Loss of lumbar lordosis. A complication of spinal fusion for scoliosis.

Symptomatic loss of lumbar lordosis is a disabling complication of scoliosis surgery. This so-called "flat-back syndrome" is characterized by an inability to stand erect and by upper back pain. Distraction instrumentation extending into the lower lumbar spine or sacrum is the most frequently identified etiologic factor responsible for loss of lordosis. The more distal the level of instrumentation, the severer the loss of lumbar lordosis. Other factors that may aggravate the loss of lordosis include thoracolumbar kyphosis, fixed thoracic kyphosis, hip flexion contractures, and pseudoarthrosis. Because of the wide range of values for kyphosis and lordosis in normal individuals, there is no absolute value that can be considered "normal." It is the overall sagittal plane balance that is most important. The most useful radiographic measurement to evaluate this sagittal plane balance is the full-length standing lateral radiograph with the knees extended. On this view, the C7-S1 measurement should fall within 2 cm of the anterior aspect of the sacrum. Surgical treatment for symptomatic loss of lumbar lordosis consists of closing wedge osteotomies through the fusion mass. This should generally be preceded by an anterior release and interbody fusion. Correction should be obtained at the site of the deformity with particular attention paid to the thoracolumbar junction. The surgery is difficult and the risk of complication is high. The most important aspect of this postural disorder is prevention. Avoid distraction instrumentation that extends into the lumbar spine if possible. When distraction instrumentation is used, the techniques described will help preserve lumbar lordosis. When performing a fusion to the sacrum, distraction instrumentation should not be used.