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 neuromusc ular scoliosis population. Objective. To determine whether the posterior-only approach to this populat ion 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 anter ior release to improve curve flexibility and the need to obtain an anterior arthrodesis in those skeletally immature patients at risk for crankshaftin g with continued anterior growth. Methods. From 1992 through 1997, 28 consecutive skeletally immature patient s with neuromuscular scoliosis underwent posterior-only unit rod instrument ation and fusion for the treatment of progressive, symptomatic spinal defor mities. Preoperative, immediate postoperative, and final follow-up radiogra phs were analyzed with respect to scoliosis and pelvic obliquity correction , maintenance of that correction over time, and the development of the cran kshaft phenomenon as evidenced by loss of correction and/or increased rib-v ertebral angle difference. The average age of the patients was 12.8 years a nd the average follow-up was 58 months with a minimum of 2 years. Results. Twenty-six patients were available for final follow-up. The initia l Cobb angle correction averaged 66%, with 75% of the pelvic obliquity corr ected. These corrections were maintained overtime. Before surgery 27 of 28 patients were Risser 0, 1, or 2. The triradiate cartilage was open in nine patients, and five patients were less than or equal to 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 alignmen t. Conclusions. These results indicate that even in the very young neuromuscul ar patient, acceptable amounts of curve correction can be achieved and main tained with posterior-only unit rod instrumentation and fusion. The biomech anical stiffness of this construct seemed to be able to prevent the cranksh aft phenomenon in the majority of those patients at risk.