Risk Factors for Immediate Postoperative Coronal Imbalance in Degenerative Lumbar Scoliosis Patients Fused to Pelvis

STUDY DESIGN: Retrospective case-control radiographic study. OBJECTIVE: To identify risk factors for immediate postoperative coronal imbalance in degenerative lumbar scoliosis (DLS) patients fused to pelvis. METHODS: A total of 71 DLS patients treated with deformity correction surgery were reviewed. Measurements included coronal parameters such as global coronal malalignment (GCM), major Cobb angle, L4/L5 coronal tilt and sagittal parameters. Based on the orientation of L4 coronal tilt relative to C7 plumb line (PL) preoperatively, coronal patterns were subdivided into (1) consistency pattern, L4 coronally tilts toward C7 PL, and (2) opposition pattern, L4 coronally tilts opposite C7 PL; the proportion of these 2 patterns was analyzed. Also, the proportion of type C and surgical factors were recorded. According to postoperative GCM, patients were divided into imbalanced group and balanced group. RESULTS: Compared with the balanced group, the imbalanced group had a larger proportion of preoperative consistency pattern (79.17% vs 40.43%, P = .002), larger proportion of type C (29.17% vs 8.51%, P = .023), and lower amount of GCM correction (−4.92 ± 24.25 vs 14.52 ± 19.49 mm, P < .001). There were no significant intergroup differences regarding preoperative and postoperative major Cobb angle, preoperative and postoperative L4 or L5 coronal tilt, major Cobb correction, the amounts of correction of coronal tilt of L4/L5, osteotomy levels, osteotomy grades, instrumented levels, levels of interbody fusion, and distribution of upper instrumented vertebra. CONCLUSIONS: In addition to known risk factors such as type C, preoperative coronal consistency pattern might be a new risk factor for postoperative coronal imbalance in DLS patients fused to pelvis.