Postoperative Change of Thoracic Kyphosis after Corrective Surgery for Adult Spinal Deformity

INTRODUCTION: Correction of lumbar lordosis is the primary goal of surgical treatment of adult spinal deformity. However, only limited research has evaluated the effects of this correction on the adaptive curvature of the thoracic spine. The purpose of this study is to evaluate the change in thoracic curvature after corrective surgery to restore lumbar lordosis in patients with adult spinal deformity. METHODS: We completed a retrospective analysis of the radiological data of 65 patients, ≥50 years old, who underwent corrective surgery of lumbar spine lordosis from any level below T8 to the ilium. Patients with insufficient correction, defined by a pelvic incidence minus lumbar lordosis angle (PI-LL) > 10°, were excluded, with the data of 43 patients included in the analysis. The following radiological measures of spinal alignment were measured at three time points, preoperatively, on the first day of standing postoperatively and at 2 years post-surgery: sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), and PI-LL. RESULTS: Postoperative change in TK was correlated to preoperative TK and age. The increase in TK was larger for patients <75 years of age, increasing from 23.1° to 38.0° after surgery and to 46.7° at 2-years postoperatively. In contrast, for patients >75 years, TK remained largely unchanged at 37.8° just after surgery but increased substantively to 50.1° at the 2-year follow-up. The postoperative change in TK immediately after surgery was determined using equation “predict change in TK = −0.21 × age − 0.6 × preoperative TK + 41.8” by multiple regression analysis. CONCLUSIONS: Reciprocal change in TK after lumbar spine correction is correlated to preoperative TK and age.