Posterior osteotomy and instrumentation for thoracolumbar kyphosis in patients with achondroplasia

Study Design. A retrospective case series of surgically treated achondroplastic patients with severe thoracolumbar kyphosis. Objective. To evaluate the outcome of surgical treatment for thoracolumbar kyphosis in patients associated with achondroplasia presenting with paraparesis. Summary of Background Data. Thoracolumbar kyphosis is one of the frequent skeletal manifestations in patients with achondroplasia. Few papers have been published on the surgical treatment of this condition, especially in skeletally mature patients. Methods. Four patients with achondroplasia who developed neurologic deficit due to severe thoracolumbar kyphosis and underwent surgical treatment were evaluated (mean age, 32.5 years; mean follow-up, 3.0 years). Posterior osteotomy with segmental instrumentation was performed in all cases. The surgical procedures included pedicle subtraction osteotomy in 2 patients without a hypoplastic apical vertebra and spondylectomy with reconstruction of the anterior column in 2 patients with a hypoplastic apical vertebra. Neurologic outcomes (JOA scores), correction of kyphosis, and operative complications were assessed. Results. All patients had gait disturbance, and 2 patients were unambulatory before surgery. The average preoperative JOA score was 5.8 points, which was improved to 9.3 points at the final follow-up (mean recovery rate, 75%). All patients obtained neurologic improvement and became ambulatory either with or without crutches after surgery. The mean preoperative kyphotic angle was 96.3 (range, 57-117). The postoperative angles averaged 55.3 (range, 30-110), yielding a mean correction rate of 43.6%. Neither loss of correction nor pseudarthrosis has been observed during the follow-up period. Partial nerve root laceration and dural tear resulting in transient postoperative muscle weakness were observed in 2 patients as complications. Conclusions. Posterior spinal osteotomy with segmental instrumentation is a reasonable surgical option for thoracolumbar kyphosis in patients with achondroplasia. Modification of the surgical procedures depending on the presence or absence of the dysplastic changes of the apical vertebra is necessary to obtain optimal results.