The Influence of Paraspinal Sarcopenia on Patient-Reported Outcomes Following Lumbar Fusion

Study Design: Retrospective cohort study. Objective: To analyze the ability of various quantitative, MRI-based measures of spine-specific sarcopenia to predict patient-reported outcomes following lumbar fusion surgery. Summary of Background Data: Sarcopenia is an established risk factor for poor outcomes and complications in spine surgery. However, a lack of consensus exists on how to optimally quantify paraspinal sarcopenia for outcome prediction. Furthermore, few studies have investigated the ability of MRI-based measures of sarcopenia to predict Patient-Reported Outcome Measure Information System (PROMIS), physical function (PF), and pain interference (PI) scores after lumbar fusion surgery. Methods: Included patients underwent lumbar fusion surgery at a single, tertiary academic center and had a lumbar MRI within 1 year before surgery. Demographic factors were collected, and lumbar paraspinal muscle (ie, multifidus, psoas, and erector spinae) cross-sectional area (CSA) and fatty infiltration (FI) were measured by 2 reviewers. All variables were compared on bivariable and multivariable analyses between patients who did versus did not meet a minimum clinically important difference (MCID) of 8 on PROMIS-PF and PROMIS-PI scores. Results: Of the 87 patients who met inclusion criteria, 59 patients met MCID for physical function (PF) while 57 patients met MCID for pain interference (PI). Bivariable analysis revealed no differences in demographic variables or CSA between MCID and non-MCID groups. Psoas FI demonstrated a trend towards significance for PROMIS-PF [MCID: 8.37 (±5.45) vs. non-MCID: 10.9 (±6.03), P =0.055], and baseline PROMIS-PI scores were higher in patients that met MCID for PROMIS-PI [67.2 (±4.79) vs. 62.9 (±7.78), P =0.005]. With multivariable analysis controlling for confounders, increasing psoas FI lowered the odds of meeting PROMIS-PF MCID (OR=0.90, P =0.033, 95% CI=0.82–0.99). Conclusions: Patients with increased psoas FI were less likely to see improvements in physical function after controlling for comorbidity burden and frailty. However, the effect size was relatively small.