Spinal Fusion with Instrumentation for Progressive Thoracolumbar Kyphosis in Pediatric Achondroplasia

Kyphotic deformity of the thoracolumbar spine commonly occurs in the pediatric achondroplasia patient. Most curves will resolve when walking begins. However, surgical stabilization may be indicated for progressive deformity, neurologic compromise, or after laminectomy. The conventional approach of anterior and posterior fusion has achieved minimal correction, tended to avoid instrumentation, and had a high risk of neurological deterioration (1,2). To our knowledge, the literature contains only two achondroplasia patients who have had spinal fusion with pedicle screw instrumentation for kyphosis (1,3). We present a series of 11 pediatric patients with achondroplasia who were treated surgically for progressive kyphosis with instrumentation. The age at the time of surgery varied from 4 to 21 years (mean 12 years). The thoracolumbar kyphotic deformity ranged from 43 to 88 degrees (mean 64 degrees). Three patients had progressive kyphosis and were without neurological symptoms prior to surgery (mean curve of 56 degrees). Neurogenic claudication was present in eight (mean age of curve of 67 degrees), gait disturbance and weakness in three (mean curve of 53 degrees), bladder dysfunction in two (mean curve of 64 degrees), and bowel dysfunction in one (curve of 75 degrees). Four patients had had previous thoracolumbar laminectomies. The type of surgery preformed on these patients was variable. Of the 11 patients in the series, five patients had both anterior and posterior fusion and six had posterior fusion only. The median number of vertebrae fused anteriorly consisted of 5 and posteriorly of 7. The three patients with asymptomatic progressive kyphosis (mean age 6.5 years) had anterior vertebral body screws with instrumentation and posterior fusion followed five months later by a second procedure to ensure posterior bone graft fixation. The eight patients with symptomatic evidence of stenosis were treated with concomitant laminectomies, ranging from T9-T12 to L3-S1. Of these patients, one also had anterior release with posterior pedicle screw instrumentation, one had both anterior and posterior instrumentation, and six had posterior pedicle screw instrumentation only. Fusion was carried caudal to L4 in three of these patients. Bone graft consisted of allograft (seven patients), iliac crest autograft (seven patients) or rib autograft (four patients). The final measurements of thoracolumbar kyphosis ranged from 16 to 48 degrees (mean 31 degrees), representing a correction of 17 to 73 percent (mean 51 degrees). In nine patients, somatosensory evoked potentials remained intact throughout the procedure; a wake-up test confirmed neurological status in two others. Postoperative follow-up ranged from 24 to 58 months (mean 38 months). Two patients had instrumentation fracture secondary to trauma and one patient had a dural leak. There were no postoperative infections. At most recent follow-up, all 11 patients reported significant improvement in symptoms and neurologic function and all are healed based on radiographic studies. No patients have experienced progression of their kyphosis.In our experience, spinal fusion with vertebral body and/or pedicle screw fixation in the pediatric achondroplasia patient is a reliable technique that results in a solid fusion and good correction. Most importantly, instrumentation of the anchondroplasia spine did not precipitate any of the neuromonitoring difficulties or neurological losses that have been reported in previous studies.

(1) Tolo VT. Surgical treatment of kyphosis in achondroplasia. Basic Life Sci 1988;48:257-9.

(2) Lonstein JE. Treatment of kyphosis and lumbar stenosis in achondroplasia. Basic Life Sci 1988;48:283-92.

(3) Tolo VT, Kopits SE. Surgical treatment of thoracolumbar kyphosis in achondroplasia. Orthop Trans 1988;12:254-255.