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This article outlines the epidemiology, pathogenesis, clinical manifestations, imaging and pathology features, current treatment, and prognosis of this disease.

Epidemiology

Scheuermann’s disease is most frequently diagnosed between ages 13 and 17 years. The overall incidence is 0.4% to 10%. The typical patient is between the late juvenile to age 16 years, commonly between 12 and 15 years. There is no specific gender prevalence.

There are two major forms of Scheuermann’s kyphosis: the thoracic form (classic, type I), which is the most common with the apex localized between T7 and T9 vertebrae and the thoracolumbar form (type II), with the apex localized between T10 and T12. A third lumbar form of the disease that occurs mostly in active male patients has been reported.

Pathogenesis

The etiology of Scheuermann’s kyphosis remains unclear. Scheuermann first explained it as a result of aseptic necrosis of the ring vertebral apophyses. Histologic studies have revealed abnormal vertebral endplate cartilage, irregular mineralization, disorders in vertebral ossification, and alterations in collagen aggregation with abnormal collagen-proteoglycan ratios. Other studies have reported the causative association of Scheuermann’s kyphosis with dural cysts, Legg-Calvé-Perthes and Beckhterew’s diseases, infections, spinal dysraphism, and other pathologic conditions such as hypotonia or hypertonia, poliomyelitis, rickets, endocrine disorders, and constitutional kyphosis.

Scheuermann’s disease is considered hereditary, although the hereditary pattern has not been clearly defined. The mode of inheritance may be autosomal dominant, with a high degree of penetrance and variable expressivity. Reports suggest heritability of identical radiological changes in monozygotic twins, sib recurrence, and transmission through generations. Genetic factors in the etiology of the disorder have yet to be defined.

Previous reports have noted decreased bone mineral density in patients with Scheuermann’s kyphosis, however, recent studies have not shown any statistical significant differences of the trabecular bone density and alkaline phosphatase levels between groups of patients and controls.

Growth hormone hypersecretion also has been related to the pathogenesis of Scheuermann’s kyphosis. Patients with the disease were found to be taller than the percentile mean height for their age. However, no studies exist to define causative relation between growth hormone secretion and Scheuermann’s disease and its role remains unclear.

Biomechanical factors may have a significant role in the etiology of Scheuermann’s kyphosis. The radiological changes of the disease may be expressions of altered remodeling response to abnormal biomechanical stresses, and that the anterior vertebral body wedging is secondary to the increased anterior forces due to the first occurring kyphosis. In the classic, type I form of the disease, bilateral hamstring tension is a common finding, which according to another theory is thought to be the cause of focusing bending stresses on the thoracic spine. Neuromuscular disorders may be additive but not causative factors in the development and progression of the deformity.

Signs and Symptoms

The onset of the disease usually is around age 10 years. In many young patients the disease is misdiagnosed as postural kyphosis, or neglected due to lack of the disease-specific radiographic findings and absence of the ring apophyses ossification centers.

In the majority of the patients, thoracic kyphosis usually is painless and flexible. When symptomatic, pain may be aggravated by physical exertion; however, persistent pain may have other causes. Back pain is more common in high competitive athletes, and in athletes with high demands on their back, such as wrestlers and gymnasts. Deformity and cosmetic appearance are also common in all patients, especially the young and the adolescents.

An interesting clinical sign is a cutaneous skin pigmentation that appears at the most protruding spinous process at the apex of the kyphosis, due to skin friction at the back of the chair. Forward protruded position of the head, round anteriorly positioned shoulders and occasionally anterior flexion contractures of the shoulder joint, flexion contractures of the hip joint, and tight hamstrings, are common findings and may be early and salient symptoms in the onset of the disease.

Kyphotic deformity in Scheuermann’s disease usually is associated with a moderate, compensatory lumbar and cervical lordosis. Lumbar spine hyperlordosis has been observed in >50% of the patients and was thought to result in increased stresses on the pars interarticularis that may account for the increased incidence of spondylolysis reported in patients with Scheuermann’s disease. Scheuermann’s kyphosis is also often associated with a moderate scoliosis, which is modest, and with a later onset than in true idiopathic scoliosis.

In the thoracolumbar form of Scheuermann’s kyphosis, the lower located curve apex may paradoxically reduce the normal thoracic kyphosis and clinically mimic a thoracic lordosis. Patients with this form of the disease usually report greater pain and localized vertebral tenderness and greater restriction in physical exercise, work, and activities of daily living. Most of the patients with the lumbar form of the disease present with persistent low back pain. This variant is more likely to be progressive in adulthood and more often symptomatic.

Neurologic deficits are rare, including gradual and progressive lower extremity weakness with back and radicular pain, and spastic paraparesis. Neurologic deficits are usually secondary to thoracic disk herniation, kyphotic angulation and tenting of the spinal cord, extradural spinal cysts, osteoporotic compression fractures and vascular injury to the anterior spinal artery due to compression of the spinal artery of Adamkiewicz.

The consequences of kyphotic deformity on pulmonary function are unclear. In a study, surgical treatment did not adversely affect patients whose pulmonary function was normal preoperatively and no correlation was found with cardiopulmonary insufficiency, except for the most severe curves, of >110°.

Differential Diagnosis

Scheuermann’s disease is characterized by a rigid or relative rigid thoracic, thoracolumbar, or lumbar kyphotic deformity with certain radiographic findings. It is important to differentiate Scheuermann’s from postural kyphosis. The latter is a benign condition secondary to the patient’s bad posture. The thoracic postural kyphosis is gently rounded, clinically flexible and Scheuermann’s specific imaging findings are not observed. The patient’s body type in Scheuermann’s disease often is more athletic, in contrast to the asthenic type of patients with nonstructural kyphosis. In the forward-bending test, the patient with postural kyphosis shows a smooth, flexible, and symmetric contour, while patients with Scheuermann’s disease demonstrate an area of angulation in a fixed or relatively fixed kyphotic curve. Other pathologic entities that must be differentiated include idiopathic kyphosis, specific or not spondylitis, osteochondral dystrophies and spondyloepiphyseal dysplasias, and congenital kyphosis.

Imaging Features

Initial imaging study includes standing posteroanterior and lateral radiographs of the entire spine. The normal thoracic kyphosis in the growing adolescent, defined by the Scoliosis Research Society, ranges from 20° to 40°.

The typical radiographic findings of the disease, first described by Scheuermann, were the upper and lower vertebral endplates irregularity, and vertebral body wedging of at least 5°; however, measurement of the vertebral wedging can be difficult, particularly in skeletally immature patients.

Schmorl’s nodes are the result of the penetration of nucleus pulposus material into the spongy vertebral body.2 This finding is frequent but not pathognomonic of the disease, since it can also be observed in normal individuals. Additional imaging findings include disk space narrowing or loss of disk space height, especially in advanced stages of the disease, increased anteroposterior diameter of the apical thoracic vertebrae, loss of the normal height of the involved vertebra, and kyphotic deformity.

Associated conditions such as scoliosis, lordosis, and spondylolysis may occur.

The degree of kyphosis on the lateral radiographs can be measured using the Cobb method. The measurement of the vertebral wedging can be difficult, especially in skeletally immature patients without radiographic appearance of vertebral ring apophyses. In this case, the lateral profile of the vertebra has a curvilinear rather rectilinear shape. In the lumbar form of Scheuermann’s kyphosis, the kyphotic deformity is located at the thoracolumbar junction and it is usually not of clinical significance. The Schmorl’s nodes and endplates irregularities may be severe, and mimic other, infectious or malignant pathologic conditions. Typical of lumbar Scheuermann’s kyphosis is the marginal anterior detachment of the vertebral body.

Clearly, not all of the typical radiographic findings are required for the diagnosis of Scheuermann’s disease. Some investigators consider as Scheuermann’s kyphosis any thoracic kyphosis of >45° associated with >1 vertebra wedged at least 5°, while according to others the diagnosis depends on the rigidity of the kyphotic curve as this is evaluated on lateral hyperextension plain radiographs of the spine. According to Sorenson, criterion for the radiographic diagnosis of Scheuermann’s disease is a minimum of three contiguous apical vertebrae wedged by at least 5° each, whereas Drummond’s criterion is 2 wedged vertebrae. Bradford’s criterion is that >1 vertebrae are wedged >5°. This criterion leads to earlier diagnosis.

Additional imaging studies should include passive hyperextension views, lateral tomograms, radiographs of the left hand and wrist, and standing posteroanterior radiograph of the pelvis.

Bone scintigraphy and magnetic resonance imaging (MRI) are generally not necessary for the diagnosis of Scheuermann’s kyphosis. Bone scintigraphy findings are generally not pathognomonic, appearing as subtle increases in isotope uptake at the sites involved by the disease. Magnetic resonance imaging is used in the evaluation of neurologic deficits and intervertebral disk degeneration and atypical forms of Scheuermann’s disease with nondiagnostic findings in standard radiographs. A CT-myelogram might also be proved useful in cases of documented neurologic deficits such as spinal cord compression, especially at the thoracic region with spinal stenosis and paraparesis. Preoperative selective arteriography of the spine may be of value to avoid injury of the anterior spinal artery.

Treatment

In defining the best treatment for the patient, the doctor should be aware of the natural history of the disease, determine specific criteria for initiating therapy and weight the benefits against the complications. Many investigators in the past have reported specific criteria for the treatment of Scheuermann’s kyphosis. These criteria include pain that does not respond to any nonoperative treatment, progressive thoracic deformity, neurologic deficits, cardiopulmonary compromise, cosmetic deformity and psychological problems of the patient because of the deformity. Unlike idiopathic scoliosis, no data exists regarding the progression of the kyphotic deformity in Scheuermann’s disease.

Soo et al suggested careful selection of the appropriate treatment for patients with Scheuermann kyphosis on the basis of patient’s age, spinal deformity, and severity of back pain. Generally, skeletally immature patients with a kyphotic curve of 45° to >50°, and radiographic findings of Scheuermann’s disease may be candidates for initiating treatment with physical therapy and bracing. Intensive physiotherapy exercise programs for postural improvement have been tried for many years but without any conclusive data that physical therapy alone can benefit kyphotic improvement. Extension sports such as gymnastics, aerobic, swimming and basketball, cycling and hyperextension exercises are advised. However, sports associated with jumping, marked stress and functional overuse of the back, especially in patients with thoracolumbar and lumbar Scheuermann’s kyphosis, should be discouraged. Few series with a small number of patients treated with superficial electrical stimulation have been reported on this therapeutic modality.

Bracing may be used in skeletally immature patients with radiographically diagnosed early stages of Scheuermann’s disease. Bracing should be used to treat the deformity and not to resolve pain. The most commonly used brace is the Milwaukee brace, which acts as a three-point dynamic orthosis promoting extension of the thoracic spine. It is especially indicated in kyphotic curves with an apex between T6 and T9, where only the use of this type of brace has proven beneficial long-term results in decreasing kyphotic curves in patients significantly away from growth maturity. The compliant patient must wear the brace on a full time basis (22 of 24 hours daily), for an average of 1 year (12-18 months). Many authors recommend that the patient continue the brace treatment part-time, usually at night until skeletal maturity.

In most series, the results of bracing are usually excellent in compliant patients, with approximately 50% of correction. After bracing is discontinued, some loss of correction should be expected, but in the majority of cases, the deformity is improved and the curve correction is maintained. Progression of the deformity, requiring other type of conservative treatment or surgical intervention, is more likely observed in patients with poor brace compliance, in kyphotic curves of more than 74° to 75°, in patients with severe and rigid curves and in atypical forms of the disease.

Other types of bracing are the active-passive Gschwend erection corset, the low profile braces for thoracolumbar kyphosis and thoracic kyphosis with an apex below T9 and the four-valve orthosis suggested by Zielke for flexible curves with a curve apex below T9 after cast treatment. These devices were especially designed and manufactured to relieve the psychological problems caused by the Milwaukee brace’s occipital-chin ring to the patient. The lumbar form of Scheuermann’s kyphosis, responds well to the application of a lumbar orthosis. Complications of brace treatment are not reported, except from the psychological problems of full-time brace wearing during adolescence.

Corrective casts have been used by many surgeons in the conservative treatment of Scheuermann’s kyphosis of increased rigidity before switching to a brace, or preoperatively in cases requiring surgical correction. Many types of casts have been used, such as plaster casts, tantigravity or localizer-type casts, and elongation casts or Halo traction for preoperative correction. Also, various therapeutic schemes such as the Lyon method have been reported with various results. Although casting achieves a lesser initial mean correction of the kyphosis, it provides better long term angular correction, with lower loss of correction and lesser deterioration.

It is crucial to preserve the initially achieved correction with casts by continuing treatment with a Milwaukee brace, and it is not acceptable to undertake cast treatment after skeletal maturity.

Surgical treatment of Scheuermann’s kyphosis is rarely necessary. Murray et al studied 67 patients treated conservatively for Scheuermann’s kyphosis and found a less ominous natural history of the disease; they suggested a re-examination of the indications of operative treatment. Many other series have used different criteria in the selection of patients for surgical correction of the kyphosis. These criteria include kyphoses >70°, progression of the kyphosis despite bracing, substantial kyphotic deformities in skeletally mature patients, severity of localized and chronic pain refractory to conservative treatment, neurologic complications and the presence of deformity with regard to the importance of cosmetic appearance, self-esteem, and self-consciousness of the growing adolescent.

Posterior operative technique is historically the first surgical method applied in the treatment of Scheuermann’s kyphosis, with satisfactory results in kyphotic correction and relief of symptoms. Posterior spine instrumentation and arthrodesis has been performed for kyphotic curves of <70°. A flexible kyphotic curve that is corrected to approximately 50° in the preoperative correction methods and radiographic techniques could be managed with a posterior-only surgical technique. The Harrington rods compression system has been used successfully for the compression across the apex and the elongation of the concavity of relatively flexible kyphotic curves. The disadvantages observed with this type of spine instrumentation include the frequently observed loss of correction, the increased curve stiffness in adult patients, and the high degree of pseudarthrosis documented in the posterior surgical correction of kyphoses >70°.10 The Harrington-Cotrel, the Luque, and the Cotrel-Dubousset are other posterior compression systems used in Scheuermann’s kyphosis. Biomechanical segmental instrumentation systems appear better than the other spine instrumentation systems, and currently they are the most frequently used systems.

The frequently observed loss of correction with posterior-only techniques, and the increased rigidity of the >75° kyphotic curves in adult patients led to the use of combined anterior release and posterior spine arthrodesis with instrumentation. Anterior release and posterior instrumentation has also been used in the treatment of skeletally immature patients with curves of >65°. Many series using combined approaches, have reported excellent results, with decrease of the kyphotic angle and low rates of loss of the correction initially obtained. These benefits are achieved by release of the anterior longitudinal ligament, which becomes contracted and thickened in severe Scheuermann’s disease, complete diskectomy in several disk spaces, excision of osteophytes that can completely bridge vertebral interspaces and bone grafting. The decision between a posterior-only or a combined surgical approach is taken with the careful preoperative evaluation of the patient.

Some surgeons perform the combined approach as a one-stage procedure, while others prefer a two- or three-stage surgery. Anterior techniques are performed via an intrathoracic approach for thoracic curvatures and via a thoracoabdominal retroperitoneal approach for thoracolumbar kyphoses.

Various types of anterior distraction systems, such as the Dunn, Kostuik-Harrington and Gardner systems have been proposed for the intraoperative or permanent curve distraction in cases of increased vertebral rigidity.

Video assisted thoracoscopic surgery is a promising new technique in the treatment of kyphosis, as an alternative to open thoracotomy in anterior release procedures. This technique is more expensive than open thoracotomy, but with fewer complications, mostly pulmonary and intercostals neuralgias, decreased pain and perioperative morbidity, shorter hospital stays, and fewer intensive care days. However, there is little experience with this new technique, and further prospective studies are needed to determine its benefit and therapeutic outcome in patients with Scheuermann’s disease.

The selection of fusion levels remains a critical part in the surgical treatment of kyphotic spinal deformities. It is recommended that arthrodesis must include the end vertebra of the curve proximally and extend to the L1 vertebra distally. In the typical type I Scheuermann’s kyphosis, spine arthrodesis must be performed from T3 to L2. It is also reported that despite of an apparently adequate arthrodesis length, the posterior distractive forces may lead to postoperative junctional kyphosis.

The use of the modern multisegmental rod, hook, and screw instrumentation and the heightened awareness of the potential complications have increased the safety in the surgical treatment of Scheuermann kyphosis. In posterior-only procedures, the most frequent complications are pseudarthrosis, hardware failure or hook pull-out, and loss of correction.

Other complications reported in both posterior and combined techniques, include junctional kyphosis, wound infections, neurologic deficits, painful bursitis over prominent hardware, pressure sores under casts, deep vein thrombosis and pulmonary embolism, cardiopulmonary problems, pulmonary complications such as pneumothorax or hemothorax, gastrointestinal disorders, postoperative back pain or sciatica, dural lacerations, infected dural fistulas and postoperative meningitis and encephalitis. Care must be taken not to divide the segmental spinal arteries bilaterally and to monitor the spinal cord with somatosensory evoked potential monitoring and wake-up tests. The introduction of the rods should also be careful, as it may lengthen the anterior column and stress the spinal cord and its blood supply. Corrective maneuvers for spinal deformities have various effects on the spinal canal length and although they do not directly pose distraction forces, they indirectly lengthen the spinal canal. Superior mesenteric artery syndrome is a rare cause of small bowel obstruction in both adult and pediatric populations after correction of kyphotic deformities.

Scheuermann’s kyphosis is a relatively common spine deformity with specific radiological findings that usually responds to conservative treatment. The indications for the treatment of Scheuermann’s kyphosis include persistent back pain, progressive kyphotic deformity, and poor cosmetic appearance.

Brace treatment, usually with a Milwaukee brace, is recommended in skeletally immature patients with flexible kyphotic curves of < 65°. Operative treatment is rarely indicated. Indications include pain and degenerative changes in adults and progressive deformity despite brace treatment and curves >65° in adolescents. Posterior spine arthrodesis and segmental compression instrumentation are effective in correcting and stabilizing kyphotic deformity in Scheuermann’s disease. Combined anterior and posterior spine arthrodesis is recommended for rigid kyphotic deformities that are not corrected to < 60° on hyperextension.