Spine - 2026-09-07 - Journal Article
Paraspinal Muscle Quality and Functional Outcome After Lumbar Spinal Stenosis Surgery.
Udby PM, Hallager DW, Iljazi A, Andersen MØ, Carreon L
Topics
Key Takeaway
Each one-grade increase in preoperative Goutallier multifidus fatty infiltration reduces the odds of achieving ODI MCID by 27% (OR 0.73) at two years after LSS surgery.
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Summary
This study asked whether preoperative paraspinal muscle quality—quantified by Goutallier multifidus grading and psoas muscle index on MRI—predicts functional outcome after LSS surgery in a Danish National Spine Registry cohort. Increasing Goutallier grade correlated with worse 2-year ODI, less ΔODI improvement (both P=0.028), and reduced MCID attainment (OR 0.73 per grade, P=0.026). Psoas muscle index was not associated with any outcome measure.
Key Limitation
The retrospective design precludes controlling for the type and extent of surgical decompression performed, which is a major confounder of 2-year ODI outcomes independent of muscle quality.
Original Abstract
BACKGROUND
Outcomes after surgery for lumbar spinal stenosis (LSS) vary substantially. Paraspinal muscle quality may reflect functional reserve, but its prognostic value in LSS surgery remains incompletely defined.
PURPOSE
To assess whether preoperative multifidus muscle fatty infiltration and psoas muscle size are associated with functional outcomes after LSS surgery.
STUDY DESIGN
Retrospective cohort study.
METHODS
Patients undergoing surgery for LSS were identified from the Danish National Spine Registry. Preoperative MRI was used to grade multifidus fatty infiltration using the Goutallier classification system and to measure psoas muscle index. The primary outcome was Oswestry Disability Index (ODI) at two-year follow-up. Secondary outcomes included change in ODI from baseline (ΔODI) and achievement of a minimal clinically important difference (MCID; ΔODI ≥12).
RESULTS
A total of 344 patients were included. Psoas muscle index was not associated with ODI at two years (P=0.163), ΔODI (P=0.134), or MCID responder status (P=0.211). In contrast, increasing Goutallier grade was associated with worse ODI at two years and less improvement in ΔODI (both P=0.028), and reduced odds of achieving MCID (OR 0.73 per grade; P=0.026).
CONCLUSION
Preoperative multifidus muscle fatty infiltration is associated with worse long-term functional outcome and a lower likelihood of clinically meaningful improvement after surgery for lumbar spinal stenosis in a dose-response manner, whereas psoas muscle index is not predictive of outcome. Assessment of paraspinal muscle quality on routine MRI may aid in preoperative risk stratification and patient counseling.