The variability of response of scoliotic spines to segmental spinal instrumentation

Ninety-two patients (71 idiopathic, 15 neurogenic, 2 Marfan's syndrome, 1 Down's syndrome, 1 osteogenesis imperfecta, 1 Prader-Willi syndrome, 1 Klippel-Trenaunay-Weber syndrome), ages 9-49 years, had posterior spine fusion and stabilization with Luque L-rods and sublaminar segmental wires (SSI) for progressive scoliosis. There were no neurologic complications. The average preoperative major curve of 52 degrees (37-113 degrees) initially corrected to 30 degrees (6-94 degrees), and at last follow-up (range, 2-7 years), was 33 degrees (8-90 degrees). There was marked variability in curvature correction and maintenance of correction, with 14 patients progressively decreasing their curvatures postoperatively. Average preoperative Pedriolle vertebral rotation angle for all 92 patients was 16 degrees (4-26 degrees), which initially corrected to 14 degrees (0-24 degrees), and at last follow-up remained 14 degrees (0-23 degrees). Although SSI had little influence on rotation, 12 patients progressively decreased their rotational deformity after operation. Aside from the positive influence of curve flexibility on the degree of postoperative curve correction, the authors could not identify factors explaining how curvature and vertebral rotation responded so variably to SSI. The authors recommend continued use of SSI to stabilize curvatures in osteopenic patients (particularly those with neuromuscular disease), but rotational deformity will probably persist.