The Longitudinal Effects of Posterior Spinal Fusion with Derotation on Axial Deformity in Adolescent Idiopathic Scoliosis

Study Design. Retrospective case series. Objective. To characterize the change in angle of trunk rotation (ATR), axial vertebral rotation (AVR), and body surface rotation (BSR) in patients with adolescent idiopathic scoliosis (AIS) undergoing posterior spinal fusion (PSF) with en-bloc derotation across multiple postoperative visits. Summary of Background Data. Previous research has documented ATR, AVR, and BSR correction for AIS patients after surgery. However, there is a lack of evidence on the sustainability of this correction over time. Methods. This was a retrospective study from a single-center prospective surface topographic registry of patients with AIS, age 11-20 at time of surgery, who underwent PSF with en-bloc derotation. Patients with previous spine surgery were excluded. ATR was measured with a scoliometer, AVR through EOS radiographic imaging, and BSR via surface topographic scanning, Data collection occurred at: preoperative, six-week, three-month, six-month, one-year, and two-year postoperative visits. BSR and AVR were tracked at the preoperative apical vertebral level, and the level with maximum deformity, at each respective timepoint. Generalized estimating equations models were used for statistical analysis. Covariates included age, sex, and body mass index. Results. 49 patients (73.4% female, mean age 14.6±2.2 years, mean preoperative coronal curve angle 57.9°±8.5, and 67% major thoracic) were evaluated. ATR correction was significantly improved at all postoperative timepoints and there was no significant loss of correction. AVR Max and AVR Apex were significantly improved at all timepoints but there was a significant loss of correction for AVR Apex between the six-week and one-year visit ( P =0.032). BSR Max achieved significant improvement at the three-month visit. BSR Apex was significantly improved at the three-month and one-year visit. Conclusion. ATR and AVR demonstrated significant axial plane correction at two-years postoperative in patients undergoing PSF for AIS. BSR did not maintain significant improvement by the two-year visit.