[Risk factors of coronal imbalance following posterior lumbar short-level fixation and fusion for degenerative lumbar scoliosis].

Abstract

Objective: To explore the risk factors associated with coronal imbalance following posterior short-level fixation and fusion surgery for patients with degenerative lumbar scoliosis (DLS). Methods: A retrospective analysis was conducted on the clinical data of patients who underwent posterior short-level fixation and fusion for the treatment of DLS at Shanghai Changzheng Hospital from January 2018 to December 2022. The postoperative follow-up period was 12 months. Based on the postoperative distance between the C₇ plumb line and the central sacral vertical line (C₇-CSVL), patients were divided into an imbalance group (C₇-CSVL ≥20 mm) and a balance group (C₇-CSVL <20 mm). Demographics, radiographic and surgical factors were compared between the two groups. The cutoff values for postoperative coronal imbalance in patients with ipsilateral and contralateral DLS were determined by analyzing the main curve sizes of the thoracolumbar spine, C₇-CSVL offset, apex vertebra offset, and lumbosacral base curve size using receiver operating characteristic (ROC) curves. A logistic regression model was performed to detect the risk factors for postoperative coronal imbalance following short-level fixation and fusion in patients with DLS. Results: A total of 234 patients [62 males, 172 females, with a mean age of (66.90±6.93) years] who underwent short-level fixation and fusion surgery for DLS were included in this study. Of these, 44 patients progressed postoperative coronal imbalance [12 males, 32 females, with an average age of (68.50±7.06) years], 190 patients did not endure postoperative coronal imbalance [50 males, 140 females, with a mean age of (66.54±6.86) years]. There were differences between the coronal balance group and the coronal imbalance group in preoperative C₇-CSVL [(1.63±1.36)cm vs (2.51±1.66)cm], lowest instrumented vertebra(LIV) tilt (4.84°±4.65° vs 6.81°±4.94°), LIV rotation [Nash-moe grade one, 32 cases (16.84%) vs 12 cases (28.57%)], Cobb-angle of the thoracolumbar main curve (19.15°±6.85° vs 26.74°±8.02°), Cobb-angle of the fractional curve (9.64°±5.27° vs 13.83°±5.01°), apical vertebral translation [(1.95±0.92) cm vs (3.11±0.96) cm], the rigidity of the thoracolumbar major curve [62 cases (32.6%) vs 24 cases (54.5%)] (all P<0.05). The categorical variables based on the ROC curve cut-off values [the thoracolumbar main curve pattern, the C₇-CSVL pattern, the apical vertebra translation (AVT) pattern, and the fractional curve pattern], as well as the correction pattern of key curve, showed differences between the two groups with all P<0.05; subsequently, all variables with P<0.05 were included in a forward multivariate logistic regression analysis, the results revealed that the higher thoracolumbar Cobb-angle pattern (OR=11.98, 95%CI: 3.680-39.000), the higher C₇-CSVL pattern (OR=6.603, 95%CI: 2.324-18.759), the higher AVT pattern (OR=4.362, 95%CI: 1.498-12.700), the higher fractional curve pattern (OR=3.756, 95%CI: 1.191-11.847), and the inferior correction pattern of key curve (OR=20.000, 95%CI: 6.211-66.667) were the risk factors associated with postoperative coronal imbalance after short-level fixation and fusion for the DLS. Conclusion: The higher thoracolumbar Cobb-angle pattern, the higher C₇-CSVL pattern, the higher AVT pattern, the higher fractional curve pattern and the inferior correction pattern of key curve were the risk factors associated with postoperative coronal imbalance after short-level fixation and fusion for the DLS.