[Risk factors analysis of coronal imbalance after posterior long-level fixation and transforaminal lumbar interbody fusion for degenerative lumbar scoliosis].

OBJECTIVE: To explore the risk factors of coronal imbalance after posterior long-level fixation and fusion for degenerative lumbar scoliosis. METHODS: Retrospectivly analyzed the clinical records of 41 patients with degenerative lumbar scoliosis who had received posterior long-level fixation and fusion with selective transforaminal lumbar interbody fusion (TLIF) accompanied by Ponte osteotomy between August 2011 and July 2016. Patients were divided into imbalance group (group A, 11 cases) and balance group (group B, 30 cases) according to state of coronal imbalance measured at last follow-up. The radiographic parameters at preoperation and last follow-up were measured, and the variance of preoperative and last follow-up parameters were calculated. The radiographic parameters included coronal Cobb angle, coronal balance distance (CBD), apical vertebral translation (AVT), apical vertebral rotation (AVR), Cobb angle of lumbar sacral curve (LSC), and L 5 tilt angle (L 5TA). Univariate analysis was performed for the factors including gender, age, preoperative T value of bone mineral density, number of instrumented vertebra, upper and lower instrumented vertebra, segments of TLIF, decompression, and Ponte osteotomy, as well as the continuous variables of preoperative imaging parameters with significant difference were converted into two-category variables, obtained the influence factors of postoperative coronal imbalance. Multivariate logistic regression analysis was performed to verify the risk factors from the preliminary screened influence factors and the variance of imaging parameters with significant difference between the two groups. RESULTS: The follow-up time of groups A and B was (3.76±1.02) years and (3.56±1.03) years respectively, there was no significant difference between the two groups ( t=0.547, P=0.587). The coronal Cobb angle, AVT, LSC Cobb angle, and L 5TA in group A were significantly higher than those in group B before operation ( P<0.05), and all the imaging parameters in group A were significantly higher than those in group B at last follow-up ( P<0.05). There was no significant difference between the two groups in parameters including the variance of coronal Cobb angle, AVT, and LSC Cobb angle before and after operation ( P>0.05), and there were significant differences between the two groups in parameters including the variance of CBD, L 5TA, and AVR ( P<0.05). Univariate analysis showed that preoperative L 5TA was the influencing factor of postoperative coronal imbalance ( P<0.05). Multivariate logistic regression analysis showed that preoperative L 5TA≥15° was an independent risk factor of postoperative coronal imbalance, and variance of pre- and post-operative AVR was a protective factor. CONCLUSION: Preoperative L 5TA≥15° is an independent risk factor for coronal imbalance in patients with degenerative lumbar scoliosis after posterior long-level fixation and fusion.