DOS 2019

188 · DOS Abstracts Distraction-to-stall versus estimated distraction in Magnetically Controlled Growing Rods Casper Dragsted, Sidsel Fruergaard, Mohit Jain, Deveza Deveza, John Heydemann, Søren Ohrt-Nissen, Thomas Andersen, Martin Gehrchen, Benny Dahl, Texas Children’s Hospital Spine Study Group Spine Unit, Department of Orthopaedic Surgery, Rigshospitalet; Department of Orthopedics and Scoliosis Surgery, Texas Children’s Hospital, TX, USA Background: Consensus is lacking regarding distraction frequency, amount and technique in the treatment of early-onset scoliosis (EOS) with magnetically controlled growing rods (MCGR). Purpose / Aim of Study: Compare distraction-to-stall with estimated dis- traction in the treatment with MCGR. Materials and Methods: We performed a two-center retrospective study of all children treated with MCGR from November 2013 to January 2019, hav- ing minimum one-year follow-up and undergoing minimum three distractions. Exclusion criteria were single-rod constructs and conversion cases. At one cen- ter (21 patients) we used a distraction- to-stall principle, and at the second center (18 patients) we used an estimated distraction amount principle. In dis- traction- to-stall, each rod was lengthened until the internal magnetic driver stopped (“clunking“) or the patient felt discomfort. In estimated distraction, a set distraction length was entered on the remote control before distraction. Both centers aimed for maximal distraction and curve correction at index sur- gery. Achieved lengthening was measured on radiographs and compared be- tween the two centers using a linear mixed effects model adjusted for number of instrumented levels. Findings / Results: Mean age at surgery was 9.5±2.0 years and 21 (55%) pa- tients were females. Etiology of the deformity was congenital/structural (n=7), neuromuscular (n=9), syndromic (n=3) or idiopathic (n=20). Age, sex, etiology and pre- and postoperative spinal height (T1-T12 and T1-S1) did not differ be- tween centers (p>0.46). Time between distractions were mean 17 days (95% CI 10-24) shorter in the distraction-to-stall compared with the estimated dis- traction group. Mechanical complications occurred in 10/39 patients, five at each center. In the linear mixed effects model, we found that achieved length- ening increased with number of instrumented levels; however, there was no significant difference between the two centers. Conclusions: In two comparable and consecutive cohorts we found no differ- ence in achieved lengthening between distraction-to-stall and estimated dis- traction lengthening principles. 144.