Anterior release is not needed to restore kyphosis in moderate AIS with hypokyphosis.

Abstract

The purpose of this study is to evaluate if AR offers improved 3D kyphosis restoration during PSF for hypokyphosis in moderate AIS (< 70° coronal cobb), where the decision for AR is likely driven by sagittal concerns. A multicenter pediatric spine registry was queried for hypokyphotic (< 10°) Lenke 1-4 AIS patients aged < 20 years with > 2-year surgical follow-up. Coronal curves were limited to < 70°. A linear mixed model was created to predict 2-year 3D kyphosis by treatment and pre-op 3D kyphosis, while controlling for age, sex, thoracic coronal deformity and flexibility, osteotomy use, implant characteristics, surgery recency, and surgeon. 1384 patients were included with 53 (3.8%) undergoing PSF + AR. Mean preop 3D kyphosis was similar between PSF and PSF + AR groups (- 3.7° vs. - 0.5°; p = 0.08). PSF-AR had similar 2-year 3D kyphosis (23.0° [95% CI 20.5-25.4°] vs. 23.3° [22.9-23.6°]) and correction (26.7° [23.3-29.9°] vs. 23.7° [23.3-24.2°]) compared to PSF. When controlling for covariates, the models demonstrated no difference between approach (p = 0.058) or interaction of approach and preop 3D kyphosis (p = 0.31). Post-hoc power analysis showed an adequate sample size to detect a difference of 5° between approaches. PSF + AR had longer surgical times (324 vs. 266 min, p < 0.001) though no significant increase in overall complications (17% vs. 12.4%) compared to PSF alone. In AIS patients with coronal curve < 70° and 3D hypokyphosis of 10 to - 40°, treatment with PSF + AR did not improve 2-year sagittal correction more than PSF alone. Surgeon identity and surgery recency influenced post-operative kyphosis more than any other patient or surgical factor.