Axial rotation predicts coronal correction in vertebral body tethering: a retrospective three-dimensional study in Hong Kong.

Abstract

Single-center retrospective study. By utilizing three-dimensional (3D) reconstruction models, our study aimed to investigate the three-dimensional changes in vertebral body tethering (VBT) and assess the relationship between axial-plane parameters and postoperative outcomes. Previous studies mainly focused on coronal plane correction but lacked investigation on axial plane changes following VBT. We included consecutive patients who underwent VBT in our institution (Queen Mary Hospital and Duchess of Kent Children's Hospital, Hong Kong) from February 2019 to April 2024. We used EOS radiographs to generate 3D reconstruction models, and parameters were analyzed preoperatively, immediately postoperatively, 1 year postoperatively, and 2 years postoperatively. The primary outcomes were changes in coronal, axial, and sagittal profiles at different time points. Secondary outcomes included the relationship between axial parameters with short-to-medium term changes in coronal/sagittal profiles. We included 44 patients (seven males, 37 females) with 58 instrumented curves, with an average follow-up of 36.3±17.1 months. The mean Cobb angle, apical vertebral rotation (AVR), and maximal vertebral rotation (MVR) improved from 48.0°±10.7°, 9.1°±5.7°, and 13.4°±5.7° preoperatively to 22.3°±8.9°, 6.2°±4.8°, and 9.8°±4.3° postoperatively, respectively, with correction maintained at 2 years. Preoperative AVR, MVR, and intraoperative derotation were significantly correlated with 1-year and 2-year correction rate and curve regression (Pearson correlation coefficient [r ]=0.35-0.63; p <0.001). Multivariate analysis confirmed AVR derotation and preoperative MVR as significant predictors for the 1-year correction rate. Tether breakage occurred in 27.6% (16/58) of patients. VBT was effective in correcting coronal and axial deformity at 2 years, but most correction occurred intraoperatively. Axial parameters were predictive for postoperative outcomes, with increased preoperative rotation associated with greater coronal correction. More aggressive derotation corresponded to greater correction. To improve surgical outcomes, clinicians should aim to achieve adequate correction by screw positioning and appropriate tensioning.