What Factors Are Associated With Kyphosis Restoration in Lordotic Adolescent Idiopathic Scoliosis Patients?

Abstract

Study DesignReview of a prospective adolescent idiopathic scoliosis (AIS) multicenter registry. ObjectiveTo evaluate predictors of surgical thoracic kyphosis restoration in AIS patients with lordotic preoperative thoracic sagittal profiles. Summary of Background DataPrior work on kyphosis-producing techniques has yielded mixed findings and has focused on the sagittal plane in 2D. MethodsA validated formula to predict 3D T5–T12 sagittal alignment using standard 2D measures was applied in a cohort of 1614 Lenke 1-4 patients treated with posterior instrumentation using 5.5-mm-diameter rods. Patients with 3D kyphosis 1 standard deviation (12.2°) below the mean (5.3°) were identified as the study cohort. Predictors of 3D T5–T12 kyphosis at two years were evaluated using univariate analysis followed by Classification and Regression Tree (CART). ResultsThere were 134 patients identified. All had preoperative 3D T5–T12 kyphosis of <−7°. The average 3D kyphosis was −13° ± 5° preoperatively and 20° ± 7° at two years (p < .001). The thoracic coronal curve improved from 62° ± 12° to 21° ± 8° at two years (p < .001). Of 15 variables analyzed, multivariate CART analysis identified only surgeon as a predictor of 2-year kyphosis. Two surgeon groups were identified by CART which included those who restored more kyphosis versus those who restored less. Subsequent analysis demonstrated significant differences between groups in the rate of Ponte osteotomies used (p < .023), stainless steel versus cobalt chromium rods (p < .001), and segmental screw fixation (p < .001). ConclusionKyphosis restoration in patients with preoperative lordosis in the thoracic sagittal plane is possible. In this analysis, there was not one single technique identified as being solely responsible for the ability to restore kyphosis. The most predictive factor identified was the surgeon performing the correction, which is likely a reflection of focus on deformity correction in three planes, as well as a combination of methods used to restore kyphosis. Level of EvidenceLevel III, therapeutic.