Matched comparison of non-fusion surgeries for adolescent idiopathic scoliosis: posterior dynamic distraction device and vertebral body tethering.

Purpose: Two non-fusion devices for adolescent idiopathic scoliosis (AIS) received HDE approval for clinical use in 2019: posterior dynamic distraction device (PDDD) and vertebral body tethering system (VBT). Although indications are similar, there is no comparative study of these devices. We hypothesize that curve correction will be comparable, but PDDD will have better perioperative metrics.

Methods: AIS PDDD patients were prospectively enrolled in this matched multicenter study. Inclusion criteria were Lenke 1 or 5 curves, preoperative curves 35°-60°, correction to ≤30° on bending radiographs, and kyphosis <55°. Patients were matched by age, sex, Risser, curve type and curve magnitude to a single-center cohort of VBT patients. Results were compared at 2 years.

Results: 20 PDDD patients were matched to 20 VBT patients. Blood loss was higher in the VBT cohort (88 vs. 36 ml, p < 0.001). Operative time and postoperative length of stay were longer in the VBT cohort, 177 vs. 115 min (p < 0.001) (2.9 vs. 1.2 days, p < 0.001). Postoperative curve measurement and correction at 6 months were better in the PDDD cohort (15° vs. 24°, p < 0.001; 68% vs. 50%, p < 0.001). At 1-year, PDDD patients had improved Cobb angles (14° vs. 21°, p = 0.001). At 2 years, a correction was improved in the PDDD cohort, with a curve measurement of 17° for PDDD and 22° for VBT (p = 0.043). At the latest follow-up, 3 PDDD patients and 1 VBT patient underwent revision surgery.

Conclusion: Early results show PDDD demonstrates better index correction, reduced operative time, less blood loss, and shorter length of stay but higher rates of revision compared to a matched cohort of VBT patients at two-year follow-up.

Level of evidence: Level II, prospective cohort matched comparative study.