Scheuermann Disease - Clinical Tree

Summary of Key Points

Other names include Scheuermann kyphosis (Scheuermann thoracic kyphosis), Calve disease, idiopathic juvenile kyphosis of the spine, and juvenile discogenic disease.
Scheuermann kyphosis is the most common cause of hyperkyphosis in adolescents aged 12 to 17 years.
Although the proximate etiology remains largely obscure, there is evidence for a substantial genetic contribution.
The natural history of Scheuermann kyphosis is still controversial and not well documented, with conflicting reports on the severity of pain and physical disability.
The thoracic spine is the most commonly involved region; the thoracolumbar or lumbar spine regions can be involved as well.
The radiographic criterion for Scheuermann kyphosis includes hyperkyphosis greater than 40 degrees of the thoracolumbar spine, identified by anterior wedging of greater than or equal to 5 degrees in three or more contiguous vertebral bodies.
Treatment of Scheuermann kyphosis is nonoperative in most situations; however, it should include a multidisciplinary approach.
Surgical treatment of Scheuermann kyphosis can be posterior spinal fusion, anterior spinal fusion, or a combination, with the former being the most common approach.

History

In 1920, Holger Werfel Scheuermann, a Danish surgeon, first described the clinical findings of a structural, rigid kyphosis of the thoracic or thoracolumbar spine occurring in adolescents. Scheuermann’s concept of this disease was a painful, abnormal, fixed arcuate or dorsal kyphosis developing around puberty because of wedging of one or more vertebrae from disturbances of the vertebral end plates and showing peculiar radiographic characteristics. ^, Scheuermann initially hypothesized that avascular necrosis of the ring apophysis led to premature cessation of growth anteriorly and subsequent wedging of the vertebral body (VB). Schmorl later postulated that traumatic herniation of disc material through congenital indentations of the disc in the region of the nucleus pulposus into the vertebral end plates led to subsequent loss of disc height and anterior vertebral wedging. ^, Even in the face of such pertinent theories, the proximate cause of Scheuermann kyphosis still remains to be determined.

Because of the variability of its clinical features, the radiological characteristics of Scheuermann disease (SD) have been more accepted as indicators of the disease. These were initially described by Butler as follows: wedge-shaped VBs, increased anterior-posterior diameter of the VB, irregularly shaped and narrowed disc spaces, kyphosis or loss of lordosis, Schmorl’s nodes, a flattened area on the superior surface of the VB in the region of the epiphyseal ring anteriorly, and a detached epiphyseal ring anteriorly. Butler also pointed out that in the milder or localized forms of SD there may not be any deformity, and that all parts of the spine can be affected.

In 1964, Sorensen explicated the radiographic findings in SD to the now widely accepted radiographic criteria of: thoracic hyperkyphosis greater than 40 degrees and irregular upper and lower vertebral end plates with loss of disc space height, involving at least three adjacent wedged vertebrae, angled by 5 or more degrees. This definition helped to objectify and differentiate Scheuermann kyphosis from postural round-back deformity.

Taylor et al. further subclassified the characteristics into major––end plate irregularity, wedging (>5 degrees), and sagittal overgrowth (increased anteroposterior diameter of the VB)––and minor––Schmorl’s nodes, anterior flattening of the vertebral end plate (a lesser degree of wedging), and anterior detachment of a ring apophysis.

Both adolescents and adults can develop and present with symptoms associated with Scheuermann kyphosis, including a progressive cosmetic deformity and a longstanding, painful deformity, respectively.

The controversy on the natural history of SD has always been reflected in the treatment modality options put forward for the condition. The proponents of a benign natural history of thoracic SD initially suggested that the condition did not need treatment, citing uncertainty on whether orthotics or surgical treatments could prevent any of the consequences.

Beyeler et al., however, reported considerable improvement of the kyphotic deformity with exercises alone, but only in the skeletally immature patient. Bracing with the Milwaukee brace or, more rarely, a Risser antigravity cast, was used as an effective treatment modality for adolescents with progressive deformity, patients with more severe deformities (>40 degrees), and those with more extensive radiographic vertebral changes.

For pain symptoms, nonoperative modalities, such as physical therapy and antiinflammatory drugs, were employed with good results in both adolescents and adults.

Surgical care for Scheuermann kyphosis is indicated for patients with a progressive deformity, pain that is refractory to nonoperative modalities, or neurological deficit(s). Its approach has historically shadowed that of idiopathic scoliosis (IS). A short while after debate of the role of surgical care for Scheuermann kyphosis in 1960, and after the introduction of Harrington rods by Paul Harrington in 1962 to augment the surgical correction of scoliosis, Moe presented the results of a comparative study of outcomes of nonoperative care versus an operative posterior-only approach for the treatment of adolescent kyphosis. The results showed that the posterior-only operative approach was complicated by postoperative curve progression and a high pseudarthrosis rate. ^,

This paved the way for the popularization of a combined anterior and posterior surgical technique for Scheuermann kyphosis in the 1970s, which resulted in increased fusion rates and correction. This approach remains the foundation of surgical approaches today, as well as subsequent innovations such as a hybrid combination of an initial thoracoscopic anterior release with a posterior instrumented spinal fusion.

Nomenclature

In 1920, Scheuermann described a painful kyphosis of the thoracic spine in a 16-year-old farmhand and named the disorder “kyphosis dorsalis juvenalis (a juvenile dorsal kyphosis).” The condition was later on named SD, after him. Subsequently, a number of titles/names have been used to refer to SD, including: juvenile kyphosis, adolescent kyphosis, apprentice’s kyphosis, Scheuermann juvenile kyphosis, osteochondritis, osteochondritis deformans juvenilis dorsi, vertebral osteochondritis, and spinal or vertebral osteochondrosis. Although it was referred to as “osteochondritis” attributed to the thought of an inflammatory nature of its origin, studies subsequently showed no evidence of inflammation but rather disorderly growth demonstrated by an irregular and patchy transition from cartilage to bone. ^, Spinal osteochondrosis is probably the most accurate and most accepted of all terms used for this disease to date. For purposes of continuity in literature, the name “Scheuermann disease” has continued to be used commonly.

Clinically Relevant Embryology of the Vertebral Column

The notochord and somites are the most significant structures responsible for the development of the future vertebral column. The vertebrae develop from mesenchymal cells derived from the sclerotomes of the somites. During the fourth week, these cells of the sclerotome begin to migrate toward and surround the neural tube and the notochord. Once the sclerotomes have surrounded the notochord and the neural tube, each level will separate into a cranial area of loosely packed cells and a caudal area of densely packed cells. Each vertebra is formed by fusion of the condensation of the caudal half of one pair of sclerotomes with the cranial half of the subjacent pair of sclerotomes.

The area between the two halves in a single level of the sclerotome was described by O’Rahilly as a “cell-free space.” This “space” will fill with cells migrating cranially from the caudal densely packed sclerotome layer to form the annulus fibrosus.

As the bodies of the vertebrae form, the notochord degenerates, save for small portions that persist at the levels between adjacent VBs. These portions expand to form a gelatinous center, the nucleus pulposus, which, together with the annulus fibrosus, forms the respective intervertebral discs.

Postnatal Development of the Vertebral Column

During the fetal period and at birth, the normal curve of the vertebral column is kyphotic. This primary curvature continues within the thoracic region throughout development to maturity. The cervical and lumbar lordotic curvatures develop secondarily during infancy. Lordosis in the cervical vertebrae develops as a result of the infant holding its head upright, whereas lumbar lordosis develops as a result of the infant achieving a sitting and then standing posture.

Sagittal Spinal Alignment and Deformity

Knowledge of the principles of sagittal alignment is critical in management of spinal deformity, Scheuermann kyphosis included. Sagittal spine alignment during growth differs from alignment during adulthood. It is only when the child becomes a teenager that the definitive sagittal curves are acquired. The average thoracic kyphosis increases from 20 degrees in childhood to 25 degrees in teenage years and 40 degrees in adulthood. There is also a great variety of normal sagittal profiles. The range of normal thoracic kyphosis is between 10 degrees and 50 degrees, increasing in the elderly. A spinal deformity is considered when the curve is greater (or lesser) than the mentioned degrees. Scheuermann kyphosis, in particular, is commonly considered in cases with a thoracic hyperkyphosis greater than 40 degrees.

The concept of pelvic incidence was introduced by Duval Beaupere. This is the angle made by the line joining the middle of the sacrum to the hip joint, with the other line perpendicular to the sacral plateau. It is the only sagittal parameter that is fixed in each individual. Pelvic incidence has been shown to correlate with the sagittal balance of the patient, and, as a rule of thumb, pelvic incidence should be approximately 10 degrees less than the lumbar lordosis. To date, however, no study has reported results on any possible relationship between increased pelvic incidence and Scheuermann kyphosis.

Epidemiology

Prevalence

There is a relatively large discrepancy in the reported prevalence estimates of Scheuermann kyphosis because of the variability in diagnostic criteria used by different authors, depending on whether clinical criteria alone, a combination of clinical and radiological criteria, or radiological criteria alone were used. Sorensen reported a prevalence of 0.4% to 8.3% in the population. Although Bradford noted a prevalence as great as 10%, Baker in his review of SD in the same year estimated the prevalence of people affected as being between 20% and 30%. Scoles et al. in their study on 1384 cadaveric specimens reported a prevalence of 7.4% of the disease, and Damborg et al. reported an overall prevalence of 2.8%. In the United States, the accepted prevalence rate of this disease is 0.4% to 8% in the general population. ^, ^,

In 27 centers across Europe that participated in the European Vertebral Osteoporosis Study, although it was highly variable between the centers, the prevalence of SD in age-stratified population-based samples of over 10,000 men and women aged 50 years and above averaged 8% in both sexes.

Incidence

A recent review of trends in treatment of Scheuermann kyphosis by Horn et al. reported a statistically significant increasing incidence from 3.6 to 7.5 per 100,000 between 2003 and 2012.

Gender Ratio

In the past, SD was thought to be more common amongst males than females. Scheuermann ^, himself considered that the disease almost exclusively affected boys, and Wassmann cited Holund’s study, based on Scheuermann’s patients, to support his conclusion that SD mainly affects males. Subsequently, however, many authors have not found an appreciable difference in the sex ratio, whereas some have actually reported a greater number of females than males affected by the disease. A review of 1338 cases by Sorensen, in which 58% of the patients were male and 42% were female, concluded that there was not a distinct sex difference. Bradford et al. concurred with this opinion, despite the fact that in their 1974 study of patients with SD ( n = 168) the female-to-male ratio was 2:1.

In the multicenter European study by Armbrecht et al., the overall prevalence was 8% across both sexes, and, using multivariable models adjusted for center, the diagnosis of Scheuermann kyphosis was still not associated with sex.

Additionally, varying male-to-female prevalence ratios have been reported in other studies: 1:2, 1:1, 1.7:1, 2:1, ^, and 7.3:1. It suffices to say, therefore, that, deducing from the currently available literature, males are neither more nor less likely than females to have SD. ^, ^, ^,

Associated Conditions

Lumbar hyperlordosis – Many patients with SD have an excessive lordotic curve in the lumbar spine; this is the body’s natural compensatory response to the kyphotic curve above. ^, ^, ^, ^, ^,
Scoliosis – In addition to the more common lordosis, between 15% and 30% of SD cases demonstrate varying degrees of structural scoliosis, ^, ^, although most cases are negligible. Blumenthal and associates noted an 85% rate of lumbar scoliosis among 50 patients with type I SD. In more severe cases, however, the combination is classified separately as kyphoscoliosis.
Spondylolysis – There is an increased occurrence of spondylolysis (6%) in the lumbar spine in patients with thoracic Scheuermann kyphosis. ^, Ogilvie and Sherman also observed a 50% prevalence of asymptomatic spondylolysis among 18 patients with type I disease. The hypothesis is that the excessive compensatory lumbar hyperlordosis places stress on the pars of the L4 and L5 vertebrae, resulting in the spondylolysis.
Spondylolisthesis – Spondylolisthesis in the lumbar spine is also common in patients with thoracic Scheuermann kyphosis.
Altered chest physiology – Many patients with SD have very large lung capacities, and males often have broad, barrel chests. Most people have forced vital capacity (FVC) scores above average. It has been proposed that this is the body’s natural way to compensate for a loss of breathing depth.
Tight hamstrings – Oftentimes SD patients have tight hamstrings, which, again, is related to the body compensating for excessive spinal curvature. However, some authors actually suggest that the tightness of the hamstrings is actually the initial cause of sagittal decompensation and ultimately results in the growth abnormality. ^,

Age

SD affects the growing, maturing spine and is usually identified in adolescents between 11 and 17 years of age. The typical age of onset of Scheuermann kyphosis is from 10 to 12 years, before puberty after the ossification of the vertebral ring apophysis. It then becomes most prominent during the adolescent growth spurt as a structural kyphotic deformity of the thoracic or thoracolumbar spine. ^, The disease usually emerges between the late juvenile period and 17 years of age, most commonly between 12 and 15 years. ^, The diagnosis is rarely made in patients younger than 10 years.

Of note also is that the initial case described by Scheuermann in 1920 was in a 16-year-old farmhand, and in two recent studies of patients with Scheuermann kyphosis that underwent treatment, the average age reported for these patients was 16.0 (range 13.0–24.1) and 16.1 ± 2.13.

Scheuermann kyphosis is the most common type of structural kyphosis in adolescents, and SD is the third most common cause of back pain in children and adolescents after spondylolysis and spondylolisthesis.

Despite the fact that Scheuermann kyphosis is most commonly diagnosed in adolescents, adults can also develop symptoms associated with it. Whereas the former typically present initially for treatment for a progressive cosmetic deformity, the latter, with longstanding deformities, typically develop pain as an indication for treatment.

Location

The apex of the “classic” Scheuermann kyphosis is located at the midthoracic spine; in other cases, it may involve the lower thoracic spine or the thoracolumbar junction. ^,

Classification

Type I (Classic) – Thoracic spine involvement only, with the apex of curve at T7–T9.
- Most common form
- Curve from T1–T2 to T12–L1
- Better prognosis
Type II – Thoracic and lumbar involvement, with the apex of curve at T10–T12.
- Far less common form
- Curve from T4–T5 to L2–L3
- Associated with increased back pain
- More likely to be more progressive and symptomatic
- More irregular end plates noted on radiographs, less vertebral wedging
Edgren and Vainio first described similar vertebral changes that may occur in the lumbar spine (atypical Scheuermann, lumbar Scheuermann or Type III Scheuermann) ^, ( Fig. 22.1 ).

The cervical form of SD has not been described. It might be explained by the uncus, which is not mobile during puberty and could protect the vertebral end plate against mechanical stress. ^,

Genetics

A familial occurrence of SD has been described in earlier studies, ^, and inheritance through a dominant gene in a biallelic model was described in a 2001 study by Axenovich et al. Graat et al. provided further support for the genetic etiology hypothesis in their report of classic SD in a set of monozygotic male twins. Damborg and associates in their 2006 review of a large twin cohort of almost 35,000 individuals also found that the concordance for monozygotic twins was significantly greater than that for dizygotic twins, and that the hereditability was 74%. These findings suggest a strong genetic contribution to the etiology of SD.

Etiopathogenesis

SD is characterized by defective growth of the vertebral cartilage end plate. The vertebral end plate is the physical shield separating the disc from the vertebra; it is composed of a cartilaginous and an osseous component. As a mechanical interface between the stiff bone and resilient disc, the end plate is the weakest portion of the disc–vertebra complex and is predisposed to mechanical failure. ^, It is also the main gateway for nutrient supply to the disc, which is not vascularized.

Although the exact etiopathogenesis as it relates to SD is still undetermined, genetic inheritance as well as or resulting in discordant vertebral end plate mineralization and ossification has been suggested as a more likely primary influence on the occurrence of the weakened end plate associated with SD.

Genetic Background

The weakness of the vertebral end plate likely results from a predisposing genetic background that influences the quality of matrix components (collagen types II and IX) and chondrocytes. Earlier studies have indicated a major genetic contribution. ^, An autosomal dominant form of inheritance is suspected. The main candidate genes are COL2A1 and COL9A3 . An Arg-75-Cys mutation in COL2A1 was found to be associated with a spondyloepiphyseal dysplasia similar to SD with severe osteoarthritis, ^, and a mutation in COL9A3 was found in patients reporting low back pain with radiographic Scheuermann kyphosis and end plate lesions. ^, The role of COL1A1 and COL1A2 that was initially suspected was not confirmed.

Oei et al. also conducted a genome-wide association study for radiographic SD where they found a single nucleotide polymorphism associated at genome-wide significance level with SD mapping to TLL1 . Of note, TLL1 encodes a protease that shares structural similarity with bone morphogenetic protein 1, which is involved in collagen and chordin synthesis and can induce formation of cartilage in vivo. In spite of the limited study sample size because of the relatively low prevalence of the disease, these results still contribute to the theory of genetic contribution to the etiology of SD.

Disorganized Endochondral Ossification

Histological studies show disorganized endochondral ossification, reduced collagen level, and increased mucopolysaccharide levels in the end plates with the disease. ^, ^, The main hypothesis is that disorganized endochondral ossification results from defective growth of the cartilage end plate. The relative decrease in collagen has also been hypothesized to lead to an alteration in the ossification of the end plate.

Consequently, as a result of excessive mechanical stress on a low-quality/weakened vertebral end plate during growth of the spine, this causes disc impairment and disproportional VB growth, with resultant classic wedge-shaped VBs that will lead to kyphosis.

Mechanical Factors

Repetitive Strain

The degree of mechanical stress influences the severity of spinal impairment in SD. This is supported by the following observations: firstly, one study reported similar lesions of localized lumbar osteochondrosis in twin sisters that were worse in the twin who practiced strenuous sports activities. Secondly, the prevalence of SD seems to be higher in manual workers who began work at a young age and in high-level athletes whose sports involve large motions of the trunk in flexion/extension. Finally, repetitive strain on vertebral end plates in young rats led to typical Scheuermann lesions.

Stature of the Sternum

Fotiadis and colleagues, investigating the length of the sternum of 10,057 students, found that 175 adolescents with SD had a short sternum. This short sternum might result in excessive compressive forces on the vertebral end plates anteriorly, thereby allowing uneven growth of the VBs with wedging. This sternal feature may also be associated with a particular genetic background. Further studies are required, however, for the documentation of this theory of pathogenesis.

Osteoporosis

Childhood/juvenile osteoporosis has been postulated to have a role in the etiopathogenesis of Scheuermann kyphosis. In a study of 12 patients with Scheuermann kyphosis who were prospectively studied with an extensive osteoporosis workup, including an iliac crest biopsy, Bradford reported that some of the patients with Scheuermann kyphosis had a mild form of osteoporosis, although the cause and effect of this finding in terms of developing Scheuermann kyphosis was not stated. A follow-up study by Gilsanz, however, reported 20 adolescent patients aged 12 to 18 years with Scheuermann kyphosis who demonstrated no evidence of osteoporosis as measured by quantitative computed tomography (CT). Bradford, however, had surmised that the osteoporosis was transient and somehow led to altered vertebral growth, and thus to the formation of Scheuermann kyphosis. This etiological hypothesis remains a subject of debate.

Height and Body Mass Index

Skogland et al. carried out a prospective study of 62 girls aged 9 to 18 years whose height was an average of 2.5 standard deviations above average. Thirteen of them had scoliosis measuring 10 degrees or more. Eighteen girls had thoracic kyphosis of more than 40 degrees, and 11 had additional vertebral anomalies consistent with SD. The values for both scoliosis and SD in this group were much higher than those in the rest of the population.

Ascani had earlier on presented his work demonstrating a similar correlation between Scheuermann kyphosis and height. He also demonstrated increased levels of growth hormone.

Fotiadis et al. postulated that a high body mass index may be another risk factor for SD. In their study involving 175 adolescents between 11 and 17 years old who were diagnosed with SD, their weight, height, and body mass index (BMI) were significantly higher than those of an equal number of individuals in the control group, which was comparable concerning age and sex. However, they indicated that the exact role of height and weight remains unknown, because these did not seem to affect the magnitude and morphology (Voutsinas index) of the main kyphotic curve in the SD patients.

Linthoudt and Revel also hypothesized that overweight results in excessive mechanical stress on growing VBs. Interestingly, though, two studies suggested that the apparent association between SD and overweight could be attributed to increased weight and height secondary to genetically-based hormonal disturbances. ^,

Hershkovich et al. also concluded that height and BMI are associated with the risk and severity of spinal deformities in adolescents. The study, which included 103,249 males and females aged 17 years who had been diagnosed with some degree of kyphosis or scoliosis, found that greater height was also associated with increased risk and greater severity of spinal deformities in males and females. However, they found that these spinal deformities were significantly more common and more likely to be severe amongst underweight males and females.

Other components that have also been suggested to explain or partially explain this condition include: growth hormone hypersecretion, defective formation of collagen fibrils with subsequent weakening of the vertebral end plates, dural cysts, trauma, biomechanical stressors such as tight hamstrings, vitamin A deficiency, poliomyelitis, and epiphysitis. ^, ^,

Pathophysiology

SD may result from excessive mechanical stress on a weakened vertebral end plate during growth of the spine. The most common findings associated with this disease include thoracic spine hyperkyphosis (because of vertebral wedging), as defined by the diagnostic criteria, commonly associated with irregular vertebral end plates, Schmorl’s nodes, and disc impairment or loss of disc space height ( Fig. 22.2 ).

Fig. 22.2, A, The elementary radiographic lesions of Scheuermann disease: vertebral wedging, Schmorl’s node, irregular vertebral end plate, impaired ring apophysis, impaired disc. B, Thoracic form of Scheuermann disease. Vertebral wedging and irregular vertebral end plate.

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