The nominal spine functions as a support structure providing protection of the neutral elements and movement of the various motion segments. Anatomy of the spine is such that the thoracic spine has a natural round or kyphotic appearance, the cervical and lumbar segments being oriented to produce a lordosis. The arrangement of the posterior facet articulation is such that movement is possible yet stability is maintained.

Individuals vary as to the degree of sagittal curvature. Thoracic kyphosis normally ranges from 20 to 45⁰ and lordosis averages 50⁰ in the lumbar spine. The normal spine alignment shows no lateral deviation, yet up to 10 per cent of the population may have minor lateral deviation or scoliosis. Small deviations of the norm do not seem to cause symptoms, but greater curvature may produce pain, and muscle fatigue; as deformity increases in its severity, neural elements and viscera may be affected.

Treatment of spinal deformity is dependent upon the type and degree of deformity in addition to the aetiology and age of the patient. During growth, treatment may take advantage of residual growth in attempting to correct or hold the deformity from becoming severe. After skeletal maturity, correction of the deformity becomes more difficult.

Spondylolisthesis is a term used to describe the forward slippage of one vertebral body upon another. There are several distinct conditions that may give rise to this problem and the classification of spondylolisthesis is based upon conditions that may bring about the deformity. This classification has developed from the work of Neuman, McNabb, and Wiltse.

1.Congenital—slippage generally of L5 and S1 as a result of congenital anomalies at the lumbosacral junction.

2.Isthmic—a result of a defect in the pars interarticularis due either to a fracture or elongation of this structure.

3.Degenerative—forward slippage due to degenerative changes within the disc and subluxation at the posterior facet articulation.

4.Traumatic—deformity due to acute fracture in areas other than the pars interarticularis.

5.Pathological—spondylolisthesis as a result of generalized destruction of bone due to a neoplastic lesion especially involving the posterior column.

6.Postsurgical or iatrogenic—instability as a result of partial or complete loss of the posterior element and of the discogenic support of the motion segment as a result of surgery.

This condition is due to a congenital anomaly involving the L5 and S1 articulation. This type of spondylolisthesis has been divided into two subtypes depending upon whether or not there is spina bifida. Slippage in the congenital type may often occur earlier than in other forms. Patients may often have leg pain and back spasm; pain and altered gait due to hamstring spasm brings the patient to the physician. Not only does the slippage develop early, but it may also be quite rapid in its progression. Subtype A has a defect not only at the articulation but also in the posterior ring and as such a spina bifida exists. In subtype B the posterior ring remains intact and there may be neurological deficit due to compression of the L5 nerve root. Treatment of the asymptomatic patient involves observation unless severe slippage is present in which case a posterior lateral fusion is recommended. In the symptomatic patient, stabilization with posterior lateral fusion is recommended; if the neurological picture does not improve, a secondary decompression may be carried out following stabilization with fusion.

Forward slippage of the vertebrae in the lumbar spine may be a result of abnormality of that portion of the posterior elements referred to as the pars interarticularis. The pars interarticularis may actually have a bony defect present or may be elongated. The aetiology of this type of spondylolisthesis has remained controversial. Many authors support the notion of a developmental defect within the pars not present at birth. In other individuals, an acute or stress fracture occurs across the pars. Current thinking suggests that developmental factors exist and are possibly related to a congenital type of spondylolisthesis that in certain individuals predisposes to the development of stress fracture. Children and adolescents involved in sports such as gymnastics and football are much more likely to develop this type of spondylolisthesis. This is felt to be due in large part to hyperextension stress placed across the pars interarticularis. In certain individuals a defect in the pars may be present without any suggestion of slippage or spondylolisthesis, referred to as spondylolysis.

The majority of individuals with spondylolysis and spondylolisthesis are asymptomatic. When symptoms do develop, there are complaints of pain, which may be in the back, seemingly related to activity and to nerve root irritation. Pain may not always be related to the magnitude of the slip. The aetiology of pain in spondylolisthesis is not clear. Physical findings may show an individual with an obvious deformity in the lower spine; gait may be abnormal usually due to hamstring tightness. Neurological abnormalities are present in 18 to 50 per cent of symptomatic cases. Radiographic studies should include standing, anteroposterior, lateral, and oblique films, CT scan, tomography, and myelography. A bone scan may also be of value in determining acuteness of the stress fracture.

Radiographs have been helpful in determining progression of the deformity and prognosis. The percentage of slippage based upon the area of sacrum uncovered by the forward slip of L5 is divided into five grades. Grade 1 is 0 to 25 per cent, grade 2—25 to 50 per cent, grade 3—50 to 75 per cent, grade 4—75 to 100 per cent, and grade 5 is complete forward slippage of one vertebrae upon the other. The slip angle has also been used in an attempt to determine prognosis.

The earlier the patient becomes symptomatic, the greater the risk of progression. Women also have a greater risk of progression. On radiography, a dome-shaped sacrum and a trapezoid appearance of the L5 vertebrae seem to have a greater chance of progression as does a slippage of 50 per cent or greater and a significant slip angle. In the asymptomatic individual, observation to maturity is recommended. If the slip is greater than 50 per cent, fusion should be seriously considered, especially if several risk factors are present. In the symptomatic patient, non-operative treatment involves rest and curtailing activity with progressive strengthening exercise. A brace may be used if there is no improvement with the treatment mentioned above and if a stress fracture is identified with a positive bone scan. After acute stress fractures there is a 78 per cent success rate of resolution of symptoms with bracing.

Surgical treatment is reserved for patients who fail conservative measures, have disabling back pain, have slips greater than 50 per cent, and have multiple risk factors. The most commonly used procedure is bilateral posterolateral fusion in situ. Typically the fusion extends from L5 to S1 unless the slip is greater than 50 per cent, when L5 should be fused also.

Decompression of the cauda equina is indicated when there is neurological deficit. However, neurological symptoms have been shown to resolve with fusion alone. Indications for instrumentation and reduction of the slip at the present time is not well established but it has been noted that in spondylolisthesis of grade III and IV fusion as such without reduction has a higher rate of pseudoarthrosis and possible progression of slip. Several methods have been attempted to bring about reduction and decrease the deformity and thereby improve the fusion rate. Both open and closed, anterior and posterior, and combined procedures have been recommended. Open reduction techniques, however, have a high incidence of complications including instrument failure and neurological compromise and as such, fusion in situ is still the most accepted procedure followed by immobilization in spica cast.

Not all patients with spondylolysis or spondylolisthesis are symptomatic. In virtually all untreated patients back pain was present in adulthood; in half of these cases, sciatica was the presenting complaint, with 18 per cent of the individuals having a neurological deficit. Generally patients with spondylolysis and spondylolisthesis who present themselves as adults may be treated with conservative methods. These include a well structured back strengthening programme, intermittent use of a corset, and occasional use of anti-inflammatory medication. Treatment is similar to those patients who present with mechanical back pain. Indications for surgery are disabling back pain and pain unrelieved by conservative measures. Preoperative MRI and myelogram is indicated to rule out other causes of pain.

Adult patients may often have a higher incidence of radiculopathy than adolescents; recommendations in such cases include decompression with removal of posterior elements and of the fibrocartilaginous mass that is present within the defect, followed by a posterolateral fusion. Instrumentation with or without reduction has been advocated with the hope of decreasing pseudoarthrosis rate especially in individuals who have a greater than grade 2 slippage.

In the presence of long-standing intersegmental instability a vertebra may begin to slip. This type of spondylolisthesis occurs six times more frequently in females than in males and is six to nine times more frequent at the L4 - 5 interspace than at the adjoining level. It is felt that the L5 vertebrae is more stable especially when it is located below the intercristal line which is the cephalic border of the iliac crest. Degenerative spondylolisthesis usually does not slip further than one-third the width of the vertebral body and it is rarely seen under the age of 40.

Non-operative treatment includes instruction and initiation of a back exercise programme stressing both extension and flexion exercises in an attempt to strengthen the abdominal and paraspinal muscles. Use of anti-inflammatory medication is often helpful. Patients who develop increasing pain with exercise benefit from facet injection of local anaesthetic and steroids. In the patient who has acute sciatic irritation, epidural steroid may bring about relief and resolution of the acute situation.

If the patient does not respond to conservative measures and has disabling back and leg symptoms, surgery should be considered. The procedure is directed at the production of stability through fusion of the unstable level and decompression of the neural elements if radicular symptoms persist.

Treatment of patients with degenerative spondylolisthesis and radiculopathy is controversial. Most surgeons favor decompression and arthrodesis of the involved segment with posterior lateral fusion. Fusion is generally recommended because of reported incidence of progressive slippage in 15 to 42 per cent of patients. However, this is not universally accepted. In a recent study the treatment of degenerative spondylolisthesis with decompression alone gave satisfactory results. We feel that decompression alone is satisfactory. Patients who have spondylolisthesis without considerable degenerative change, especially with signs of instability on flexion extension views should undergo an arthrodesis.

Scoliosis refers to a lateral deviation of the spine, but is also a rotational deformity, often associated with abnormalities in the sagittal plane. New investigations and radiographic techniques have shown that scoliosis involves deformity in three planes. Present-day treatment techniques attempt to address all three planes of deformity.

Recent studies have documented a subtle abnormality in balance and proprioception in patients with idiopathic scoliosis. In some, this appears to be a disturbance in the function of the posterior column of the spinal cord while in others, the abnormality appears to be in the vestibular system. Idiopathic scoliosis is divided into four different categories that are defined by age and account for 85 per cent of all scoliosis cases.

This type of scoliosis is seen in children of less than 3 years of age and there appears to be an equal incidence in male and female populations. The incidence in Europe and Great Britain appears to be much greater than in the United States. Two types of infantile scoliosis exist: resolving and progressive. Mehta in 1972 determined a method for identifying progressive infantile scoliosis. This method involves measuring the angle between the rib and vertebral body on the concave and convex surface of the curve. In 80 per cent of cases with progressive curve, the rib vertebral angle difference is greater than 20⁰. Progressive infantile scoliosis can be very difficult to treat. While attempts should be made to control the curve with bracing, it is often necessary to be more aggressive.

Idiopathic scoliosis diagnosed between the age of 4 and adolescence is classified as juvenile. It appears more commonly in females than males, but there is no definite way to determine which curves are progressive. The treatment of the juvenile with idiopathic scoliosis depends upon the degree of presenting curve. If curves are less than 20⁰, observation is indicated at 6-month intervals with special attention being indicated as the child progresses through growth spurts. In curves of 25 to 30⁰ or if progression of 5⁰ or more is noted between consecutive visits, brace treatment is indicated. In spite of bracing, some idiopathic scoliosis progresses.

This is the largest group of patients with idiopathic scoliosis. While the idiopathic curve may begin during the juvenile years, it only becomes apparent during adolescence. Not all of these curves are significant, nor do all progress. The difficult problem for the treating physician is in trying to determine which curves will progress and require treatment. Several studies have investigated the prevalence rate of idiopathic scoliosis, placing the rate at 2 to 4 per cent of the population for curves of 10⁰ or more. Only three patients per thousand will develop a progressive curve beyond 20⁰ and require definitive treatment.

Although the progression of curves cannot be predicted, certain criteria have been developed to determine the probability. These criteria include the curve pattern (double curves seem to have a greater risk of progression while lumbar curves seem to have the least risk). With increasing age, there appears to be a decreasing risk of progression. Menarche seems to play a role. Curves before menarche have a much greater chance of progression than those detected after. The larger the curve at initial diagnosis, the greater the chance of progression.

The incidence of scoliosis appears to be equal in the male and female population but the risk of progression is ten times greater among women compared with men with a comparable curve. The radiographic Risser sign relates to the growth of the iliac apophysis and is used as a predictor of remaining skeletal growth. In curves of less than 20⁰, the rate of progression is 22 per cent if the Risser sign is 0 to 1, but reduces to 1.6 per cent in patients that present with a Risser sign of 2 to 4. In curves of greater than 20⁰ a patient with 0 to 1 Risser sign has three times the chance of progression compared with a patient who is reaching skeletal maturity.

The majority of patients with adolescent idiopathic scoliosis will need observation only. Generally, follow-up is recommended at 6-month intervals. Even the most progressive curves will generally not progress more than 1⁰ per month so that there is little point in obtaining follow-up studies more often than every 6 months.

The role of bracing is to stop the progression of curve in an attempt to keep the curve below 40⁰ (this seems to be a cut-off with regard to the effectiveness of the bracing treatment). Braces attempt to bring about correction through lateral force and derotation of the spine. There is no difference in the effectiveness of the various braces.

Curves of 20⁰ or less should be observed, since the majority will not require brace treatment. Bracing should be reserved for the immature patient with curves of 25⁰ or more and who have shown at least 5⁰ of progression. For curves of greater than 30⁰ on the initial progression in a skeletally immature individual, bracing is indicated. Initially, brace treatment was instituted for 23 h a day; however, compliance was generally not good and attempts at part-time bracing have been advocated. Several studies confirm that brace treatment can be effectively carried out if the brace is worn 16 h a day. Bracing is ineffective if the curve is beyond 40 to 45⁰.

Although the majority of patients with idiopathic adolescent scoliosis may be treated with observation or bracing, surgery is still indicated in certain individuals. Those that present with curves of greater than 50⁰ and are still skeletally immature often progress to severe curvature despite brace treatment. First attempts at surgery for scoliosis involved in-situ fusion. This was followed by attempts at serial casting and fusion. The great breakthrough in the treatment of scoliosis came in the late 1950s with the development of spinal instrumentation by Harrington. He implanted a distraction rod combined with posterior intra-articular fusion which for 30 years has been the gold standard for treatment of adolescent idiopathic scoliosis. While newer methods of instrumentation have evolved, they must be compared to the excellent success of this system. The incidence of complications, that is, of neurological problems, was less than 1 per cent, pseudoarthrosis rate was less than 5 per cent, and curves could be corrected on the average of 40 per cent.

During the late 1970s and throughout the 1980s, several posterior instrumentation systems have been developed. All attempt to provide increased correction of the spinal deformity and to provide more rigid immobilization. The Luque system involved the use of sublaminar wire and provided excellent fixation and curve correction. With the passage of sublaminar wires, however, the incidence of neurological injury increased. Drummond modified this system by providing segmental fixation with a series of wires through the spinous process rather than sublaminarly. Wires are attached to a distraction rod on the concavity of the curve and a Luque rod applied to the convexity. Both rods are secured by the Drummond wires.

Adults with scoliosis may present with complaints of compromised pulmonary function, neurological deficit due to nerve root compression, or dissatisfaction with their altered body image. Patients with scoliosis have an incidence of low back pain similar to that of the general population; however, as the degree of curvature increases, severity of pain becomes much more of a problem. Patients with scoliosis who undergo surgical treatment experience a significant decrease in pain that is not always possible with conservative measures.

The patient who presents with pain and scoliosis may be a candidate for non-surgical treatment especially if the pain seems to be mechanical. Treatment methods are similar to those used in treating mechanical pain for the general population, and involves the use of analgesics, anti-inflammatory medication, and exercise. In a large number of patients, especially in those without severe scoliosis, treatment will be successful. Exercise are designed to provide dynamic stability to the segments involved. Intermittent use of a flexible lumbar support may also be beneficial.

Indications for surgery in adult patients are not often as clear cut as in the adolescent. Much attention must be given to the patient's symptoms as well as their expectations. The adult patient must be made well aware of the morbidity and even mortality rates for adult scoliosis. These are significantly higher than in adolescents. Complications rates have been reported as high as 30 to 50 per cent, including a 15 per cent pseudoarthrosis rate and a rate of incidence of instrument failure up to 12 per cent.

The main goals of surgical treatment are the relief of pain and curve stabilization. This is different from the situation in the adolescent, where considerable correction of the curve can be achieved. Surgery is usually recommended in adult patients who have a thoracic curve of 60⁰ or greater, and patients with a single lumbar or thoracolumbar curve of 50⁰ or greater. Patients with double curves in the 55 to 60⁰ range are generally also candidates for surgical correction and fusion. Curves of lesser magnitude in patients who are symptom free and without progression generally are kept under observation.

Scoliosis surgery in adults is technically more difficult than in adolescents. Curves are more rigid and correction is correspondingly more difficult to bring about. In addition, with ageing, bone quality may deteriorate posing problems for fixation of hardware. Surgical instrumentation principles in adult scoliosis surgery are the same as in the adolescent.

Spinal deformity may develop either by a failure of formation or by a failure of segmentation. The hemivertebrae, an example of failure of formation, may produce a progressive scoliosis above and below the involved segment. The unilateral unsegmented bar, a result of failure of segmentation, is the most frequent cause of congenital scoliosis. This produces a malignantly progressive deformity that can be treated only with surgical stabilization. As with idiopathic scoliosis, the location of the deformity has some effect on the prognosis. Deformities located in the lower thoracic and thoracolumbar spine are most likely to progress and deformities in this area often produce development of secondary lumbar or thoracolumbar curves that may become structural. Curves located in the upper thoracic region appear to have the best prognosis.

Spinal deformities resulting from congenital anomaly generally carry a poor prognosis, especially if the deformity is due to a unilateral unsegmented bar. Once this underlying deformity is noted, fusion should be performed in order to prevent progression. In the case of a hemivertebrae, the prognosis is not as bleak and often these curves will not progress to a severe deformity. As such, observation is indicated. In the case of the hemivertebrae, however, if progressive deformity is noted, posterior fusion should be recommended and in certain selected cases, anterior interbody fusion may be recommended on the convex side of the curve to arrest the growth on the convex side. This policy allows for some progressive correction of the deformity with continued growth on the concave side of the curve. There is only limited indication for use of brace treatment in congenital scoliosis.

Progression of congenital scoliosis often occurs quite young and previously there has been much concern regarding operative fusion in these patients, the fear being that early fusion would arrest growth. While there is no question that fusion will stop growth of the vertebral body, it will prevent progression of the deformity and overall longitudinal growth will not be as affected as it would be if the deformity is allowed to progress.

Neuromuscular scoliosis is that spinal deformity brought about by muscle imbalance of either a spastic or flaccid type. It includes patients with cerebral palsy, myelodysplasia, or various forms of muscular atrophy and dystrophy. Progression is very common and the patient's neuromuscular abnormalities may begin very early, depending upon the aetiology. This type of scoliosis can lead to severe deformity and interfere with daily activities, even with sitting balance. The patients who are more seriously affected neurologically generally have a more severe progressive scoliosis. The treatment of the patient with neuromuscular scoliosis depends upon the degree of curve and the functional status of the patient. Scoliosis is common in patient with cerebral palsy; the prevalence rate is as high as 64 per cent. Scoliosis is most common in patients with spastic quadriplegia.

The treatment of a moderate curve, greater than 25 to 30⁰ with progression, can be carried out using a removable plastic jacket. However, even with such treatment, the curve may continue to progress.

Surgery is indicated in the treatment of progressive neuromuscular scoliosis when the curve cannot be controlled within an orthosis and especially when sitting balance is disrupted. Surgical treatment carries a fairly high complication rate. Pseudoarthrosis prior to the use of segmental stabilization was quite common. Beginning with the Luque system, and currently with the newer methods of segmental stabilization, curve correction and stabilization is possible, often without the need for postoperative immobilization. Patients often have a pelvic obliquity requiring instrumentation to the pelvis.

Duchenne's muscular dystrophy is the most common type. It is a relentlessly progressive neuromuscular disorder. Early in life, these patients are often minimally affected, but by the age of 12, many have become confined to a wheelchair. Once wheelchair-bound, they begin to develop severe collapsing spine deformity. The scoliosis often limits their ability to sit and compromises their pulmonary function. Bracing is poorly tolerated, as it interferes with an already limited lifestyle. Because of the progressive nature of the curve and interference with pulmonary function, surgery is recommended early in patients with Duchenne muscular dystrophy. It has been recommended with curves as small as 25⁰ if pulmonary function is still adequate for surgery. These patients have a long gentle curve involving the pelvis and the entire spine must be fused including stabilization to the pelvis using the Galveston technique.

Patients with myelodysplasia have the worst combination of neurological and congenital deformity and this may lead to some of the most difficult deformities to treat. If the major deformity is that of a congenital anomaly, as in spina bifida, treatment is similar to that recommended for congenital scoliosis. Thus, once progressive curve is noted, localized fusion is recommended. The cause of progression in the patients with myelodysplasia may be due to an intraspinal lesion such as diastematomyelia or tethering of the spinal cord. These will often cause changes of progression of the neurological deficit in the lower extremities. Correction of spinal deformity with instrumentation without releasing the point of tethering will often have a deleterious effect on the remaining neurological function. As in patients with other types of neuromuscular scoliosis, the use of segmental instrumentation has proven beneficial, including incorporation of instrumentation into the pelvis. Many patients with spina bifida have marked deficit in their posterior elements and fixation to the spine through the use of pedicle screws has been seen to work quite well. At times, combined anterior and posterior instrumentation and fusion may be necessary.

This deformity of the spine occurring in the sagittal plane is also known as round back. It will often go untreated, as a certain amount of kyphosis in the thoracic spine is normal. Studies have been undertaken to define what is a normal degree of thoracic kyphosis. There appears to be great variability but on average, the range is from 25 to 40⁰; anything above 50⁰ is viewed as abnormal. Scheuermann's disease is the most common cause of kyphotic deformity and this is secondary to vertebral wedging. Other causes of kyphosis may be congenital with failure of formation or failure of segmentation of the thoracic vertebrae. Kyphotic deformities may result from vertebral destruction in infections such as tuberculosis or metastatic disease. Certain people have an increased kyphosis without any underlying structural abnormalities of the spine, and are classified as having a postural kyphosis.

Congenital kyphosis, due to failure of normal vertebral development, tends to be a progressive lesion. Severe deformity, especially in areas of failure segmentation, develops early with the possibility of neurological compromise. The treatment of congenital kyphosis is surgical, as bracing has not been found to be helpful. Early surgical intervention with posterior fusion often prevents the progression of the deformity but if the patient is more than 5 years of age and with deformity of greater than 50⁰, generally an anterior release followed by a posterior stabilization is necessary to stabilize the deformity.

Scheuermann's disease, also known as juvenile kyphosis, comes about as a result of wedging of the vertebral bodies. This may occur within the thoracic spine but also is present at the thoracolumbar junction and the lumbar spine. Diagnosis is made based upon radiographic findings and the criteria for classic Scheuermann's disease include: (1) irregular vertebral end plate, (2) apparent narrowing of the intravertebral disc space, (3) three adjacent vertebrae wedged 5⁰ or more, and (4) an increase in the normal thoracic kyphosis above 45⁰. The aetiology of this deformity is unclear.

Treatment of juvenile kyphosis or Scheuermann's disease is directed at correcting the deformity. This is somewhat different to the initial treatment of scoliosis, in which attempts to arrest the progress of the presenting curve are made. Indicators for the Milwaukee brace in the treatment of Scheuermann's disease include a kyphotic curve of 55⁰ or greater in the immature individual. The brace appears to function by unloading the anterior portion of the vertebral body, thereby allowing growth to proceed in the skeletally immature individual. Correction of the deformity with conscientious brace wearing may actually be seen. Total bracing generally averages 2 to 3 years with at least 1 year full-time brace wear. Long-term follow-up has shown that with conscientious wear, more than 60 per cent of the patients will improve, approximately 10 per cent will remain unchanged, and between 20 and 30 per cent undergo progression.

If the patient has deformity of 70⁰ or greater, especially in someone approaching skeletal maturity, it is best to consider surgical correction. In the young skeletally immature individual who shows good correction on hyperextension of the deformity over a bolster, even a deformity of 70⁰ may be treated with bracing. Surgical treatment most often proceeds with release of the anterior longitudinal ligament, anterior removal of disc material, and an interbody fusion of the vertebral bodies involved in the apex of the deformity, generally five to seven vertebral bodies. This is followed by a posterior instrumentation and fusion. In individuals with an exceptionally flexible spine, in which hyperextension films are able to reduce the deformity to a physiological range (i.e. 45 to 50⁰), posterior instrumentation and fusion may be considered. The incidence of pseudoarthrosis with posterior fusion alone, however, is greater than for an anterior and posterior procedure. In young, healthy patients, the anterior and posterior procedure may be carried out in the same surgical setting. Instrumentation involves the use of heavy Harrington compression rods. Spinal stabilization and correction using Luque rods and sublaminar wire has also been advocated. At present C-D or TSRH instrumentation appears to be the implants of choice. As with all procedures designed for correction of deformity, the most important aspect of the procedure is to bring about solid arthrodesis.

Ascani E, et al. Natural history of untreated idiopathic scoliosis after skeletal maturity. Spine 1986; 11: 784 - 9.

Boachie-Adjei O, et al. Management of neuromuscular spinal deformities with Luque segmental instrumentation. J Bone Joint Surg 1989; 71A: 548 - 62.

Bradford DS. Spondylosis and spondylolisthesis. In: Bradford DS, Lonstein JE, Moe JH, et al., eds. Moe's textbook of scoliosis and other spinal deformities. 2nd edn. Philadelphia: WB Saunders, 1987.

Cambridge W, Drennan JC. Scoliosis associated with Duchenne muscular dystrophy. J Pediatr Orthop. 1987; 7: 436 - 40.

Deacon P, Archer IA, Dickson RA. The anatomy of spinal deformity: a biomechanical analysis. Orthopaedics 1987; 10: 897 - 903.

Emnas JB, et al. The Boston bracing system for idiopathic scoliosis: follow-up results in 295 patients. Spine 1986; 11: 792 - 801.

Freeman BL III, Donati NL. Spinal arthrodesis for severe spondylolisthesis in children and adolescents: a long term follow up study. J Bone Joint Surg 1989; 71A: 594 - 8.

Grubb SA, Lipscomb HJ, Coonrad RW. Degenerative adult onset scoliosis. Spine 1988; 13: 241 - 5.

Hanks GA, Zimmer B, Nogy J. TLSO treatment of idiopathic scoliosis: an analysis of the Wilmington jack. Spine 1988; 13: 626.

Luk KDH, et al. The comparative results of treatment in idiopathic thoracolumbar scoliosis using Harrington. Dwyer, and Zielke instrumentation. Spine 1989; 14: 275 - 80.

Pin LH, et al. Early diagnosis of scoliosis based on school screening. J Bone Joint Surg 1985; 67A: 1202 - 5.

Pizzutillo PD, Mirenda W, MacEwewn GD. Posterolateral fusion for spondylolisthesis in adolescence. J. Pediatr Orthop 1986; 6: 311 - 16.

Symposium. Management of adult scoliosis. Lonstein JE, Moderator. Contemporary Orthopaedics 1986; 12: 71 - 100.

Thometz JG, Simon SR. Progression of scoliosis after skeletal maturity in institutionalized adults who have cerebral palsy. J Bone Joint Surg 1988; 70A: 1290 - 6.

Weinstein SL. Idiopathic scoliosis: natural history. Spine 1986; 11: 780 - 3.

Winter RB, et al. The effectiveness of bracing in the nonoperative treatment of idiopathic scoliosis. Spine 1986; 11: 790 - 1.

Winter RB, Moe J, Eilers V. Congenital scoliosis: a study of 234 patients treated and untreated. J Bone Joint Surg 1968; 50A: 1 - 47.