Parallel Proximal Fixation in Rib-Based Growing Rod System A Novel Approach to Deal With Proximal Anchor Migration John Heflin, MD,  Michelle Welborn, MD, y Norman Ramirez-Lluch, MD, z Ivan Iriarte, MD, z Ron El-Hawary, MD, § Graham T. Fedorak, MD,  and John T. Smith, MD  , Children’s Spine Study Group { 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. Differ- ences 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 ¼ 0.001). Controlling for the different lengths of follow- up in the two groups there was a significantly higher rate of implant failure (P ¼ 0.043) and requirement for nonroutine surgical intervention (P ¼ 0.029) in the in-line group. There was a trend toward increased complications in the in-line group (P ¼ 0.058). Conclusion. Failure of proximal fixation is the most common complication in management of EOS with rib-based distrac- tion. 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. Key words: complications, early-onset scoliosis, migration, parallel proximal fixation, proximal hook, rib-based growing rod, surgery. Level of Evidence: 3 Spine 2018;43:E855–E858 R ib-based distraction is frequently used in the man- agement of progressive early-onset scoliosis (EOS) as an alternative to spine-based growth friendly systems . 1–7 Both spine-based and rib-based distraction have been shown to be effective in managing spinal deformity and improving space available for the lungs. 1–11 However, with the use of VEPTR (Depuy-Synthes Raynham, MA) and other rib based distraction systems, proximal anchor failure continues to be a significant problem. 2,12–15 Rates of failure of proximal fixation with VEPTR range between 19% and 53% per patient, with higher rates in series with longer follow-up. 2,4,10,13–15 Proximal fixation failure when rib- based distraction is used continues to be problematic for recently developed devices. A parallel proximal anchor construct, utilizing transverse connectors, has been adopted by many surgeons in an effort to decrease proximal anchor failure. This configuration allows independent preloading of the rib-cradle on the ribs, ensuring that each point of fixation makes direct contact with the intended rib. Theoretically, by dispersing contact forces more evenly across multiple ribs the distraction forces at each bone-implant interface are decreased. Although it seems reasonable to think this approach could result in From the  University of Utah, Salt Lake City, UT; y Shriner’s Hospital for Children Portland, Portland, OR; z Hospital de la Concepcion, San German, Puerto Rico; § IWK Health Centre, Halifax, Nova Scotia, Canada; and { Children’s Spine Foundation, Valley Forge, PA. Acknowledgment date: July 10, 2017. First revision date: October 11, 2017. Acceptance date: December 6, 2017. The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication. No funds were received in support of this work. Relevant financial activities outside the submitted work: board membership, consultancy, grants, royalties. Address correspondence and reprint requests to John T. Smith, MD, Uni- versity of Utah, 100 North Mario Capecchi Dr, Suite 4550, Salt Lake City, UT 84113; E-mail: John.Smith@hsc.utah.edu DOI: 10.1097/BRS.0000000000002527 Spine www.spinejournal.com E855 SPINE Volume 43, Number 14, pp E855–E858 ß 2018 Wolters Kluwer Health, Inc. All rights reserved. SURGERY Copyright © 2018 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.