Distraction-based surgeries increase thoracic sagittal spine length after ten 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). 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 increase 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 5-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 degrees (60 degrees RB vs. 77 degrees SB; p < 0.05), kyphosis 39 degrees (50 degrees RB vs. 34 degrees SB; p < 0.05), and SSL 17.8 cm (15.5 RB vs. 18.5 SB; p < 0.05). After initial scoliosis correction from implantation, scoliosis remained constant over time. RB patients had greater kyphosis than SB patients: L1, 46 degrees RB vs. 19 degrees SB (p < 0.05); L2-L5, 50 degrees RB vs. 27 degrees SB (p < 0.05); L6-L10, 56 degrees RB vs. 26 degrees SB (p < 0.05). SSL increased for both groups from preoperative to the tenth lengthening (p < 0.05). As compared with RB patients, SB patients had higher SSL preoperatively and maintained this difference to the tenth lengthening (p < 0.05). After ten lengthening surgeries, when normalized to preoperative SSL, relative thoracic growth was greater for RB (27%) than for SB patients (19%) (p < 0.05). 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.