Lumbar Multifidus Intramuscular Fat Concentrations are Associated With Recovery Following Decompressive Surgery for Lumbar Spinal Stenosis

Spine 2026;51:25–33

This longitudinal cohort study investigates whether preoperative intramuscular fat (IMF) in lumbar paraspinal muscles predicts five-year recovery and surgical success after decompressive surgery for lumbar spinal stenosis causing intermittent neurogenic claudication. Using automated MRI segmentation and quantitative IMF thresholds, outcomes included global perceived effect, Zurich Claudication Questionnaire-based surgical success, pain VAS, and disability scores.

Key findings show lower preoperative multifidus IMF (but not erector spinae IMF) was associated with higher rates of perceived recovery, surgical success, and reduced long-term disability over five years. No consistent relationship was found between IMF and leg or back pain trajectories; results were adjusted for age, BMI, sex, smoking, reoperation, and surgical technique.

Lumbar multifidus intramuscular fat (IMF): Lower preoperative IMF in the lumbar multifidus muscle is associated with higher rates of perceived recovery and surgical success after decompression surgery for lumbar spinal stenosis (LSS) over a five-year period.

Erector spinae IMF: Preoperative IMF levels in the erector spinae muscle are not significantly associated with recovery or surgical success following LSS surgery.

Disability outcomes: Patients with nonsevere IMF in the right lumbar multifidus experience less postoperative disability for up to five years compared to those with severe IMF.

Pain outcomes: No significant association exists between preoperative paraspinal IMF (either muscle) and the clinical course of leg or back pain intensity after surgery.

IMF quantification method: Automated MRI-based quantification and categorization of IMF (<50% = nonsevere, ≥50% = severe) using computer vision models enables objective assessment of paraspinal muscle health.

Prognostic value: Assessing lumbar multifidus IMF preoperatively can improve prediction of which patients are at risk for poor recovery and help tailor individual interventions.

Study limitations: Missing data (up to 32% at five years), dichotomized IMF classification, and limited field-of-view for some muscles may affect precision; more detailed and larger studies are needed.

Clinical implication: Routine IMF assessment may enhance clinical decision-making and rehabilitation strategies for patients undergoing lumbar decompressive surgery.