Does change in focal lordosis after spinal fusion affect clinical outcomes in degenerative spondylolisthesis?

Study Design:Retrospective cohort study. Objective:The objective of this study is to determine the effect of focal lordosis and global alignment and proportion (GAP) scores on patient reported outcome measures (PROMs) after posterior lumbar fusion for patients with 1- or 2-level lumbar degenerative spondylolisthesis (DS). Summary of Background Data:In patients with DS, improvements in spinopelvic parameters are believed to improve clinical outcomes. However, the effect of changing focal lordosis in patients with 1-or 2-level degenerative lumbar spondylolisthesis is unclear. Materials and Methods:Postoperative spinopelvic parameters and perioperative focal lordosis changes were measured for 162 patients at a single academic center from January 2013 to December 2017. Patients were divided into three groups: >2° (lordotic group), between 2° and -2° (neutral group), and -2°° (kyphotic group). Patients were then reclassified based on GAP scores. Recovery ratios (RR) and the number of patients achieving the minimal clinically important difference (MCID) were calculated for PROMs. Standard descriptive statistics were reported for patient demographics and outcomes data. Multiple linear regression analysis controlled for confounders. Alpha was set at P < 0.05. Results:There was no significant association between change in focal lordosis and surgical complications including adjacent segment disease (P = 0.282), instrumentation failure (P = 0.196), pseudarthrosis (P = 0.623), or revision surgery (P = 0.424). In addition, the only PROM affected by change in focal lordosis was Mental Component Scores (ΔMCS-12) (lordotic = 2.5, neutral = 8.54, and kyphotic = 5.96, P = 0.017) and RR for MCS-12 (lordotic = 0.02, neutral = 0.14, kyphotic 0.10, P = 0.008). Linear regression analysis demonstrated focal lordosis was a predictor of decreased improvement in MCS-12 (β = -6.45 [-11.03- -1.83], P = 0.007). GAP scores suggested patients who were correctly proportioned had worse MCID compared to moderately disproportioned and severely disproportioned patients (P = 0.024). Conclusions:The change in focal lordosis not a significant predictor of change in PROMs for disability, pain, or physical function. Proportioned patients based on the GAP score had worse MCID for Oswestry Disability Index. Level of Evidence:III.