Scheuermann’s kyphosis is a rigid sagittal plane deformity within the thoracic, thoracolumbar, or lumbar spine. The cause of Scheuermann’s kyphosis (often named as “Scheuermann’s disease,” or simply “Scheuermann’s”) is not known, but is manifest by uneven growth of the vertebrae in the sagittal plane; additional posterior growth results in wedging of the vertebrae and a rounded, hunched back that does not fully correct with active extension. Approximately 50% of cases of Scheuermann's kyphosis as associated with back pain.
Structure and Function
Kyphosis refers to a convex curvature of the spine; the corresponding term, lordosis, refers to a concave curvature (see Figure 1). Normal thoracic kyphosis averages approximately 35 degrees with the cervical and lumbar spine both being lordotic.
Scheuermann’s kyphosis is an increased amount of kyphosis (>45 degrees) and is defined radiographically. (Because some kyphosis is normally present, technically speaking this condition should be called "Scheuermann’s hyperkyphosis".) The radiographic definition is a patient having three or more contiguous vertebrae with at least 5 degrees of anterior wedging. There are vertebral endplate abnormalities resulting in disc space narrowing that may be caused by an error in collagen aggregation. Schmorl’s nodes, which are disc herniations into the vertebral endplate, are present.
The true etiology of Scheuermann’s kyphosis is unknown but multiple theories exist. Scheuermann’s theory was that the growth disturbance is due to osteonecrosis of the vertebral ring apophysis. This causes a growth arrest in the anterior vertebral body and radiographically is depicted by wedging. Schmorl’s theory suggests disc material herniating through the vertebral end plate causes loss of height & ultimately the anterior wedging. Growth hormone abnormalities could possibly be a causative factor. Relative osteoporosis can lead to a compression deformity, thus causing the anterior vertebral wedging and increased kyphosis. There are possible genetic causes, as there is a high rate of heritability and an autosomal dominant inheritance pattern.
The most evident clinical manifestation of Scheuermann’s kyphosis comes with the physical exam. Patients will have increased kyphosis that is exacerbated with bending forward, (see Figure 2). The patients may also have compensatory hyperlordosis of the lumbar or cervical spine. This can lead to tightness in the hamstrings and iliopsoas muscles. Patients with more severe curves also have a higher incidence of back pain. Neurologic deficits, while rare, require a full neurologic exam.
After a patient’s physical exam is worrisome for Scheuermann’s kyphosis, an AP and lateral spine radiograph should be obtained (Figure 3).
On the AP radiograph, the presence or absence of scoliosis should be noted.
Scheuermann’s kyphosis is defined by a rigid thoracic hyperkyphosis greater than 45 degrees, associated with anterior wedging of three consecutive vertebrae measuring at least 5 degrees per vertebral body (Figure 4).
Disc space narrowing, endplate irregularities, and Schmorl’s nodes can be noted on the lateral radiograph. Endplate irregularities are more common in thoracolumbar and lumbar Scheuermann’s kyphosis compared to vertebral wedging.
Sagittal balance can be noted on the lateral radiograph by using the C7 plumb line and the posterior sacral vertical line.
The entire spine must be included on the x-ray as Scheuermann's kyphosis can extend all the way to the thoracolumbar regions. Thoracolumbar Scheuermann's is a far less common form, but is associated with increased back pain and more likely to be progressive.
A supine hyperextension lateral radiograph over a bolster may be obtained to differentiate Scheuermann’s kyphosis from postural kyphosis. As opposed to postural kyphosis, Scheuermann’s kyphosis is relatively inflexible on the hyperextension lateral radiograph.
MRI may be obtained at the discretion of the surgeon to identify disc herniations spinal stenosis or other spinal abnormalities. Any neurological deficit or symptom should be evaluated with an MRI.
Scheuermann’s kyphosis affects men and woman equally, with a prevalence between 0.4%-10%. Scheuermann’s kyphosis is the most common type of structural kyphosis in adolescents with a typical onset between the ages of 10-12. Thoracic Scheuermann’s kyphosis is by far the most common, which is classified as a curve apex between T6-T8. Males are approximately five times more commonly affected
The main differentiation that must be made is between Scheuermann’s kyphosis and postural kyphosis. Postural kyphosis will correct with extension, and radiographs will reveal the absence of anterior vertebral wedging.
Severe hyperkyphosis can be caused by vertebral compression fractures; this would be on the differential diagnosis for older females much more that in the pediatric or adolescent male population normally affected by Scheuermann’s.
Congenital kyphosis may be found if vertebrae are malformed or fused. A congenital kyphosis in the absence of neurological disorders is rare.
Nutritional kyphosis can result from rickets, usually due to a vitamin D deficiency.
If there is lower back pain, spondylolysis and spondylolisthesis must be ruled out.
Any neurologic deficit or complaint should be evaluated with a full physical examination, radiograph, and advanced imaging. Back pain along with constitutional symptoms should be investigated fully. Spinal deformity may happen in the setting of malignancy, therefore imaging should be thoroughly evaluated by a radiologist as well as the ordering physician.
Treatment Options and Outcomes
The treatment of mild to moderate (less than 50-80 degrees) Scheuermann’s kyphosis is non-operative. Non-operative treatment includes stretching and physical therapy with routine radiographic follow up. Therapy and exercises include postural improvement, thoracic extensor, and core strengthening.
Bracing with an extension orthosis has been attempted (Figure 5). Bracing requires significant patient compliance with brace wear of 16-23 hours per day. As is the case with scoliosis, bracing is chosen not so much to affect a correction but to stop progression; thus, it is indicated only if there is remaining skeletal growth anticipated.
Operative treatment should be considered only in severe curves. Other indications for surgery include progressive deformity, neurologic deficit, spinal cord compression, and severe pain. As opposed to idiopathic scoliosis, there is no agreement on Cobb angle where surgery should be recommended.
Surgery includes posterior instrumented spinal fusion with pedicle screw fixation (Figure 6). Anterior surgery is much less common with improvements in posterior surgical intervention. With severe, rigid curves posterior (Ponte) osteotomies may be performed. Anticipation of 5-10 degrees of correction with each posterior osteotomy performed. More aggressive osteotomies (pedicle subtraction or vertebral column resection) can be used with increased risk of complications. Intraoperative neuromonitoring is the standard of care in patients with spinal deformity.
Patient’s with curves less than 60 degrees typically have a benign course and a good clinical outcome with observation alone.
Patients with severe kyphosis of >100 degrees have negatively affected pulmonary function. There is evidence suggesting long term progression of deformity without correlation to negative effects on function in untreated patients with smaller curves.
The Scoliosis Research Society and Harms Study Group both reported an overall complications rate of approximately 15% in Scheuermann’s Kyphosis.
Neurologic complications with posterior spinal fusion have a reported rate of 0.6-0.8%, which is slightly higher than the rates in idiopathic scoliosis. There is conflicting evidence on whether combined anterior/posterior procedures have higher neuromonitoring changes compared to posterior only procedures.
Proximal and distal junctional kyphosis are complications that can be mitigated by selecting appropriate fusion levels, avoiding overcorrection >50% of original curve, construct choice, and correcting sagittal balance.
While the natural history of Scheuermann’s kyphosis tends to be benign, patients are more likely to pursue jobs that require less strenuous physical activity. Also, there is a cosmetic deformity. In all, there are important psychosocial considerations beyond the medical aspects of the condition.
Kyphosis, Schmorl’s node
Evaluate lateral x-rays of the spine and identify abnormal alignment.