Paraspinal Muscle Fatty Infiltration Predicts Residual Back Pain and Reoperation after Lumbar Interbody Fusion: A...

Residual back pain and reoperation after lumbar interbody fusion (LIF) remain clinical challenges despite advances in surgical techniques. This study aimed to evaluate whether preoperative paraspinal muscle fatty infiltration (FI), quantified on magnetic resonance imaging (MRI), is independently associated with adverse postoperative outcomes following LIF.

A retrospective cohort of 124 patients who underwent open posterior LIF between April 2020 and December 2024 was analyzed. FI was quantified on axial T2-weighted MRI using region-of-interest segmentation of the multifidus and erector spinae muscles. The primary outcomes were residual postoperative back pain (visual analog scale [VAS] ≥4 at ≥6 months) and reoperation. Multivariable logistic regression and receiver operating characteristic (ROC) analyses using Youden's index were performed.

Residual postoperative back pain occurred in 39% of patients, and reoperation occurred in 17%. Patients with residual postoperative pain had significantly higher FI values than those without persistent symptoms (31% vs. 20%, P < 0.001). Patients requiring reoperation also had significantly higher FI values (33% vs. 24%, P < 0.001). On multivariable analysis, FI remained independently associated with residual postoperative pain (OR 2.41, 95% CI 1.52-3.84, P < 0.001) and reoperation (OR 2.87, 95% CI 1.61-5.11, P < 0.001). ROC analysis demonstrated good discriminative performance, with an area under the curve (AUC) of 0.79 and an optimal cutoff value of 28%.

Increased paraspinal muscle FI was independently associated with residual postoperative back pain and reoperation following LIF. MRI-based assessment of FI may support preoperative risk stratification and help identify patients at increased risk for adverse postoperative outcomes.