How do spinopelvic parameters influence patient-reported outcome measurements after lumbar decompression?

Background context: Spinopelvic parameters indicative of sagittal imbalance include a pelvic tilt (PT) greater than 20° and a mismatch between pelvic incidence (PI) and lumbar lordosis (LL) greater than 10°. However, unlike in fusion surgery, the relationship between spinopelvic parameters and patient-reported outcome measurements (PROMs) in patients undergoing lumbar decompression surgery for neurologic symptoms is less clear. Purpose: To determine whether PROMs are affected by the amount of residual (postoperative) PI-LL mismatch or PT in patients undergoing one- to three-level lumbar decompression surgeries.

Design: Retrospective cohort study (Level of Evidence: III). Patient sample: Patients undergoing between one to three levels of lumbar decompression surgery at a single, academic institution. Outcome measures: PROMs-including the PCS-12, MCS-12, ODI, and VAS Back and Leg pain scores-and radiographic measurements of spinopelvic parameters.

Methods: Patients were separated into groups based on a postoperative PI-LL mismatch of ≤10° or >10° and a postoperative PT<20° or ≥20°. Absolute PROM scores, the recovery ratio (RR) and the percentage of patients achieving Minimum Clinically Important Difference between groups were compared and a multiple linear regression analysis was performed.

Results: A total of 167 patients were included, with 27 patients in the PI-LL>10° group and 91 patients in the PT≥20° group. All groups exhibited significant improvement after surgery for each PROM included (p<.05) except for MCS-12 scores in the PI-LL≤10° group and both PT groups. Comparing between groups, all patients were similar with respect to preoperative scores, postoperative scores, change in scores, recovery ratios, and percentage change in Minimum Clinically Important Difference, except that patients with PT≥20° had higher pre- and postoperative VAS Back scores (p=.036 and p=.024, respectively). With multiple linear regression, postoperative PI-LL>10° and PT≥20° were not significant predictors of worse outcomes for any measured PROM.

Conclusions: Patients with postoperative measurements PI-LL>10° and PT≥20° without instability had similar PROMs at 1 year after limited lumbar decompression when compared to patients without a spinopelvic mismatch.