Scheuermann Kyphosis

Updated: Aug 16, 2016
  • Author: Clifford Tribus, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Overview

Background

In 1920, Scheuermann first described the clinical findings of structural thoracic kyphosis. However, it was not until 1964 that Sorensen defined the radiographic findings in Scheuermann kyphosis. [1] He described the defining characteristic of anterior wedging of 5° or more in at least three adjacent vertebral bodies. This helped to objectify and differentiate Scheuermann kyphosis from postural round-back deformity.

Scheuermann thoracic kyphosis is a structural deformity of the thoracic spine, defined by anterior wedging of at least 5° of three or more adjacent thoracic vertebral bodies. Further radiographic findings include Schmorl nodes and endplate narrowing. Although the etiology of Scheuermann kyphosis (Scheuermann disease) remains unknown, the natural history and treatment indications are well described. [2]

Both adolescents and adults can develop symptoms associated with Scheuermann kyphosis. Adolescents typically develop a progressive cosmetic deformity, which first brings them in for medical attention, whereas adults with long-standing deformity typically develop pain as an indication for treatment.

Bracing has been demonstrated to be an effective treatment modality for the adolescent with a progressive deformity, whereas pain often responds to nonoperative care, including physical therapy and anti-inflammatories in both adolescents and adults. In patients with a progressive deformity, refractory pain, or neurologic deficit, surgical correction may be indicated.

Historically, surgical care of Scheuermann kyphosis (Scheuermann disease) has shadowed surgical care of idiopathic scoliosis. The role of surgical care for adolescent kyphosis was debated in the sparse literature before 1960. In 1962, Paul Harrington introduced the Harrington rod to augment the surgical correction of scoliosis. In 1965, Moe presented his nonoperative and operative results from a posterior approach in the treatment of adolescent kyphosis. Postoperative curve progression and a high pseudoarthrosis rate complicated the posterior-only approach. [3]

Combined anterior and posterior surgical approaches for Scheuermann kyphosis were first popularized in the 1970s. These techniques increased fusion rates and correction and remain the foundation of current surgical approaches. Subsequent innovations included simultaneous thoracoscopic anterior release with postinstrumented fusion.

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Pathophysiology

Although the etiology of Scheuermann kyphosis (Scheuermann disease) is not yet understood, the histologic and pathologic findings are well described. Radiographically, the presence of three adjacent wedged vertebral bodies of at least 5° each is pathognomonic for Scheuermann kyphosis. Anatomic findings include a thickened anterior longitudinal ligament (ALL) with narrowed intervertebral disks. The vertebral bodies are wedged, and traumatic disk herniations through the endplates are consistent findings.

The ratio of collagen to proteoglycans in the matrix of the endplate in patients with Scheuermann kyphosis has been described as low in comparison with that in patients without the condition. This relative decrease in collagen has been hypothesized to lead to an alteration in the ossification of the endplate and, thus, to altered vertebral body growth.

Finally, osteoporosis has been postulated to have a role in the pathology and etiology of Scheuermann kyphosis. Bradford reported on 12 patients with Scheuermann kyphosis who were prospectively studied with an extensive osteoporosis workup, including an iliac crest biopsy. [4] Some of the patients with Scheuermann kyphosis were demonstrated to have a mild form of osteoporosis, although the cause and effect of this finding in terms of developing Scheuermann kyphosis was not made.

A follow-up study by Gilsanz reported 20 adolescent patients aged 12-18 years with Scheuermann kyphosis who demonstrated no evidence of osteoporosis as measured by quantitative computed tomography (CT). [5]

Bradford, however, had surmised that the osteoporosis was transient and somehow led to altered vertebral growth and, thus, to the formation of Scheuermann kyphosis. [4] This etiologic hypothesis remains a subject of debate.

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Etiology

The proximate cause of Scheuermann kyphosis (Scheuermann disease) has not yet been determined. Scheuermann initially hypothesized that avascular necrosis of the ring apophysis led to premature cessation of growth anteriorly and subsequent wedging of the vertebral body. Schmorl later postulated that traumatic herniations of disk material through the vertebral endplates led to subsequent loss of disk height and anterior vertebral wedging. Both of these theories were disproved later.

Halal reported on five families in which Scheuermann kyphosis appeared to transfer in an autosomal-dominant mode of inheritance. [6] To date, the genetic marker has not been determined.

Skogland [7] and Ascani [8] proposed other theories that Scheuermann kyphosis is based on a genetic inheritance. [7] Skogland reported on 62 females aged 9-18 years, whose mean height was an average of 2.5 standard deviations (SDs) above average. Of these 62 females, 18 had thoracic kyphosis of more than 40°, with 11 additional participants having vertebral anomalies consistent with Scheuermann kyphosis.

Ascani also presented work demonstrating a similar correlation between Scheuermann kyphosis and height. He also demonstrated increased levels of growth hormone. [8]

Damborg et al found a heritability of 0.74 in Scheuermann's disease, with a lower threshold in men than women. [9]

A study by Hershkovich et al suggested that height and body mass index (BMI) are associated with the risk and severity of spinal deformities in adolescents. [10] 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 in underweight males and females, spinal deformities were significantly more common and were more likely to be severe. Greater height was also associated with increased risk and greater severity of spinal deformities in males and females.

Mechanical factors have been postulated as a cause for Scheuermann kyphosis. [11] Scheuermann initially noted a higher incidence of kyphosis in industrial workers and found that hyperextension bracing is helpful in curbing the progression of Scheuermann kyphosis, which would support a mechanical etiology. However, the radiographic and histologic changes of Scheuermann kyphosis have not yet been demonstrated to be in fact secondary or primary in the development of Scheuermann kyphosis.

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Epidemiology

The prevalence of Scheuermann kyphosis (Scheuermann disease) is estimated to be 4-8% of the general population. Sorensen reported a prevalence of 0.4-8.3%. [1] Scoles et al reported on 1384 cadaveric specimens and noted a 7.4% prevalence of Scheuermann kyphosis. [12]

Although the prevalence of Scheuermann kyphosis is generally accepted as being essentially equal in males and females, there is some debate regarding this finding in the literature. Bradford et al reported a female-to-male ratio of 2:1 for Scheuermann kyphosis. [13, 14] Meanwhile, Murray et al reported the exact opposite finding, with a 2.1:1 male-to-female ratio. [15] In Sorenson's work, 58% of the patients were male, and 42% were female. [1]

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Prognosis

Outcome and prognosis depend on the individual patient and treatment rendered. Generally, a patient with moderate-to-mild Scheuermann kyphosis (Scheuermann disease) rarely requires surgery or even bracing. These patients can be managed with education, guidance, and overall encouragement to resume and maintain normal activity levels. Aggressive use of exercise and judicious use of anti-inflammatory medications can augment this regimen.

The outcome and prognosis of bracing treatment is more controversial. While the brace is in place, approximately a 50% correction of the deformity should be expected. However, once the brace is removed, a gradual loss of correction is expected over time.

Sachs et al reported on 120 patients reviewed 5 years after discontinuance of bracing [16] ; 69% of these patients had maintained at least 3° of improvement over their presenting radiographs. Other authors have presented similar results. Sachs also reported that the prognosis was less favorable if the presenting curve was 74° or more. One third of these patients failed bracing therapy and progressed to needing surgery.

The current literature largely lacks patient-based outcome studies in patients who have undergone surgical correction of Scheuermann kyphosis, though a number of retrospective reviews have reported high patient satisfaction ratings, as have some studies with insufficient numbers of control subjects. Surgical correction of the deformity affords predictable restoration of normal thoracic kyphosis, thus halting progressive deformities. Reasonable pain relief and resumption of normal activities also are reflected in multiple retrospective reviews.

Graat et al carried out a cohort study that assessed long-term (mean follow-up, 18 years) clinical and radiologic outcomes in 29 patients who underwent surgical treatment of Scheuermann kyphosis via either a posterior approach (n=13) or a combined anterior-posterior approach (n=16). [17]  They obtained disappointing radiologic results, but these did not correlate with clinical outcome scores, which were good. Outcomes were better with the combined approach than with the posterior approach.

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