Dual Rod Posterior Instrumentation Without Fusion for the Treatment of Progressive Early Onset Scoliosis: A Multicenter Study

• (b, d - DePuy Acromed Corporation)

Purpose: The previous methods of posterior subcutaneous and submuscular instrumentation without fusion, to control the progressive curves in very young children have shown variable results and a high rate of complications. These techniques, however, have utilized only a single rod. This multicenter study was initiated to evaluate the efficacy and safety of a dual rod technique in achieving and maintaining correction while allowing additional spinal growth.

Methods: Thirty-eight patients with progressive early onset scoliosis who had primary dual rod constructs utilizing special connectors for periodic lengthening were reviewed. Twenty-three patients had a minimum of 2 years follow-up and qualified for this study. All procedures were primary; no revisions were included. There were 6 patients with infantile idiopathic scoliosis, 2 juvenile idiopathic, 3 congenital, 2 neuromuscular and 10 with other etiologies. All had previous unsuccessful bracing or casting. The mean age at surgery was 5+7 years. One patient had an annulotomy in addition to posterior instrumentation. Average number of lengthenings was 6. Follow-up averaged 4 1/2 years (range from 24 to 111 months).

Results: The mean scoliosis Cobb angle improved from 81 degrees to 38 degrees post-op and 40 degrees at latest follow-up. Kyphosis was 55 degrees pre-op, 36 degrees post-op and 47 degrees at follow-up. T1-S1 length increased from 23.3 cm to 28.6 cm after first surgery (elongation) and to 32.3 cm at follow-up. In addition to initial elongation averaging 5.3 cm, the length increase over the follow-up period was an average of 0.82 cm per year.Seven patients had their final definitive fusion. For these patients a total length of 14 cm was achieved from pre-op to final fusion(1 cm per year after first surgery). Complications included one hook dislodgement, one rod breakage, 2 contaminated wounds (superficial) and 1 patient required extension of instrumentation to one level below. No significant crank shaft phenomenon was noted.

Conclusion: This is the first report of patients treated surgically with dual rod instrumentation without fusion with a minimum of 2 years follow-up. The authors believe that the dual rod technique is safe and effective, provides superior stability comparing to single rod techniques, reduces complications and allows continued spinal growth in this challenging patient population.

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