Introduction:  Degenerative lumbar spondylolisthesis (DLS) is a debilitating condition associated with poor preoperative functional status. Surgical intervention has been shown to improve outcomes in this population though the nature of the most appropriate surgical intervention is controversial. The importance of maintaining and/or improving sagittal and pelvic spinal balance parameters has faced increasing emphasis in the DLS surgical population. However, little is known about the radiographic parameters most associated with improved functional outcomes among patients undergoing surgery for DLS. Thus, the objective of this study was to identify the radiographic parameters that correlate with functional outcomes after DLS surgery.  

Methods:  Retrospective analysis of the prospectively collected cohort of consecutively enrolled patients in the Canadian Spine Outcomes and Research Network (CSORN) database was performed. All enrolled study patients had a DLS diagnosis and underwent decompression in isolation or with posterolateral or interbody fusion. Patients reported their baseline and one-year post-operative leg and back pain on a 10-point logarithmic scale of severity in addition to completing the Oswestry Disability Index (ODI). Furthermore, multiple global and regional alignment parameters were documented at baseline and one-year postoperative including sagittal vertical axis (SVA), pelvic incidence (PI) and lumbar lordosis (LL). 

Results:  Two-hundred forty-one patients were available for analysis. Among participants, the mean age was 66 with 63% (152/241) female and a primary surgical indication of neurogenic claudication in 188/241 (78%) of patients. By Pearson correlation coefficient, worsened PI-LL mismatch >9cm was correlated with increased one-year postoperative ODI (.134, p=0.05), leg pain (.143, p=0.05) and back pain (0.189, p=0.01). A multiple linear regression was performed adjusting for baseline patient age, BMI, gender and preoperative presence of depression. From this regression analysis, worsening of a PI-LL mismatch was associated with a higher one-year postoperative ODI score R² 0.179 (95% CI 0.080, 0.415, p=0.004), back pain R² 0.152 (95% CI 0.021, 0.070, p <0.001) and leg pain R² 0.059 (95% CI 0.008, 0.066, p=0.014) score. Likewise, reduction of LL was associated with a higher ODI score R² 0.168 (-0.387, -0.024, p=0.027) and back pain R² 0.135 (95% CI -0.064, -0.010, p=0.007). Interestingly, worsened SVA >5cm was not statistically significant for worse one-year post-operative ODI, leg pain nor back pain scores.

Discussion:  In our longitudinal multi-centre cohort study worsening of sagittal balance and loss of lumbar lordosis with lumbar degenerative spondylolisthesis correlates with worse postoperative outcomes. Accordingly, preoperative emphasis on regional and global spinal alignment parameters must be considered in order to optimize surgical procedure indication and functional outcome in lumbar degenerative spondylolisthesis treatment.