To achieve the elegant balance of flexibility and stability that the human spine offers, the design requires 7 cervical, 12 thoracic, 5 lumbar, and a fused set of sacral and vestigial coccygeal vertebrae. The stability comes from the fact that the spinal column is actually three columns in one. The anterior column is composed of the anterior longitudinal ligament and the anterior portion of the vertebral body. The middle column is made up of the posterior wall of the vertebral body and the posterior longitudinal ligament. The posterior column is formed by the posterior bony arch, which consists of the transverse processes, facets, laminae, and spinous processes. Each vertebra has the potential for six degrees of freedom (Fig. 34-3): translation in all three axes of movement and rotation around each axis. However, all vertebrae are not created equal. Movement at different levels of the spine is limited in some planes. In essence, in the function of the spine follows its form (with apologies to Louis Sullivan). The cervical vertebrae have the greatest freedom including free flexion, extension, lateral rotation, and lateral flexion (this is fortunate, since this freedom affords the eyes and ears a wider field of function). This mobility is due to larger disks, concave lower and convex upper vertebral body surfaces, and transversely aligned facet joints. Thoracic vertebrae have restricted flexion and extension and limited rotation but freer lateral flexion due to their attachments to the rib cage, smaller disks, flatter vertebral body surfaces, frontally aligned facet joints, and overlapped spinous processes. The lumbar spine has good flexion and extension and free lateral flexion due to large disks, posteriorly directed spinous processes, and sagittally directed facet joints. However, there is only limited lateral lumbar rotation due to facet alignment (Fig. 34-4).

The intervertebral disks form one fourth of the total length of the spinal column (11). Since they are a viscoelastic tissue, they serve as shock absorbers and take part of the load applied to the spinal column. They also redistribute the load applied on the vertebral bodies, moving more of the force to the stronger, cortical bone (arranged in parallel with the length of the spine) at the vertebral end plates than the thinner layer of cortex sandwiched between softer cancellous (and therefore weaker) bone in the center of the vertebral body. The disks also help connect the vertebra. And, as implied above, they participate in the articulation of the spine.

A number of ligaments also help to link the spine together. The anterior longitudinal ligament is a thick, strong ligament that stretches from the occiput to the sacrum along the anterior surface of the vertebral body. It attaches to the vertebral end plates and is confluent with the anterior portion of the annulus fibrosis of the disk. At the posterior aspect of
the vertebral body, there is a similar ligament, the posterior longitudinal ligament. However, it has an hourglass shape and is thinner than the anterior ligament. There are also three ligaments which connect portions of the posterior column of the spine. The supraspinous ligament stretches across the tips of the spinous processes while the interspinous ligaments stretch from one spinous process to the next. The ligamenta flava (flava is Latin for yellow and the ligament is that color due to the high proportion of elastic tissue within it) connect the laminae of adjacent vertebrae from the anterior surface of the proximal lamina to the posterior surface of the distal lamina. They also blend in with the capsule of the zygopophyseal joints.

The spine has two primary joints. The intervertebral joints (as noted above) are formed by the surfaces of the vertebral bodies with the disks. These joints (with the restrictions noted above in the discussion of vertebral anatomy)
allow limited movement in all six directions, although each individual joint only moves to a small degree. The zygopophyseal joints are the only true synovial joints in the spine and are found at the junction of the pedicle with the lamina. The form of their alignment contributes significantly to the functional movement at different levels. The transverse alignment in the neck permits good flexibility in all planes. In the thoracic spine, the facets are aligned frontally which, along with the linkage to the rib cage, limits flexion and extension. The lumbar facets are arranged sagittally, limiting lateral rotation.

It would be possible to place a spine consisting of only its bony and elastic tissues on a base and have the spinal column statically balance in an upright position. However, if the point of the flexibility of the spine is to give humans the freedom to move on two legs, then the spine requires a complex system of dynamic control. The neuromuscular system provides this balance, actuated via muscles intrinsic and extrinsic to the spinal column. The paraspinal muscles are a series of layers of longitudinal muscles attached from the occiput to the sacrum. They are partially distinguishable by their fiber direction and length but “from a functional standpoint, there is little reason to subdivide the back musculature in any detail since the muscles work together in large groups” (11). They serve primarily as extensors to resist the pull of gravity in sitting and standing. In addition, the superficial layers will produce ipsilateral rotation when firing unilaterally, while the deeper groups will produce contralateral rotation with unilateral firing. The primary lateral flexors of the trunk are the quadrati lumborum and oblique abdominal muscles. The primary flexors are the psoas, assisted by the recti abdominus.

Like every other medical condition, most of the diagnosis can be made just by taking a good clinical, functional history and performing a physical examination. “As each symptom is given, it should be pursued with a dogged tenacity until all the details are known” (12). We have mentioned that the majority of patients with scoliosis have an idiopathic condition. It is critical to first rule out spinal deformity associated with another disabling condition. Much of this will be accomplished with good history taking which can then direct and focus the physical and radiological examinations.

The first clue to the etiology of the deformity will be the age of onset. If the scoliosis presents at or soon after birth, it is more likely to be associated with a congenital bony deformity or inherited disease involving the neuromuscular system. If the scoliosis begins in late childhood or adolescence, it is likely to be idiopathic. Spinal deformity that begins in young adulthood is most likely due to trauma or infection; in middle age or later, it is likely to be associated with degenerative disk or joint disease and/or osteoporosis.

It is also important to determine if the onset of the curve is associated with any acute problem such as trauma or infection. The degree of curvature and how fast the size of the curve increases also offer insights into etiology. An underlying neuromuscular or ligamentous condition may promote quicker progression. Children within their adolescent growth spurt may have greater progression due to the rate of overall growth. Progression in an older adult may be an indicator of poor bone health.

Details relating to the nature of the curve itself are insufficient to advance the development of a good diagnosis and rational treatment plan. It is vital to inquire about associated complaints, signs, and symptoms. A thorough review of systems should be performed. However, certain areas of inquiry are more likely to yield clues. Although pain is associated with spinal deformity in adults, it is uncommon in children and adolescents (13) and obligates the physiatrist to search for underlying pathologies including neoplasm or infection. Similar to other pain-evoking conditions, details about the quality, intensity, and temporal and spatial parameters of the pain will help distinguish among bony, soft-tissue-based, and neuromuscular-based pain. Cardiopulmonary dysfunction is the most serious morbidity of spinal deformity. Therefore, questions about fatigability, shortness of breath, palpitations, and decrease in endurance must be included in the history. Any suggestion of cardiopulmonary dysfunction should lead to a more rapid and aggressive workup.

It is important to inquire about the symptoms of central nervous system dysfunction. Problems with loss of balance or falls may indicate a coordination problem such as is seen in cerebellar syndromes. Complaints of muscle spasms may indicate spasticity. Conversely, complaints of weakness or sensory loss may indicate peripheral nervous and/or muscle pathology. Reports of frequent joint sprains may indicate the presence of a condition associated with ligamentous laxity. In children and adolescents, it is important to obtain a history of developmental milestones. Indication of delay in any of the developmental spheres—social/behavioral, communication and cognition, fine motor, gross motor—may provide clues to the presence of an underlying syndrome. Since spinal deformity may be initiated or exacerbated by conditions affecting other areas of the body, the physiatrist should ask about conditions that may affect the lower limbs, such as a history of hip dislocation or leg length discrepancy, and even conditions associated with asymmetry of the upper limbs and head.

Last, but certainly not least, a thorough social and functional history must be obtained. Further clues into etiology may be gleaned. In addition, the insights obtained will identify the barriers to successful functional outcome to the treatment plan and ensure that the goals of the rehabilitation team are in concert with the goals of the patient and his or her family. In some cases, it may be beneficial to use a standardized questionnaire to follow the impact of the person’s spinal deformity on the function and related aspects of quality of life. There
is a validated instrument focused specifically on persons with spinal deformity (14, 15, 16). Alternatively, one of the many generic “disability/burden of care” or “health-related quality of life” instruments may be used (see Chapters 11 and 18).

Although school screening programs for idiopathic scoliosis may only look at a child’s spine, it is not sufficient for a physiatrist to limit the assessment of spinal deformity to the spine. A comprehensive physiatric examination must first be done. This should include assessment of pain, strength, endurance, sensation, balance (in sitting and standing), coordination, range of motion, reflexes, mobility, and dressing skills. Leg length discrepancy should be assessed, which is not always easy to determine, and corrected.

Once the general examination has been completed, a more focused assessment of the spine must be performed. You do not have Superman’s x-ray version; clothing must be removed so that the spine can be observed directly. The surface anatomy should be viewed in both prone and side lying. If the patient can sit, then the spine must be seen in sitting. If he or she can stand, even with support, then the spine must be viewed in standing. If there is concern about leg length discrepancy and/or pelvic asymmetry, the spine should also be viewed in standing with leveling blocks under the foot on the “short” side and the depth of the correction recorded. Any difference in the shape or degree of curve in different positions should be noted, it is a sign of the degree of flexibility of the curve. The spine should be viewed from both the frontal and sagittal planes. The spinous processes should be palpated to better appreciate the curves’ dimensions, including shape in both frontal and sagittal planes and presence of rotation. The curve should be described by its length (approximately which vertebrae start and end the curve), its shape (e.g., “C” or “S” shaped), and the direction of the vertex of the curve. Truncal range of motion in all planes—forward flexion, rearward extension, R & L lateral flexion, and R & L lateral rotation—should be viewed with special attention to asymmetry and spinal levels where movement is occurring. While the patient is flexing forward, the examiner should look at the shape of the rib cage for prominence or humping (Adam’s forward bending test (17), which is the test used in school screenings) (Fig. 34-5), which may be a sign of a rotatory component to the curve. The shape of the rib cage should be viewed from all angles to look for deformity. Rib cage deformity may not only be a sign of rotation of the vertebrae but also suggest underlying pathologies such as osteogenesis imperfecta. One must look not only at rib prominence but also for deformities such as pectus carinatum or excavatum. Symmetry at the top and bottom of the trunk should be assessed in sitting and standing. Shoulder
symmetry should be viewed at the level of the acromioclavicular joint (13). Pelvic symmetry can be viewed either at the brim of the pelvis at the iliac crests or at the posterior superior iliac spines, which is seen on the surface of the buttocks as the two sacral “dimples.”

Measurement of symmetry of the appendicular skeleton and head should be done to rule out asymmetries. Head size and alignment should be viewed since reports have associated these issues with scoliosis (18). There are reported associations between upper limb deficiency and scoliosis (19, 20, 21), and, anecdotally, it has been associated with neonatal brachioplexopathy (Erb’s palsy). Therefore, upper limb asymmetries should be assessed. Upper limb length should be measured in a consistent manner. One method is to measure from the acromioclavicular joint to the radial styloid. Lower limb discrepancy produces functional scoliosis in standing and it may contribute to the development of fixed scoliosis, as well (22). Lower limb length is commonly measured from the anterior superior iliac spine at the pelvis down to the medial malleolus. The physiatrist must also look for functional asymmetries that could result from joint contractures or deformities (especially at the hips and knees) or tendon contractures (especially tendons of two joint muscles such as the hamstrings and gastrocnemius). Functional asymmetry may also result from asymmetric neurological function including hemiparesis.

The standard technique for measuring the angle of a spinal curve is called the Cobb angle (23). Initially developed as a frontal plane measurement, the technique can also be used for assessing sagittal curves. We will review the method for assessing scoliosis, but the rules can be applied similarly in lordosis and kyphosis. The film from which the curve is viewed should, if possible, include the entire spine on one film and be taken posterior-anterior (to reduce the dose of radiation to the breast) (13). Even if the patient is only suspected of having a frontal curve, a lateral film must also be obtained to better assess the amount of rotation in the curve. If at all possible, the films should be done in standing. If the patient is unable to stand, then sitting is preferred to a supine film. The P-A film should be taken with the arms at the side; the lateral film should be done with the arms at 90 degrees of abduction to keep the upper limb from obscuring the spine. Although it is common to shield the perineum when films are done, the initial films should be done without gonadal shield in order to fully visualize the hips, pelvis, and proximal femurs (13). In children and adolescents, a sense of skeletal maturity can be gleaned by looking for Risser’s lines at the crest of the pelvis.

To perform the Cobb measurement, the examiner should first note the upper border, lower border, and vertex of the curve. The curve is classified by the position of the vertex into thoracic, thoracolumbar (vertex at the thoracolumbar junction), or lumbar. The upper and lower borders are identified by the “end vertebrae.” They are the first and last vertebrae that tilt into the concavity of the curve (13). To define the angle, a line is drawn on the radiograph parallel to the upper end plate of the upper end vertebra. A second angle is drawn parallel to the lower end plate of the lower end vertebra. In most cases, these lines will not intersect on the film and, therefore, the angle cannot be measured directly. Instead, using principles learned in high school geometry, a line perpendicular (90 degree angle) to each of the above lines is drawn. The angle formed by the intersection of the perpendicular lines is equal to the angle made by the upper and lower end vertebrae and is measured and reported as the Cobb angle (Fig. 34-6).

More and more facilities are converting to filmless, computer-based radiological information systems. Many of these systems offer tools to directly measure the Cobb angle on the screen. The semimanual methods still require the clinician to place the parallel lines at the top and bottom of the curves. Studies have shown these methods to have precision and
reliability similar to the film-based method (24, 25, 26). More recently, some systems have introduced fully automated Cobb angle calculations. However, it appears that this technology still requires further refinement to achieve adequate accuracy for curves of all magnitudes (27).

As mentioned above, the spine has six degrees of freedom, including rotation along the axis of the spinal cord. Many spinal curves are associated with rotation of the vertebrae. Curves with rotation may be more difficult to treat and may cause greater disturbance to the rib cage with resultant adverse effects on respiration. Therefore, it is important to assess the presence and degree of rotation associated with the curve, as well as its rate of progression. Radiographically, the position of the pedicles provides the best sense of degree of rotation on a plain x-ray. The examiner should note the symmetry and alignment of the pedicles in the P-A film. If asymmetry is present, the pedicle that is more prominent will indicate rotation away from that side of the vertebra. The degree of rotation can be graded using the system of Nash and Moe (13) (Table 34-2). Automated computerized systems to assess rotation are also under development (28).

New computer-assisted techniques are also under development to supply additional information about the three-dimensional characteristics of the curve using the data supplied by digitized plain films (29). Such information may be useful in assessing the results of nonoperative and for planning operative treatments. Despite the additional radiation dosage,
three-dimensional CT may be useful, especially in congenital disorders (30, 31). MRI might offer similar information without radiation exposure (although still with the need for sedation in groups including young children and adults with claustrophobia); however, at the current state of technology, recommendations for its use are still limited to ruling out potential etiologies or neurological abnormalities (32). It is also important to remember that neither CT nor MRI is able to assess the impact of gravity on a curve, since both studies are done in a supine position.

It should be obvious by now that among the etiologies of spinal curves are conditions intrinsic to the bone. Most of these will become evident upon careful inspection of the radiographs obtained to determine the magnitude of curvature. The spinal elements should be inspected for signs of hemivertebra, unsegmented bars, and/or bifid spinous processes (see Fig. 34-10 later in this chapter). The ribs should be viewed to look for asymmetry or changes in the natural curve (Fig. 34-7). The pelvis should be examined for signs of asymmetry (Fig. 34-8). The hip joint should be examined for signs of subluxation. Femurs should be assessed for any asymmetry and separate femur films ordered if there is any suspicion of pathology.

Pain may be the presenting symptom of spinal deformity; it is in 40% to 90% of adult scoliosis (33). In thoracic kyphosis caused by Scheuermann’s disease, it is an early symptom in 20% to 60% of patients. However, before attributing pain to idiopathic or degenerative etiologies, it is vital to remember that pain may be the sentinel of a critical, even fatal illness. Pain may be the presenting symptom in infectious processes such as epidural abscess or disciitis (34). Rarely, one can have a spontaneous epidural hematoma of the spine. In these cases, due to nerve irritation, the pain may be radicular in character. Of greatest concern is to rule out pain due to tumor. In benign
tumors, the delay between the onset of symptoms and the diagnosis can be up to 19 months. In malignant tumors, it can be up to 4 months between symptom onset and diagnosis. It is important to recall that tumor-related pain is often worse at night and is disassociated from any obvious initiating or exacerbating factors (35).

Chronic pain plays a role in many spinal curvature pathologies. As implied above, it is common in degenerative spine conditions with associated curvature. More than 50% of patients with Scheuermann’s disease have pain later in their course, especially if L1 and L2 are involved (36). There appears to be an increased risk of pain in adults who had scoliosis in childhood or adolescence (37). Pain is often a problem in persons with achondroplasia and is felt to be associated with the mechanical disadvantage of the lordosis on sagittal spinal alignment. Back pain is also found in osteogenesis imperfecta. The pain in osteogenesis imperfecta may also be related to the mechanical disadvantage of the lordosis.

As noted above, normal spine function is a delicate dynamic balance between rigidity and flexibility. It is not surprising, then, that balance may be affected by spinal deformity. When the patient has an underlying neuromuscular condition, the spine asymmetry is likely to exacerbate the difficulties with balance control. What is more unanticipated is that balance is disturbed in idiopathic scoliosis as well. Reports have shown increased amounts of sagittal and lateral sway in standing, along with increased sway radius, leading to decreased stability in standing (38). This may result in increased losses of balance and falls as well as increased and asymmetric stress on lower limb joints, creating the potential for a vicious cycle. Recent reports suggest that there may be subtle underlying neurological deficits in persons with idiopathic scoliosis manifesting as balance difficulties (39, 40).

The most critical of all of the potential complications associated with spinal deformity is compromise to the cardiopulmonary system. There is a common pathway toward cardiopulmonary dysfunction. It begins with restrictive lung disease resulting from deformity of the bellows mechanism formed by the rib cage, thoracic spine, and diaphragm. On pulmonary function testing, this is demonstrated by greater decreases in vital capacity than residual lung volume (41). In untreated idiopathic scoliosis, it has been shown that once curves achieve an angle of 70 degrees there will be a mild decrease in vital capacity. By the time a curve reaches 90 to 100 degrees, the patient with have dyspnea on effort. With curves greater than 100 degrees, alveolar hyperventilation, CO₂ retention, pulmonary hypertension, and right-sided heart failure are seen (37, 41). At this point, the patient may be irrevocably set on a downward slide of illness leading to death due to pneumonia and/or heart failure. It is likely that these problems will present with much smaller curves when there is also an underlying neuromuscular disease or syndrome affecting other organ systems. Prevention of serious cardiopulmonary decline is one of the major indications for surgical correction. Close monitoring of pulmonary function tests is an essential part of ongoing follow-up of any patient with spinal deformity, especially if progression is noted. It is quite important to remember that there is a “window of opportunity” in progressive curves and that surgery in such curves must be done before pulmonary function has deteriorated to such a degree that the risk of inability to wean from mechanical ventilation after surgery is greater than the potential benefits of the surgery.

A physiatrist is obligated to approach his/her patient holistically. As with any other disability, the emotional impact of spinal deformity should be addressed. Spinal deformity has traditionally had tragic, negative connotations in Western society as evidenced by Shakespeare’s Richard III and Victor Hugo’s Quasimodo, The Hunchback of Notre Dame. Our modern society often appears obsessed with physical beauty and it seems as if these societal pressures are greater on women and girls. It is important, then, to be mindful of the potential impact that spinal deformity may play on the patient’s body image and emotional health. Studies of patients with idiopathic scoliosis bear out this concern, with findings showing poorer body image, greater unhappiness, lower self-esteem, increased participation in high-risk behaviors, and greater incidence of depression (42, 43, 44). Questions relating to the emotional and behavioral status of a patient with spinal deformity should be a regular part of the physiatrist’s ongoing follow-up of the patient. There should be no hesitation to enlist the help of psychological support professionals such as rehabilitation psychologists and social workers to address the emotional needs of the patients and their families.

A number of disorders of vertebral development can occur. These anomalies are present at birth, but they may not be detected immediately. The curvature may be subtle and not noticed until the child begins sitting or standing. Often, clinical evidence of curvature may not be apparent until the child grows and one part of the vertebral column grows faster than another, thus revealing the asymmetry associated with the anomaly. Winter (45) has developed a classification system for these anomalies based on the underlying embryological dysfunction. The dysfunction may be a failure of segmentation, a failure of formation, or a combination of both. The archetype of segmentation failure is a bloc vertebra, formed at two or more spinal levels. This is less likely to cause a curve than a unilateral failure to segment, known as a unilateral bar. The location of the bar will determine the type of pathological curve. A lateral bar will result in scoliosis, a posterior bar will produce kyphosis, and an anterior bar will result in lordosis.

The defect in formation that will result in curvature is usually called a hemivertebra. In reality, any amount of partial defect is possible. The partial vertebra may be “incarcerated,” meaning that the vertebrae above and below it have altered their shape to compensate for the abnormal shape of the partial vertebra, therefore limiting the degree of curvature. A nonincarcerated hemivertebra is more likely to result in curvature because its neighboring vertebrae have not adapted to the hemivertebra’s abnormal shape. Figure 34-10 shows representations of the basic types of deformities according to the Winter classification.

Although congenital bony anomalies may be isolated, it is incumbent to first rule out associated genetic disorders. From 25% to 40% of children with congenital bony anomalies also have other problems including genitourinary anomalies, cardiac anomalies, Klippel-Feil syndrome, and spondylothoracic dysplasia. However, the majority of curves due to congenital bony anomalies are not severe. Only 38% show severe progression, whereas 47% show only mild to moderate
progression and 15% show no progression (46). The character of the curve will help determine likelihood of success of a given treatment approach. Long, flexible curves may respond to orthotic management. Short, stiff curves will require surgery if they progress.