Posterior-only unit rod instrumentation and fusion for neuromuscular scoliosis.

STUDY DESIGN: A retrospective study to determine the efficacy of posterior-only unit rod instrumentation and fusion in a skeletally immature neuromuscular scoliosis population.

OBJECTIVE: To determine whether the posterior-only approach to this population adequately addresses the concerns of correction of scoliosis and pelvic obliquity, maintenance of that correction over time, and the incidence of crankshaft phenomenon.

SUMMARY OF BACKGROUND DATA: Controversy exists regarding the need for anterior release to improve curve flexibility and the need to obtain an anterior arthrodesis in those skeletally immature patients at risk for crankshafting with continued anterior growth.

METHODS: From 1992 through 1997, 28 consecutive skeletally immature patients with neuromuscular scoliosis underwent posterior-only unit rod instrumentation and fusion for the treatment of progressive, symptomatic spinal deformities. Preoperative, immediate postoperative, and final follow-up radiographs were analyzed with respect to scoliosis and pelvic obliquity correction, maintenance of that correction over time, and the development of the crankshaft phenomenon as evidenced by loss of correction and/or increased rib-vertebral angle difference. The average age of the patients was 12.8 years and the average follow-up was 58 months with a minimum of 2 years.

RESULTS: Twenty-six patients were available for final follow-up. The initial Cobb angle correction averaged 66%, with 75% of the pelvic obliquity corrected. These corrections were maintained over time. Before surgery 27 of 28 patients were Risser 0, 1, or 2. The triradiate cartilage was open in nine patients, and five patients were < or =10 years of age. At the final follow-up 22 of the 26 patients were Risser 5 and 4 were Risser 4. There was one patient with increased rib-vertebral angle difference over the length of follow-up, with no loss of frontal or sagittal plane alignment.

CONCLUSIONS: These results indicate that even in the very young neuromuscular patient, acceptable amounts of curve correction can be achieved and maintained with posterior-only unit rod instrumentation and fusion. The biomechanical stiffness of this construct seemed to be able to prevent the crankshaft phenomenon in the majority of those patients at risk.