How does spinopelvic alignment influence short-term clinical outcomes after lumbar fusion in patients with single-level degenerative spondylolisthesis?

CONTEXT: Studies on adult spinal deformity have shown spinopelvic malalignment results in worse outcomes. However, it is unclear if this relationship exists in patients with single-level degenerative spondylolisthesis (DS) receiving short-segment fusions. AIMS: To determine if spinopelvic alignment affects patient-reported outcome measures (PROMs) after posterior lumbar decompression and fusion (PLDF) with or without a transforaminal lumbar interbody fusion in patients with L4-5 DS. SETTINGS AND DESIGN: A retrospective cohort analysis was conducted on patients who underwent PLDF for L4-5 DS at a single tertiary referral academic medical center. MATERIALS AND METHODS: Patients were divided into groups based on preoperative cutoff values of 20° for pelvic tilt (PT) and 11° for pelvic incidence-lumbar lordosis mismatch (PI-LL) with subsequent reclassification based on correction to <20° PT or 11° PI-LL. Radiographic outcomes and PROMs were compared between the groups. STATISTICAL ANALYSIS USED: Multiple linear regression analyses were performed to determine whether radiographic cutoff values served as the independent predictors of change in PROMs. Statistical significance was set at P < 0.05. RESULTS: A total of 188 patients with completed PROMs were included for the analysis. Preoperative PT >20° was associated with significantly greater reduction in PI-LL (−2.41° vs. 1.21°, P = 0.004) and increase in sacral slope (SS) (1.06° vs. −1.86°, P = 0.005) compared to patients with preoperative PT <20°. On univariate analysis, no significant differences were observed between any groups with regard to PROMs. Preoperative sagittal alignment measures and postoperative correction were not found to be independent predictors of improvement in clinical outcomes. CONCLUSION: A preoperative PT >20° is associated with improved PI-LL reduction and an increase in SS. However, no differences in clinical outcomes were found 1 year postoperatively for patients with preoperative PT >20° and PI-LL ≥11° compared to patients below this threshold.