Parallel Proximal Fixation in Rib-Based Growing Rod System: A Novel Approach to Deal With Proximal Anchor Migration.

STUDY DESIGN: Retrospective case control.

OBJECTIVE: To report on differences in implant failure rates and complications requiring reoperation in children with early-onset scoliosis (EOS) treated with rib-based distraction utilizing four proximal fixation points in either a parallel or in-line configuration.

SUMMARY OF BACKGROUND DATA: Proximal anchor failure continues to be a significant problem in growth-friendly surgery using rib-based distraction to treat children with EOS. Differences between parallel and in-line proximal anchor constructs have not been previously assessed.

METHODS: A multicenter registry was reviewed to identify children treated for EOS with rib-based distraction between 2011 and 2014 with a minimum of 2 years follow-up after implantation. Patients were divided into those with in-line and parallel proximal rib-cradle configurations, and only those with exactly four fixation points (two per side) were included. Charts were reviewed for demographic, clinical, and radiographic information.

RESULTS: A total of 56 patients were identified-31 with in-line constructs and 25 with parallel constructs. Follow-up in the in-line group was a mean of 4.06 years versus 3.16 in the parallel group (P = 0.001). Controlling for the different lengths of follow-up in the two groups there was a significantly higher rate of implant failure (P = 0.043) and requirement for nonroutine surgical intervention (P = 0.029) in the in-line group. There was a trend toward increased complications in the in-line group (P = 0.058).

CONCLUSION: Failure of proximal fixation is the most common complication in management of EOS with rib-based distraction. This study identifies that when the number of proximal fixation points are matched, parallel constructs result in lower rates of implant failure and need for unplanned reoperation than in-line constructs. Although this study was limited to patients in whom the VEPTR device was employed, these principles are likely applicable to other rib-based distraction devices used to treat EOS.

LEVEL OF EVIDENCE: 3.