Coronal Imbalance After Three-Column Osteotomy in Thoracolumbar Congenital Kyphoscoliosis: Incidence and Risk Factors

STUDY DESIGN: Retrospective radiographical clinical study. OBJECTIVE: To investigate the incidence and risk factors of coronal imbalance (CI) after three-column osteotomy (3-CO) in patients with thoracolumbar congenital kyphoscoliosis (CKS). SUMMARY OF BACKGROUND DATA: The incidence and risk factors of postoperative CI have been reported in adolescent idiopathic and degenerative lumbar scoliosis. However, limited data exists for patients with CKS after 3-CO. METHODS: We reviewed a consecutive series of patients with CKS who underwent posterior-only 3-CO. Coronal curve patterns were classified according to absolute C7 translation values into: Type A, C7 translation is less than 30 mm; Type B, C7 translation more than or equal to 30 mm and C7 plumb line (C7PL) shifted to the concave side of the main curve; and Type C, C7 translation more than or equal to 30 mm and C7PL shifted to the convex side. CI was defined as C7 translation on either side more than or equal to 30 mm. According to C7 translation at the latest follow-up, patients was subdivided into an imbalanced group and a balanced group. RESULTS: One-hundred-thirty patients (mean age, 17.7 ± 5.2 yr) were recruited. The mean follow-up was 41.3 ± 18.5 months. Twenty-six patients (20%) were identified as having CI at the latest follow-up. Compared with the balanced group, the imbalanced group had a larger proportion of preoperative Type C pattern, higher main curve correction, and greater lowest instrumented vertebra (LIV) tilt before and after surgery. Multiple logistic regression showed that risk factors for CI were preoperative type C pattern, preoperative LIV tilt more than or equal to 23.5° and immediate postoperative LIV tilt more than or equal to 12.3°. CONCLUSION: The incidence of CI in patients with CKS after 3-CO was 20%. A preoperative type C pattern, preoperative LIV tilt more than or equal to 23.5°, and immediate postoperative LIV tilt more than or equal to 12.3° were found to be associated with CI at the latest follow-up. LEVEL OF EVIDENCE: 3.