Psoas Muscle Health is Correlated with Time to Achieve MCID in Patients with Predominant Axial Back Pain Following Decompression Surgery: Early Results.

STUDY DESIGN:Retrospective cohort study. OBJECTIVE:To determine the impact of psoas muscle health (cross-sectional area, CSA) on achieving minimal clinically important differences (MCID) in patient-reported outcome measures (PROMs) following laminectomy for patients with predominant back pain (PBP) and leg pain (PLP). SUMMARY OF BACKGROUND DATA:Psoas muscle health is linked to postoperative outcomes in decompression patients, with MRI-based grading of psoas CSA correlating with these outcomes. However, evidence on its impact on symptomatic recovery, measured by PROMs, is lacking. METHODS:106 patients with PBP (VAS back >VAS leg) and 139 patients with PLP (VAS leg >VAS back) who underwent laminectomy from 2017-2021 were included. Axial T2 MRI images were analyzed for psoas CSA using a validated method. Based on the lowest-quartile normalized total psoas area (NTPA) thresholds, patients were divided into "Good" and "Poor" muscle health groups. The correlation analyses were performed between the psoas CSA and changes in PROMs. Kaplan-Meier survival analysis was conducted to determine the probability of achieving MCID as a function of time. RESULTS:Of 106 PBP patients, 83 (78.3%) had good muscle health, 23 (21.6%) had poor muscle health. Of 139 PLP patients, 54 (38.8%) had good muscle health, 85 (61.1%) had poor muscle health. In the PBP group, older age was associated with poor muscle health (69.70±9.26 vs. 59.92±15.01, P=0.0002). For both cohorts, there were no differences in the rate of MCID achievement for any PROMs between the good and poor muscle health groups. In the PBP group, Kaplan-Meier analysis showed patients with good psoas health achieved MCID-VAS back and Oswestry Disability Index (ODI) in median times of 14 and 42 days (P=0.045 and 0.015), respectively. CONCLUSION:Good psoas muscle health is linked to faster attainment of MCID, especially in patients with PBP compared to PLP after decompression surgery. LEVEL OF EVIDENCE:3.