Distraction-Based Surgeries Increase Thoracic Sagittal Spine Length After 10 Lengthening Surgeries for Patients With Idiopathic Early-Onset Scoliosis

Study Design: Retrospective, comparative, multicenter. Objectives: To determine if the choice of proximal anchor affects thoracic sagittal spine length (SSL) for children with idiopathic early-onset scoliosis (EOS). Summary of Background Data: Debate exists as to whether spine growth is maintained during treatment for EOS. As rib- (RB) and spine-based (SB) distraction procedures may be kyphogenic, the traditional measurement of spine growth on coronal radiographs may not identify out-of-plane increases in spine length. A measure of SSL, along the spine's sagittal arc of curvature, has been validated to reliably assess the length of the thoracic spine. Methods: Patients with idiopathic EOS treated with distraction-based systems (minimum five-year follow-up, five lengthening surgeries) with radiographic analysis preoperatively, postimplant (L1), and during lengthening periods (L2–L5, L6–L10) were evaluated with primary outcome of T1–T12 SSL. Results: We identified 34 patients (14 RB, 20 SB) with preoperative age 4.9 years (4.2 RB vs. 5.4 SB), scoliosis 72° (60° RB vs. 77° SB; p<.05), kyphosis 39° (50° RB vs. 34° SB; p<.05), and SSL 17.8 cm (15.5 RB vs. 18.5 SB; p<.05). After initial scoliosis correction from implantation, scoliosis remained constant over time. RB patients had greater kyphosis than SB patients: L1, 46° RB vs. 19° SB (p<.05); L2–L5, 50° RB vs. 27° SB (p<.05); L6–L10, 56° RB vs. 26° SB (p<.05). SSL increased for both groups from preoperative to the 10th lengthening (p<.05). As compared with RB patients, SB patients had higher SSL preoperatively and maintained this difference to the 10th lengthening (p<.05). After 10 lengthening surgeries, when normalized to preoperative SSL, relative thoracic growth was greater for RB (27%) than for SB patients (19%) (p<.05). Conclusion: Regardless of proximal anchor choice, thoracic length continued to increase during the distraction phase of treatment for idiopathic EOS. Level of Evidence: Level III.