SCHEUERMANN DISEASE
Although an exaggerated thoracic kyphosis has been documented for centuries, it was only with the advent of medical radiography that Scheuermann identified the disease. This progressive disorder occurs in patients near puberty, manifested by an increase in the normal kyphosis in the thoracic spine with an abnormal degree of wedging of the vertebrae at the apex of the kyphotic curve. The diagnosis of Scheuermann disease is limited to patients with a kyphotic curve greater than 60 degrees. (Measurements are done in a manner similar to the coronal plane Cobb method; see Plate 1-40.) Typically the curve is measured from T4 to T12 on the lateral view. Normal kyphosis is 20 to 45 degrees in which at least three adjacent vertebrae are wedged 5 degrees or more and where disc space narrowing and end plate irregularity are noted. Although Schmorl’s nodules are common radiographic findings, they are not part of the diagnostic criteria of Scheuermann disease.
The etiology of Scheuermann disease is not yet understood, but there
appears to be a genetic factor. Scheuermann speculated that the disease was
caused by avascular necrosis of the anterior portion of the cartilage ring
apophysis of the vertebral body, similar to the pathogenesis of
Legg-Calvé-Perthes disease. Mechanical factors (particularly heavy labor),
contractures of the hamstring and pectoral muscles, and herniation of the
intervertebral disc through the anterior portion of the epiphyseal plate have
also been suggested as contributing factors. Specimens obtained from patients
undergoing anterior spinal fusion for Scheuermann kyphosis have revealed
wedge-shaped vertebral bodies and a contracted, thickened anterior longitudinal
ligament that acts as a tether across the kyphosis, maintaining a relatively
inflexible deformity. Subsequent histologic studies, while confirming a
disruption of the epiphyseal plates and extravasation of disc material into the
bony spongiosa of the vertebral body, have revealed no evidence of avascular
necrosis or inflammatory changes in bone, disc, or cartilage.
Clinical Manifestations. Characteristic signs
of Scheuermann disease are the exaggerated, rounded appearance of the back,
round shoulders, and poor posture; pain and deformity are uncommon. In
adolescents, so-called poor posture may be an important clue to significant
structural alterations of the vertebral column that can only be identified with
radiography. Despite urging by their parents, children with a true structural
problem like Scheuermann disease cannot stand straight. As a result of the
exaggerated thoracic kyphosis and lumbar lordosis, affected children typically
stand slumped, with the arms folded across a prominent abdomen. The kyphosis is
relatively inflexible, is not fully corrected when the patient attempts
thoracic hyperextension in the prone position, and is accentuated by forward
bending. Mild scoliosis is an associated finding in 20% to 30% of patients, and
contracture of the hamstring and pectoral muscles, which leads to forward
protrusion of the shoulder girdle, is common. Neurologic examination, usually
normal, may reveal a more serious condition such as kyphosis secondary to
congenital vertebral deformity or trauma.
Scheuermann disease is often misdiagnosed as postural round-back
deformity, which also occurs in pre- adolescent children. However, this type of
kyphosis is supple (i.e., it is corrected with prone hyperextension) and is not
accompanied by muscle contractures, wedging of the vertebral bodies, or
irregularities of the epiphyseal plates. Differential diagnosis includes
infectious spondylitis, hypoparathyroidism and hyperparathyroidism, rickets,
osteogenesis imperfecta, idiopathic juvenile osteoporosis, neurofibromatosis,
tumors, Morquio and Hurler syndromes, and traumatic injuries.
Treatment. In growing children, treatment is
instituted to arrest progression of the deformity, improve the cosmetic
appearance of the back, and alleviate any pain. The deformity has been shown in
some cases to be correctable as long as there is potential for further
vertebral growth and the kyphotic deformity is flexible. The spine is held in a
corrected position with a cast (not well
tolerated) or a high thoracic brace. The kyphosis can correct to a normal
curvature in the first year as evidenced by reconstruction of the wedged
vertebral bodies and anterior portion of the vertebral apophysis. If untreated,
the deformity may progress to a large degree and require surgical correction.
Many kyphotic deformities are recognized when the patient is older and less
flexible. Although individuals vary, the indications for surgery usually begin
with curves in excess of 60 degrees.
