in flat lumbar spine but relatively unchanged thoracic and cervical spinal alignment when compared to the standing position.³ Because of the variation in posture and anthropometrics among individuals, no chair or sitting surface is perfect for everyone. For example, a person with a long trunk will require a chair back that is higher than average to maintain adequate support of the spinal column. An individual with a fixed kyphosis should have extra support at the base of the chair back to support the lumbar spine and allow the thoracic spine to rest against the back of the chair (Figures 4-17 and 4-18). In this position, the thorax assumes a vertical alignment, which facilitates good alignment of the cervical spine. Note also that the support at the lumbar spine should not contribute to lumbar extension.¹ In an erect unsupported sitting position, there is a significant increase in the activity of internal obliques and thoracic and lumbar paraspinal musculature as compared to the slumped sitting position.³⁸ With prolonged slumped sitting, there is a “flexion relaxation phenomenon” that occurs in the thoracic erector spinae muscles.⁷¹,⁷² Thus, as an individual deviates from an ideal erect position to a more flexed thoracic spine, there is an increased dependence on the passive structures of the spine. Because both erect and relaxed unsupported sitting can be difficult for an individual to maintain, a chair with a back support should be used for prolonged sitting.

Figure 4-17 Kyphosis, sitting with lumbar support.

Figure 4-18 Kyphosis, sitting without lumbar support.

Impaired Sitting Alignment

Impaired sitting alignment can be the result of postural alignment impairments, anthropometric variations, and improper environmental factors, including seating surface and work-station configurations. Postural alignment impairments in sitting include a combination of excessive thoracic flexion, rotation, or extension, depending on the habits and alignment of the patient. A patient with thoracic rotation-flexion syndrome may habitually sit with the hips away from the chairback and leaning over onto the armrest. Sitting on one foot or sitting with your legs crossed is a common habit that can contribute to a postural scoliosis and thoracic rotation movement system syndrome. Sitting on the edge of the seat while maintaining the trunk in too erect a position may be noted in individuals with a flat thoracic spine and thoracic extension syndrome. Individuals with a long trunk and short arms are susceptible to leaning over on an armrest because of lack of support while sitting. Individuals with long legs may sit with their knees higher then their hips, causing excessive lumbar and thoracic flexion. Specific seating surface issues need to consider the effect on the thoracic spine. For example, a recliner or low couch may contribute to thoracic flexion. Habitually practicing the piano on a bench without back support may contribute to thoracic extension. The configuration of an office may contribute to thoracic rotation if the patient habitually turns to one side to file, answer the phone, or read the computer monitor. Treatment suggestions for correction of specific sitting postures can be found in the descriptions of the thoracic movement system syndromes and treatment.

Thoracic Spine Motion

Across the twelve thoracic vertebrae, motion is cumulative, with each segment contributing relatively small degrees of movement for each direction. In comparison, sagittal plane motion of the thoracic spine segments is more limited than in the cervical and lumbar regions. The amount of motion that is available in the upper and middle thoracic regions is limited by the ribs and sternum. The lower thoracic segments have floating ribs that do not limit mobility as much as true ribs, thus contributing to increased sagittal plane motion in the lower thoracic segments.²

During active thoracic flexion and extension, motion should be occurring in all segments; however, the distribution of motion should gradually increase from T1 to T12. Currently, it is accepted that normal thoracic flexion ROM is 30 to 40 degrees, while thoracic extension is 20 to 30 degrees with a combined ROM of 50 to 70 degrees.³ According to White and Panjabi,² for flexion and extension the contribution of motion from each segment is as follows: The upper thoracic spine (T1 to T5) contributes approximately 4 degrees of motion, the middle thoracic spine (T6 to T10) contributes approximately 6 degrees of motion, and the lower thoracic spine (T11 and T12) contributes 12 degrees of motion (Figure 4-19). According to Panjabi et al,⁷³ the PICR for flexion and extension of the thoracic spine is centered in the body of the inferior vertebrae. During thoracic flexion, there is an anterior-superior translation of the inferior facet of the superior segment, and during extension, there is a posterior-inferior translation of the inferior facet of the superior segment (Figures 4-20 and 4-21). Observation of increased motion at any segment is probably indicative of increased translation at that segment. Research related to the normal amount of in vivo motion is very limited.

Figure 4-19 Distribution of motion across each segment of the spinal column.

(Styled after White AA, Panjabi MM: Kinematics of the spine. In White AA, Panjabi MM, eds: Clinical biomechanics of the spine, ed 2, Philadelphia, 1990, Lippincott. In Neumann, DA: Kinesiology of the musculoskeletal system: foundations for rehabilitation, ed 2, St Louis, 2010, Mosby.)

Figure 4-20 A, Thoracic flexion. B, Thoracic extension.

(Modified from Neumann, DA: Kinesiology of the musculoskeletal system: foundations for rehabilitation, ed 2, St Louis, 2010, Mosby.)

Figure 4-21 Rotation.

(From Neumann, DA: Kinesiology of the musculoskeletal system: foundations for rehabilitation, ed 2, St Louis, 2010, Mosby.)

Because of the approximation of the ribs and the orientation of the facets, the amount of lateral bending in the upper and middle thoracic spine is relatively small. The upper and middle regions of the thoracic spine contribute 6 degrees of motion, whereas the lower segments T11 and T12 contribute 8 to 9 degrees of motion at each segment.² The total amount of thoracic lateral bending is 25 degrees.³ The PICR for lateral bending is centered in the lateral half of the body of the inferior nonmoving segment, contralateral to the direction of the motion.² For example, during right lateral flexion, as T8 moves to the right, the PICR will be in the left lateral aspect of T9 vertebral body.

In contrast to lateral flexion, there is a greater amount of rotation ROM available in the thoracic spine. In addition, compared to the lumbar spine, the motion of rotation is greater in the thoracic region. Total amount of unilateral rotation in the thoracic region is 30 to 40 degrees.^3,74-76 The upper and middle regions of the thoracic spine demonstrate more rotation ROM than in the lower thoracic region (see Figure 4-19). The angle of the thoracic facets allows increased motion into rotation, especially in the upper and middle thoracic region.² White and Panjabi report the following values for rotation: T1 to T10 contributes 8 to 9 degrees of motion from each segment, whereas at the thoracolumbar junction, T11 and T12 only contribute 2 degrees of motion per segment.²

Description of the PICR for thoracic rotation differs between sources depending on the study methodology. White and Panjabi’s conclusion that the PICR for rotation is located on the endplate and spinal canal of the inferior vertebrae is based on their literature review.² Most of the studies included in their review used cadavers with the rib cages removed. Molnar et al⁷⁷ used geometric modeling of the thoracic spine with ribs attached and concluded that the PICR is in the anterior portion of the spinal canal. Placement of the PICR for rotation in a more anterior location or lateral location would create spinal cord displacement, which is known as the cigar-cutting effect. Because of these relative small axes of motion, when observing the motions of lateral flexion and rotation, one should observe motion being equally distributed across each segment. Rotation of the thoracic spine should be symmetrical and maintain a relatively vertical axis with minimal lateral movement. Any significant lateral “off axis” translation observed during active thoracic rotation would be considered an impairment. Clinically, thoracic rotation is the most common cause of pain syndromes in the thoracic region.^2,78-80

The upper thoracic region is believed to demonstrate an ipsilateral coupling pattern of lateral flexion and rotation, similar to the cervical spine, whereas the middle and lower segments demonstrate an inconsistent pattern of coupling.^2,3,81 Recent investigators, however, have noted that the coupling pattern of lateral flexion and rotation of the thoracic region remains inconsistent across all regions.⁸² Generally, end-range of flexion or extension of the thoracic spine will decrease the amount of rotation that is available, resulting in compensatory lateral flexion to gain ROM.³⁹,⁷⁴ The ease of motion into flexion and anterior translation causes joint surface approximation and soft tissue tension; subsequently, either rotation or lateral flexion can cause relatively large stresses on the soft tissues in the region of the thoracic spine. A movement examination should include the observation of (1) the starting position of the thoracic spine and (2) the relative segmental contributions for rotation and lateral flexion. Based on these observed movement impairments and the effect on the symptoms, a specific treatment program can be developed.

Incidence of degeneration of the thoracic spine is relative low when compared to the lumbar and cervical spines.⁸³,⁸⁴ This difference in the thoracic region has been attributed to a relatively small PICR for the thoracic spine motions, the load-bearing capacity of the ribs, and the relative small size of the intervertebral discs.⁸³ Lower segments of the thoracic spine are the most common site of degeneration and disc herniation.⁸³,⁸⁴ Atypical symptoms related to neural compromise have been reported in individuals with thoracic herniation, including extremity, abdominal, pelvic, and chest pain.^85-92

Rib Cage Motion

During ventilation, there is a simultaneous change in the rib cage shape across three planes of motion. During maximum inhalation, there is a slight superior and posterior motion of the thoracic vertebrae causing very slight extension, as well as superior anterior expansion of the rib cage⁸¹,⁹³ (Figure 4-22). Rotation of the ribs occurs during this superior motion along a 35- to 45-degree axis from the demifacets located on the vertebral bodies and discs. During exhalation, there is a reversal of these motions. Pump-handle motion is the sagittal plane or anterior superior motion of the ribs. Bucket-handle motion is the frontal plane or superior lateral motion of the ribs. Clinical assessment of ventilatory motion should include observation of the lateral and anterior aspects of the rib cage and a posterior view of the thoracic spine. The alignment of the trunk and the flexibility of specific vertebral segments contribute to the development of common movement system syndromes. For example, during inhalation, individuals with a thoracic flexion syndrome and a kyphosis have decreased superior motion of the spine, sternum, and anterior rib cage, with an increase in the lateral motion of the rib cage. Individuals with a swayback alignment have excessive posterior motion of the thoracic spine during ventilation. Individuals with a thoracic extension syndrome with a flat thoracic spine have an increase in the superior posterior motion of the spine and superior anterior motion of the sternum and anterior rib cage. Rotation of the thoracic vertebrae causes rotation of the rib cage. Thus, in the case of scoliosis, the rib cage is asymmetrical. Asymmetrical breathing patterns are common in individuals with scoliosis and have been suggested as contributing to imbalances of the trunk musculature.⁹⁴

Figure 4-22 Ventilation. Four views: A, Subcostal angle at rest. B, Subcostal angle with inhale. C, Side view at rest. D, Elevation of rib cage with inhale.

Posterior Musculature

Anterior Musculature

Generally, abdominal muscles are recognized as having a variety of essential functions: support and protect the internal organs, assist with exhalation, and provide both stabilization and movement of the trunk. Probably less understood is what constitutes ideal abdominal performance. There is often an exaggerated emphasis on abdominal strength, especially the RA, and little attention is paid to motor control. The influence of abdominal muscle length on abdominal muscle function is often underappreciated. Assessment of abdominal muscle length, recruitment patterns, and performance are an important part of a thorough thoracic examination. Furthermore, treating patients with pain syndromes by indiscriminately issuing abdominal exercises may perpetuate their thoracic movement impairments.

Abdominal Muscle Length

Ideal abdominal muscle length promotes ideal trunk alignment. Optimal resting length of each of the abdominal muscles holds the spine, rib cage, and pelvis in the correct position. Because passive tension of the abdominal musculature contributes to postural control, the efficiency of maintaining good trunk alignment is greatly enhanced when the abdominal muscles are at ideal length. Consider the effect that a short RA muscle will have on trunk alignment. Individuals with a short RA muscle appear to have a depressed chest, and the thoracic spine will be kyphotic (Figure 4-23) or swayed posterior because the anterior thorax is pulled down toward the anterior rim of the pelvis. This is because the primary action of the RA muscle, which runs from the pubic rim of the pelvis up to the costal margins of the fifth through seventh ribs and xiphoid process, is to curl the trunk by approximating the sternum to the anterior pelvis.²⁹ In athletic populations, the RA muscle is often overdeveloped with “sit-up”-type exercises that lead to shortness or an increased stiffness of the muscle. Shortness of the RA muscle can contribute to movement impairments, as well as alignment impairments, by limiting thoracic extension; individuals may perform lumbar extension as a compensation for the lack of thoracic extension. Although the individual appears to have brought the thorax to a more upright position, what has occurred is an exaggeration of the curves in the thoracic and lumbar spines (see Figure 4-28, B).

Figure 4-23 Exaggeration of the curves in the thoracic and lumbar spines.

(From Kendall FP, McCreary EK, Provance PG: Muscles: testing and function, ed 4, Philadelphia, 1993, Lippincott Williams & Wilkins.)

As with the RA muscle, the relationship between standing alignment and length of the oblique abdominal muscles should be considered. An individual who habitually stands in a swayback alignment places the fibers of the external obliques in a lengthened position while the fibers of the internal obliques are slightly shortened.²⁹ Habitual assumption of a swayback standing posture shifts the center of mass posterior so that the abdominal muscles, RA and internal obliques muscles in particular, play a greater role in holding the upright position, acting as antigravity muscles.

The length of the internal and external oblique muscles is reflected, in part by the subcostal angle. An ideal subcostal angle of approximately 90 degrees is considered to be a reflection of balance between the internal and external obliques.¹ A subcostal angle greater than 90 degrees may indicate shortness of the internal oblique muscles or excessive length of the external oblique muscles, with the latter often the case in individuals who have poor abdominal tone. The individual who routinely has performed abdominal crunches as the main abdominal exercise would be expected to develop shortness or stiffness in the internal oblique (as well as the RA muscle). The result is this individual’s subcostal angle may be greater than 90 degrees. Contraction of the internal oblique muscles that run obliquely in the superomedial direction from the iliac crest to the linea alba and the lower ribs, pulls the thorax toward the pelvis and widens the subcostal angle. Conversely, a narrow subcostal angle could indicate shortness/stiffness of the external oblique muscles. The anterior fibers of the external oblique muscles run inferomedially from the fifth to twelfth ribs toward the linea alba, inguinal ligament, and the anterior pelvic rim. The angle of pull of the external oblique muscles decreases the subcostal angle. The upper fibers of the transversus abdominis muscle may have some ability to narrow the subcostal angle.²⁹

Another form of asymmetry commonly found in the abdominal muscles is an alteration in the resting length of the internal and external obliques on one side compared to the other. An individual who has repeatedly rotated the trunk to the right to perform work duties may develop a postural impairment of rib cage rotation to the right and shortness of the left external oblique muscle compared to the right internal oblique muscle. Additionally, the right internal oblique would be expected to be shorter than the left internal oblique. The subcostal margin would be asymmetrical so that the left subcostal margin would be closer to midline than the right (Figure 4-24). The habit of sitting on one’s foot or leaning over onto the armrest produces lateral trunk flexion, which can also lead to development of length asymmetries in abdominal muscles. The alteration of length depends on the frequency and constancy of assuming such positions, as well as what other activities or positions the individual performs to reverse the lateral trunk flexion/rotation. An individual with poor abdominal muscle tone is probably more likely to develop this postural scoliosis because they lack the normal muscle stiffness that would help to “derotate” the trunk.

Figure 4-24 Left subcostal margin would be closer to midline than the right.

Although the subcostal angle is a useful guide for determining the length of the oblique abdominal muscles, it should not be considered an absolute indicator; variations will occur between individuals because of their body structure, pulmonary dysfunction, or other conditions such as ankylosing spondylitis. The length of the oblique musculature can be assessed further by observing the movement of the rib cage and subcostal angle with inhalation and with full-arm elevation (Figure 4-25). Average rib cage expansion is 5 to 10 cm¹⁰⁶ going from maximum exhalation to maximum inhalation; with age, rib cage motion does decrease,¹⁰⁶,¹⁰⁷ so values on the lower end of normal would be expected in older individuals. Less than 3 cm change in rib cage motion would be considered impaired expansion. Expansion of the rib cage and widening of the subcostal angle during inhalation will be limited by shortness in the abdominal muscles. The limitation in motion will be greater with arms elevated overhead. Failure of the rib cage to expand is a potential sign of shortness in both internal and external oblique muscles. If the subcostal angle does not widen when the subject inhales with the arms overhead, the external oblique muscle is implicated. Limited range of motion and lateral trunk flexion toward the contralateral side may be another indicator of short abdominal muscles. Conclusions about abdominal muscle length should be based on evaluation of the patient’s age, body habitus, activity level, and movement tests.

Figure 4-25 Length of the oblique musculature can be assessed further by observing the movement of the rib cage and subcostal angle with inhalation and full-arm elevation. A, At rest with narrow subcostal angle. B, With inhalation, the angle widens. C, Inhalation with arms over the head. The angle does not widen as much as with arms at side.

Development of abdominal muscle shortness can occur by overexercising the muscles or continually adopting postures that allow the abdominal muscle to rest at a shortened length. The general public seems to be under the perception that the abdominal muscles cannot be exercised too much. However, excessive abdominal exercise can lead to muscle imbalances as described previously. The imbalance in the abdominal muscle contributes to movement impairments but may have other consequences. Shortness or stiffness of the oblique abdominal muscles can interfere with the ability of the inspiratory muscles to lift and flare the rib cage. Because the oblique muscles assist with exhalation during strenuous breathing, aerobic activity may perpetuate the muscle shortness. Importantly, an increase in the compression forces on the thoracic spine and rib cage may result from oblique abdominal muscle shortness. Some individuals may be creating greater stresses on their thoracic spine by working on abdominal strengthening exercises.

Muscle Performance

Using the term muscle performance to describe the abdominal function encompasses both parameters of strength and recruitment. Defining abdominal muscle function based only on the results of standard manual muscle testing (MMT), such as the leg lowering test, would dismiss the importance of motor control.¹⁰⁸ Stability of the spine and rib cage requires coordinated activation of the abdominal muscles. Modulation of abdominal muscle activity to meet specific functional demands is crucial for appropriate spinal stabilization. Deficits in abdominal muscle motor control have been found in subjects with low back pain¹⁰⁹,¹¹⁰; however, it is not known if similar motor control impairments exist in the thoracic spine. Furthermore, it is not clear if the alteration in muscle activation patterns is the cause or the effect of the low back pain. Although little attention has been directed at the relationship between thoracic pain syndromes and abdominal muscle performance, some insights may be gleaned from the work examining their affect on the lumbar spine, but caution is advised in attempting to generalize results across spinal segments.

One of the most important functions of the abdominal muscles is to provide isometric support to resist compensatory spinal motions during extremity motion.¹ Porterfield and DeRosa state that ideally the abdominals function as antirotators and antilateral flexors.¹⁰⁴ The anatomical arrangement of the internal and external oblique RA and the transverse abdominus muscles is such that when working optimally, they provide stability of the spine and rib cage. During extremity movements, the trunk should be a stable foundation; the abdominal muscles play a major role by countering the rotational moments placed on the thorax and spine during limb movement.¹⁰⁰,¹⁰⁴ Although the oblique muscles are thought of as rotators and lateral flexors of the trunk, their role in providing stability is achieved by resisting those rotational forces. The abdominal muscles continue to be a major source of trunk stability even when the trunk is in flexion, extension, or lateral flexion.¹¹²

During lower extremity movements, the external oblique muscles help prevent anterior pelvic tilt and work with the internal oblique muscles to prevent rotation of the pelvis. When the pelvis is stabilized, the external and internal oblique muscles should control rotation of the rib cage and thoracic spine. A common movement impairment seen in the thoracic region is rotation of the thorax during extremity motion. This impairment can be found even in individuals who do regular abdominal exercise, usually because their exercise strategies have focused on strength and not control. Treatment of the rotational impairment is accomplished by having the patient practice extremity movements while focusing on maintaining rib cage and spine stability. Often, this exercise must be started at a very low level and then progressed as the patient demonstrates the ability to control the motion. For example, a patient with pronounced weakness of the abdominal muscles and excessive flexibility in the thorax may need to start exercising by lying supine, contracting abdominals, and easily moving one arm overhead toward flexion. The patient would stop the motion of the arm when rib cage or spinal motion was detected; initially the patient may move through only a limited ROM but with continued practiced should achieve full flexion. Movements of the arm into horizontal abduction would be considered a progression because the abducted position will tend to rotate the thorax. Higher level exercises may use resistance. Exercise movements that target the latissimus dorsi or serratus anterior will require activity of the external oblique to oppose the forces on the rib cage.¹ Lower extremity motions are useful to not only assess abdominal muscle performance and stability of the thorax but also as a method of challenging the muscles.

The TA muscle is often referred to as a muscular corset. The activity of the TA muscle has traditionally been considered to be a spinal stabilizer, in part by increasing intraabdominal pressure (IAP). The role of the TA in spinal stabilization has been shown to be minimal.^110a Increasing IAP does increase spinal stiffness,¹¹¹,¹¹³ which can help prevent tissue strain.¹¹¹ Contraction of the TA muscle does increase IAP via its insertion into the lumbar fascia¹¹¹; however, its contributions to trunk mechanics may be more complex than that of a corset. The TA muscle has been shown to be active with trunk rotation¹¹⁴ and interestingly, differential activation within portions of the TA.¹¹⁵ Urquhart and Hodges¹¹⁵ used a paradigm of pelvic rotation with the thorax fixed and found that the lower and middle regions of the TA muscle were active during contralateral rotation of the pelvis and the upper fibers during ipsilateral rotation. The authors suggested several possible explanations for the apparent contradictory activity of the TA muscle: (1) stabilization of the linea alba and aponeuroses against the pull of the internal oblique or internal obliques, (2) control of the motion of the rib cage and lumbar spine via insertion onto the lumbodorsal fascia, or (3) the contraction served to increase the intraabdominal pressure.¹¹⁵ These new insights into the function of this muscle correspond to anatomical studies documenting variations in fiber direction within the TA: The upper fibers are oriented horizontally and the middle and lower fibers are angled somewhat inferomedially.¹¹⁶

Another example of regional distinction in the TA muscle was noted during arm movements: Recruitment of the upper portion of the TA muscle was delayed in response to arm movement compared to middle and lower regions.¹¹⁷ Initial investigations into the activity of the TA with extremity movement did not demonstrate differential activity of the muscle dependent on the direction of the arm.¹¹⁸,¹¹⁹ According to Hodges, the activity of the TA would not depend on the direction of force if it contributes to spinal control through modulation of intraabdominal pressure.¹¹³

The RA muscle is aligned in such a manner that it does not provide any significant control over rotation.¹²⁰,¹²¹ Therefore exercise programs that emphasize the RA muscle may lead to a compromise in the control of rotation.¹ Furthermore, RA muscle exercises are often issued with the intent of targeting either the upper or lower portion of the muscle.¹²²,¹²³ However, in EMG studies, no difference was found between activation of the upper and lower portions of the muscle during common exercise maneuvers.¹²⁴ Previous studies that may have demonstrated a difference in activity were flawed because the EMG signals were not normalized.

Treatment of thoracic pain syndromes often involves working on trunk muscle control so that both the abdominals and the posterior trunk muscles work synergistically. Instructing the patient to focus on maintaining stability of the spine, rib cage, and pelvis during extremity movements is a useful strategy aimed at improving motor control. This approach is also ideal when considering the length-tension relationship of the abdominals because performing exercises with the trunk in a neutral alignment works the abdominals at their ideal length. Stabilizing the thorax during movements of the extremities is usually easiest in supine and becomes more difficult when the patient moves into sitting, quadruped, or standing.¹¹⁷ When lying supine, the compliance of the rib cage is decreased¹⁰⁷; therefore controlling unwanted rib cage motion should be easier for the patient. Exercises can be adapted to meet the specific needs of the patient. It is worth emphasizing that patients may have the ability to generate sufficient force with their abdominals but still lack the precise control needed. The greater the demands the patient places on his or her body, the greater precision needed from the trunk muscles. For example, a competitive tennis player needs to demonstrate the ability to move the arm against resistance while maintaining spine and rib cage stability in standing. In contrast, a sedentary 65-year-old patient may only be able to move one arm up overhead without allowing the rib cage to move while in the supine position.

With nonstructural alignment impairments, the patient should actively correct the alignment and maintain the correction. This can be done intermittently throughout the day and as the patient gains endurance, the alignment correction can be held for longer periods of time. Holding the corrected position will result in the muscles working at the appropriate length. Eventually, the postural correction can be maintained with mostly passive muscle tension. As discussed earlier, thoracic pain syndromes are frequently associated with alterations in tissue properties and the development of excessive flexibility in specific directions. Although some may consider this to be mostly an arthrokinematic dysfunction, reversal of the dysfunction will best be achieved by teaching the patient appropriate trunk muscle recruitment, so the patient can limit or stop the undesired motion.

There are those patients, usually very sedentary, who are unable to readily recruit their abdominal muscles. Having these patients practice abdominal contractions in sitting or standing so that they pull in against the abdominal contents will improve their success. They may spend a week between visits practicing the isolation of abdominal contraction versus inhalation or Valsalva maneuver.

Extensive discussion of the mechanics of breathing is beyond this text; however, a review of the basic kinesiology is warranted. Contraction of the diaphragm will widen the subcostal angle and increase the chest volume as it descends toward the abdomen and compresses the viscera. The increase in chest volume is proportional to the rib cage displacement.¹²⁵ The resistance of the abdominal muscles, viscera, and the intercostals improves the efficiency of the diaphragm. Optimal performance of the diaphragm relies on a balance between the muscles of ventilation; if the resistance from the intercostals and the oblique abdominal muscles is excessive because of muscle shortness or stiffness, then the diaphragm will be required to work harder during inhalation. Conversely, lack of resistance from abdominal musculature and the intercostals also creates an imbalance that can manifest in two common patterns known as paradoxical breathing. In one pattern, when the diaphragm contracts and there is insufficient resistance from the abdominal muscles, the abdomen bulges outward, limiting the need for rib cage expansion. Such is the case with individuals with abdominal muscle paralysis; contraction of their diaphragm will cause abdominal distention rather than chest expansion. The second type of paradoxical breathing occurs when the abdomen is drawn inward during inhalation, which commonly occurs when there is weakness of the diaphragm and is seen in individuals who are ventilator-dependent.

Clinically, what can be observed in a neurologically intact person is inhalation as a substitute for abdominal muscle contraction. A common error when attempting to contract abdominal muscles by “pulling the belly in” is to inhale by contracting the diaphragm or the accessory muscles of inhalation rather than the abdominals, which are muscles of exhalation. Appropriate contraction of the abdominal muscles should flatten the abdomen, change the firmness of the external obliques, and often narrow the infrasternal angle. Treatment should include education and practice to correct the coordination impairment by having the individual gently blow outward as he or she contracts the abdominal muscles.

The traditional view of intercostal muscle function is that the external intercostal muscles elevate the ribs and therefore are considered inspiratory muscles; the internal intercostals, with fibers angled downward and dorsally, pull the ribs closer together assisting with expiration. Other authors believe that rather than opposing functions, the intercostal muscles work together to stabilize the rib cage against the pull of the diaphragm and the fluctuating pressure in the thorax.⁹⁶ This belief is supported by EMG activity of both the internal and external intercostals during both phases of ventilation.¹²⁶,¹²⁷ The anatomical location of the intercostals may explain what appears to be a dichotomy in their function. The expiratory mechanical advantage of the internal intercostals decreases moving from bottom to top of rib cage and the most anterior portion, often as parasternal intercostals, become inspiratory muscles.¹²⁸ Although the intercostal muscles are considered primarily ventilatory muscles, EMG studies have demonstrated activity of the intercostals during trunk rotation.¹²⁹ Using indwelling electrodes placed in the lateral intercostals, Whitelaw¹²⁹ demonstrated that the internal intercostals were active with ipsilateral rotation and the external intercostals were active during contralateral rotation. The activity in muscles was much greater than the activity during breathing. Although the intercostals may assist with trunk rotation, their operating range and their force-generating capacity would be less than that of the abdominals.

Symptoms and History

Individuals with the thoracic rotation-flexion syndrome complain of pain in the thoracic region, which may radiate into the lateral and anterior rib cage or abdomen. They will note an increase in pain with lying down, reaching, or trunk rotation. Ventilation is affected so that pain occurs with forceful exhalation.^134,146-148 Common recreational activities reported by individuals with a rotation-flexion syndrome include any activity that repeatedly places their trunk into flexion and rotation such as crew, squash, golf, diving, and running (asymmetrical arm swing and trunk rotation). Habitual trunk flexion with rotation during functional activities include arranging the desk so that flexion and/or rotation is required to reach the phone, computer, and files or greet incoming customers/clients. Other habits are sitting shifted to one side (leaning toward the mouse pad side of the desk), sitting on one foot, or leaning on an armrest while working, reading, driving, or watching television. Pain with sitting is reduced or abolished when the individual uses a backrest to keep the spine more erect and to avoid asymmetrical postures such as leg crossing, unilateral armrest use, or sitting on one foot. Individuals with a rotation-flexion syndrome may have a history of loss of motion at the glenohumeral joint because of a frozen shoulder or a rotator cuff injury or a history of chest surgery in which the rib cage or sternum has been surgically manipulated.

Key Tests and Signs

Movement Impairment Analysis

Standing tests

Standing trunk flexion demonstrates excessive flexion and rotation in the thoracic spine; in addition, the presence of a rib hump is more noticeable in a thoracic flexed position compared to standing. The motions of trunk rotation and lateral flexion demonstrate an asymmetry in motion and/or pain with these movements. Either motion may cause a radicular symptom into the chest or abdomen because of neural compromise at either the vertebral foramen or along the length of the ribs. Unilateral shoulder flexion, which is a test for the presence of spine motion during extremity motion, results in variation side to side. Thus, with arm motion there is a resulting motion at the spine and rib cage with or without reproduction of the symptoms. Bilateral shoulder flexion demonstrates an increase in thoracic flexion or sway with unilateral trunk rotation. In the presence of a kyphosis-lordosis alignment impairment (Figure 4-26), rotation may also be present in addition to the increased thoracic and lumbar curves. With both unilateral and bilateral shoulder flexion, pain and motion will be improved if the trunk is supported either by a wall or lying recumbent. The spine will be straighter and aided in the prevention of rotation with the extremity movement. Caution should be used when considering cueing for recruitment of the abdominal musculature for trunk control during this follow-up test, since the increased flexion and spine compression may increase the individual’s pain during arm motion. If the individual presents in an early stage of rehabilitation, protection of the thoracic spine and neural tissue can be achieved by performing supported shoulder flexion while facing the wall. Thus the weight of the upper body can be unloaded by the wall, the thoracic spine can be easily extended without overcorrection. The exercises can be progressed once the patient has advanced to a rehabilitation stage to strengthen the thoracic paraspinal muscles in the same position by active shoulder flexion or flexion without support from the wall.

Figure 4-26 Kyphosis-lordosis.

In the presence of a thoracic rotation-flexion impairment, asymmetrical motion of the rib cage will be noted during ventilation (most commonly during bucket-handle assessment of the rib cage). In addition, because of the positional impairment of sternal depression and dominance of the RA muscle, decreased pump-handle motion compared to the relative amount of bucket-handle motion will also be present.

Supine tests

Pain will commonly be reported when assuming the supine position. Accommodation of the thoracic flexion should be done by providing support for both the cervical and thoracic spine into flexion. Padding may be needed unilaterally to accommodate a structural rotation of the rib cage or spine. A follow-up test of removing some of the support after 5 to 10 minutes in the position should be done to determine if the patient can tolerate the straighter position. Examination of the subcostal margin in the supine position will reveal rib cage asymmetries and give insight in muscle length issues related to the internal oblique, external oblique, and the RA muscle. An increased subcostal margin in both standing and supine may indicate a decreased length of the internal oblique muscles and an increase in the length of the external oblique musculature. An asymmetry of the subcostal margin is commonly present in this category. Approximation of the sternum toward the pubis may be present if there is a marked shortness of the RA muscle. During testing of the abdominal musculature, there will be poor control of the oblique abdominal muscles with rotation of the rib cage and/or thoracic spine during upper or lower extremity movement. Use of inhalation to stabilize the rib cage by contraction of the diaphragm and increasing IAP instead of appropriately recruiting the abdominal musculature is commonly observed. In the presence of sway or sternal depression, increased recruitment of the RA muscle over the lateral abdominal musculature can be seen. In younger individuals, the RA muscle will test strong during trunk curling; however, rotation during the trunk curl demonstrates a unilateral weakness of the oblique abdominal musculature. Unilateral shoulder flexion in the supine position will reveal a rib cage motion or thoracic spine motion that will be most pronounced when moving the arm in a diagonal pattern. Pain with arm motion will commonly decrease with cueing to control the rotational movement by increasing abdominal muscle contraction during the motion. If the patient is in Stage 1 for rehabilitation, the recruitment of the abdominal musculature may increase pain from compressive force on the spine and rib cage. Thus caution should be used during abdominal muscle testing by monitoring closely for an increase or worsening of the presenting symptoms. Hip abduction with lateral rotation in the flexed position is commonly assessed if the individual complains of symptoms during functional activities that require leg motions such as driving and walking. Rotation of the thoracic spine and rib cage and pain noted during the leg motion will be reduced by cueing to recruit the trunk musculature during the activity. Both the thoracic spine extensors (control flexion) and the abdominal musculature (control rotation) may need to be recruited for adequate trunk control during upper and lower extremity motions.

Prone tests

Prone-lying may reduce symptoms in younger more flexible individuals with a thoracic rotation-flexion syndrome. However, older individuals may need increased support in prone to accommodate the amount of thoracic flexion that is present. In the case of a severe kyphosis, prone should not be attempted. Prone lying may also require some lateral trunk support to minimize rotation while in this position. As in the supine position, removal of some of the trunk support can be done after 5 to 10 minutes to see if the individual can tolerate a more extended position of the spine.

Trunk extension in the prone position will test weak in older individuals with a thoracic flexion alignment impairment^149-152; however, use of this position for testing and exercise should be done with caution because the erector spinae musculature is not isolated to the thoracic region. Recruitment of the erector spinae in the prone position increases both lumbar and thoracic region extension. Because of the high prevalence of osteoporosis and osteoarthritis in older individuals and the mechanical advantage of the lumbar paraspinals to compress the lumbar region, low back pain may occur during prone trunk extension. If not properly positioned into lumbar and thoracic flexion, an imbalance between the strength and control of the upper thoracic paraspinals (weak and decreased recruitment) compared to the lumbar paraspinals (strong and increased recruitment) can worsen the compression forces at the lower rib cage and thoracolumbar junction.

Single arm raises in the prone position in individuals with a thoracic rotation with extension syndrome can reveal thoracic rotation. Cueing to increase paraspinal muscle recruitment aids in the flexion and rotation control that commonly decreases symptoms. In an individual who is unable to tolerate unilateral arm motions, bilateral symmetrical scapular adduction with shoulder abduction (hands on head, elbows flexed, and elbows extended) can be performed in the various degrees of difficulty.

Quadruped tests

When positioned in the quadruped position, there will be a noticeable amount of thoracic flexion with rotation of the rib cage (hump). Quadruped is commonly a pain-relieving position for individuals with thoracic rotation with flexion because the thoracic spine is suspended between the upper and lower extremities, thus providing a position of unloading. Because of upper extremity muscle weakness and rib cage asymmetries, scapular winging or tilting is commonly present. Rocking back in the quadruped position will reveal an increase in thoracic flexion and rotation. Cueing is needed to relax the abdominal musculature during the rocking motion to prevent flexion of the thoracic spine. Shoulder flexion in quadruped can cause rotation of the thoracic spine and rib cage. Instruction to recruit the latissimus dorsi and thoracic back extensors by an isometric contraction (isometric shoulder extension of the weight-bearing arm toward the ipsilateral knee) reduces the rotation. Inability to perform this correctly in the quadruped position should prompt the therapist to downgrade the activity by performing unilateral shoulder flexion in the prone position. In very active populations, crawling can be assessed to create a more unstable activity that requires trunk rotation. Crawling in individuals with thoracic flexion with rotation will reveal an asymmetry in the trunk rotation.

Symptoms and History

In this syndrome, the pain in the thoracic region usually increases when reaching with both arms, lying in the supine position or when trying to straighten the thoracic spine after prolonged flexion. Ventilation will be affected so that pain occurs with forceful exhalation.^134,146-148 Individuals with a flexion syndrome often participate in activities that cause flexion such as bending to garden, prolonged reading, or watching television. Habitual trunk flexion during functional activities is commonly observed in individuals with this syndrome. These individuals sit slouched (leaning toward the mouse pad) or with their hips not fully back into the seat. Pain with sitting is reduced or abolished when the individual is instructed to use the backrest of the chair to keep the spine straight or support the trunk by using the armrests on the chair. Younger individuals with a flexion syndrome report a history of excessive abdominal strengthening exercises. In addition, the current postural trend for students is to sit in thoracic and lumbar flexion.

Key Tests and Signs

Treatment

Treatment of osteoporosis includes load-bearing exercises to stimulate bone growth.¹⁵⁶ Weakness of the back extensors is common in individuals with an osteoporotic kyphosis,¹⁰,¹² thus exercise prescription should include strengthening exercises for the thoracic paraspinal musculature. Consideration should be given to the biomechanical stresses applied to the adjacent spinal regions when developing a strengthening program for the thoracic back extensors. Classically, a prone trunk extension exercise is prescribed to improve the strength of the paraspinal musculature in this population¹⁵² (Figure 4-27). Careful observation of the spine during the prone extension exercise is critical for determining the region of the spine that is moving. Commonly, lumbar extension is performed to a greater extent than thoracic extension, thus increasing the compressive forces at the lumbar spine resulting in pain¹⁵² (Figure 4-28). An alternative to the classic back extensor strengthening exercise is to exercise in a functional position. Sitting and standing with the spine aligned against a wall improves alignment and unloads the weight of the upper trunk. Motions of the upper extremity, shoulder flexion or abduction, can then be used to facilitate contraction of the paraspinal musculature¹⁵⁷ (Figure 4-29). Spine compression and abdominal muscle shortness are contributing factors to the osteoporotic kyphosis, thus deep breathing while appropriately aligned on the wall should be done to increase abdominal muscle length¹,²⁹ and decompress the thoracic spine.⁹³ Because of the compressive forces on the spine with contraction of the abdominal musculature, care should be taken with strengthening abdominal muscle in individuals with osteoporosis. Generally, patients with a swayback alignment of their trunk are cued to contract their abdominals only enough to hold a corrected alignment of their trunk, while patients with a kyphosis are advised to avoid abdominal muscle contraction in standing.

Figure 4-27 Starting position for prine arm lifts. A, Insufficient support under thorax allows thoracic extension. B, Increased support places thoracic spine in more ideal alignment.

Figure 4-28 A, Kyphosis. B, Lumbar extension greater than thoracic extension. C, Improved thoracic alignment without lumbar extension.

Figure 4-29 Back to wall shoulder flexion.

Older individuals with a total C-curve of both the thoracic and lumbar spines, as well as a flat abdomen, have excessive abdominal muscle activity and markedly diminished back extensor activity. Even in the prone position, while performing shoulder flexion from the overhead position, the abdominal muscles contract rather than the back extensor muscles. Every effort needs to be made to change this recruitment pattern. Therefore these individuals need to avoid any type of abdominal muscle exercise and standing in the swayback position that makes the abdominal muscles the antigravity muscle group.

Symptoms and History

The thoracic rotation-extension syndrome causes pain in the thoracic region that may radiate into the lateral and anterior rib cage or the abdomen. Symptoms may be pain, numbness, or burning. Trunk extension and/or rotation produce symptoms so that motions of unilateral shoulder flexion or reaching are painful because of these associated trunk motions. Similarly, a deep inhalation can cause pain because of associated thoracic rotation-extension.^133,145,158 Positions and alignments that cause rotation or extension forces on the thoracic spine, such as sidelying or sitting up in an exaggerated position of trunk extension, can also cause pain.

Racquet sports, gymnastics, and ballet are activities that may have contributed to the development of the rotation-extension syndrome. Occupations that require working with the arms overhead can also contribute to the development of the syndrome. Patients with the diagnosis of thoracic rotation-extension may report a history of loss of motion at the glenohumeral joint. The loss of glenohumeral motion could cause the patient to substitute thoracic spine motion of extension and/or rotation as a substitute for loss of motion at the shoulder joint.

Key Tests and Signs

Often, patients with this syndrome have asymmetry in the thoracic spine and rib cage. The malalignment may be localized over a few segments or a structural scoliosis. From a posterior view, the spinous processes of the thoracic vertebrae may demonstrate lateral curvature and a rib hump may be present. If the rotation malalignment is in the upper thoracic region, the rib hump may not be obvious because of the scapulae; however, scapular asymmetry is likely. Loss of the normal thoracic sagittal curve is apparent in the posterior view in a few segments or the entire thoracic spine, and often the scapulae appear to wing because of the loss of the normal thoracic curve. Patients who habitually hold their spines in extension can often lessen their symptoms by relaxing thoracic paraspinal muscles and allowing the thoracic spine to flex. Minimal or no change in the thoracic curve will occur when the flat thoracic spine is structural.

From the anterior view, the chest or rib cage may be asymmetrical. The subcostal margin is often flared outward more on one side than the other. The subcostal angle may be wide (>110 degrees), and the rib cage appears to be flared. In such patients, the abdominal muscles will not be stiff or strong enough to counter the pull from the pectoral muscles so overhead movements of the upper extremities cause the rib cage elevation and thoracic spine extension.

Treatment

The treatment emphasis of the rotation-extension syndrome is to prevent extension and/or rotation motions of the thoracic spine in all positions and during motions of the trunk and the extremities. The patient’s daily routines and habits, such as sitting positions and body language, should be reviewed and observed to identify contributing factors. Those activities that the patient reports as painful are especially important to simulate in the clinic. For example, if the patient reports pain with running, observation of his or her running pattern will probably reveal asymmetrical arm swing and thoracic extension. The patient should correct this by allowing the thoracic spine to move toward flexion and limiting the arm swing.

Commonly, patients with the diagnosis of thoracic rotation-extension need to be cued to relax their thoracic paraspinal muscles and allow the thoracic spine to slightly flex. This extension posture is usually seen in both standing and sitting, but the position of rotation or lateral flexion occurs more often in sitting than standing. An example is the receptionist who sits erect in her chair and rotates to greet people as they approach her from the side. She should be cued to use the backrest on her chair and allow her trunk to relax into the chair and rotate the chair rather than rotating in her thoracic spine. When sitting, patients also need to refrain from leaning over onto an armrest or sitting on one of their legs that is bent under them.

Exercise Program

The home exercise program should focus on balance of trunk muscle activity, which often necessitates avoiding strengthening the trunk extensors. Frequently, the performance of the abdominal muscles is not optimal, so improving the strength and recruitment of the obliques is indicated. Abdominal activity is beneficial to help control the rotation forces on the rib cage and spine, as well as help balance the paraspinal activity; some patients seem to maintain spinal stability by excessive paraspinal muscle activity. Unilateral arm or leg movements are good exercises for recruiting the abdominal muscles to control the rotation of the trunk and to counter the extension of the thoracic spine.

Prone exercises are also useful for learning to control rotation and extension motions of the thoracic spine. Initially, the patient may need to lay over two pillows to position the thoracic spine in flexion (see Figure 4-27); eventually they can work toward using only one pillow under their chest. Prone unilateral arm movements, such as sliding the arm along a surface toward shoulder flexion or arm lifts, are often more challenging for patients than arm diagonals in supine and therefore should be monitored closely. To effectively stabilize the thorax during the exercise, the patient should be cued to make their trunk stiff and to activate their abdominals.

Quadruped rocking back is also a useful exercise, with the focus on controlling the motion so that the thoracic spine is not rotating or extending as the patient rocks backs. Often, the patient will flex both lumbar and thoracic spines rather than isolating the flexion to thoracic region. It may be helpful to provide manual contact over the posterior lumbar area to promote neutral spine position and gentle pressure at the sternum to promote slight thoracic flexion. A more challenging exercise in the quadruped position than rocking backward is unilateral shoulder flexion. If the patient is unable to control thoracic extension or rotation with the hips at 90 degrees of flexion, increasing the hip flexion angle during the unilateral shoulder flexion makes it easier to perform.

As mentioned earlier, compression may be an underlying source of symptoms with this diagnosis, as well as the others. Positioning strategies taught to the patient include sitting with arms supported on armrests or pillows or a lap board on the patient’s lap to help alleviate the compression. The patient may find it helpful to face the wall and rest his/her hands and forearms on the wall at head level, the emphasis is to let the upper extremities help support the weight of trunk and reduce the activity of the posterior thoracic muscles (Figure 4-30, A). Additionally, the quadruped and recumbent positions are useful in decreasing the compression of the spine.

Figure 4-30 A, Sliding hands up the wall to perform shoulder flexion. B, At maximum flexion, the patient lifts the hand off the wall by posteriorly tilting and externally rotating the scapula.

Symptoms and History

Individuals with the rotation syndrome complain of pain in the thoracic region, which may radiate into the lateral and anterior rib cage or abdomen. They note an increase in pain with reaching or trunk rotation. The most common recreational activities reported by individuals with rotation syndrome include any activity that repeatedly places their trunk into rotation, including tennis, softball, sailing, squash, and running (asymmetrical arm swing and trunk rotation). Habitual trunk rotation during functional activities are commonly observed in individuals with this syndrome and include arrangement of their desk so that rotation is required to reach the phone, computer, or files and/or to greet incoming customers/clients; sitting shifted to one side (leaning toward the mouse pad side of desk); sitting on one foot; or leaning on an armrest while working, reading, driving, and watching television. Pain with sitting is reduced or abolished when the individual is instructed to use the backrest to keep the spine straight and to avoid asymmetrical postures, leg crossing, unilateral armrest use, and sitting on one foot. Commonly, individuals with a rotation syndrome report a history of chest surgery in which the rib cage or sternum have been surgically manipulated.

Symptoms and History

Individuals with thoracic extension syndrome have an altered flexibility of the thoracic spine so that extension occurs too easily. Thoracic extension occurs most often in the interscapular region but can occur in the lower thoracic segments or the thoracolumbar junction. The symptoms associated with thoracic extension syndrome are usually confined to these same areas; however, patients may have a greater distribution of their symptoms. According to Bogduk,¹⁵⁹ pain from the thoracic spine is quasisegmental; the location of pain may be representative of the source of pain with an accuracy of one to two segments.

The habit of holding an erect posture in both sitting and standing is characteristic of individuals with this syndrome, and both positions are associated with pain. The habitual contraction of the spinal extensors contributes to altered flexibility in the thoracic spine so that extension occurs too easily. This syndrome occurs more commonly in younger rather than older people, especially those who participate in dance or gymnastics and who work with their arms overhead.

In some patients, the entire spinal column is flattened so that all of the normal curves of the spine are decreased. The upper thoracic spine, most often between the scapulae, may actually appear to be in some extension. The ability of the thoracic spine to extend may be related to some anomaly of the thoracic vertebrae. Normally, extension is limited by the superior facet impinging onto the vertebrae below, as well as the contact of the spinous processes. Because this syndrome is often associated with overactivity of both thoracic paraspinals and scapular adductors, an impairment of scapular adduction can be present as well.

Key Tests and Signs

The key tests for thoracic extension syndrome are as follows and are listed in the order they are performed during the examination.

Treatment

The treatment priority for thoracic extension syndrome is to restrict movement of the spine into extension during the patient’s activities. This will be most effective if the patient learns to recognize spinal extension and the extremity movements that induce extension moments on the thoracic region. For example, if the patient routinely has pain associated with styling her hair because arm elevation induces thoracic extension, then it is necessary to teach the patient to hold gentle flexion in the thoracic spine while elevating the arms.

Patients with the diagnosis of thoracic extension syndrome typically exhibit habitual thoracic extension. Instruction to relax the thoracic paraspinals and slightly flex the thoracic spine improves symptoms. Initially, pain will be an indication of faulty positioning; however, long-term management requires that the patient develop an awareness of spinal posture.

If compression is contributing to symptoms, positioning strategies, such as sitting with arms supported, are encouraged. In standing, the patient can help reduce compressive forces by resting the hands and forearms on the wall at head level and relaxing the trunk, so that the upper extremities help support the weight of trunk and reduce the activity of the posterior thoracic muscles. Recumbent positions or quadruped are frequently pain relieving and should be used to help control symptoms.