MRI-defined lumbar fasciitis is associated with inferior subjective outcomes after endoscopic decompression for...

To examine factors associated with unfavorable subjective outcomes at 12 months after endoscopic decompression for LSS, with a specific focus on the role of MRI-defined lumbar fasciitis, and to explore plausible mechanistic implications.

In this retrospective single-center study, 105 patients undergoing endoscopic decompression for lumbar spinal stenosis were included. Baseline clinical characteristics, perioperative laboratory parameters, CT-based radiographic indices, and MRI-derived paraspinal muscle measurements were collected. Lumbar fasciitis was defined as an MRI-based phenotype characterized by edema-like signal alterations in the thoracolumbar fascia. Univariate analyses were performed to compare variables between favorable and unfavorable MacNab outcome groups at 12 months. Variables with p < 0.05 were entered into multivariate logistic regression, and Firth penalized logistic regression was additionally performed to reduce potential small-sample bias due to the limited number of unfavorable outcomes (n = 13).

Among 105 patients, 92 (87.6%) achieved favorable MacNab outcomes and only 13 (12.4%) experienced unfavorable outcomes. Lumbar fasciitis was significantly more frequent in the unfavorable group (12/13 vs. 45/92, p = 0.003). In multivariate logistic regression, concomitant lumbar fasciitis remained independently associated with unfavorable outcomes (odds ratio = 15.46, 95% confidence interval: 1.63-146.7, p = 0.018). Other variables, including age, operation time, medial facetectomy angle, postoperative red blood cell count, and relative paraspinal muscle areas, were not independently associated. Results were consistent in Firth penalized logistic regression, which supported the robustness of the association despite the limited number of unfavorable outcomes.

MRI-defined lumbar fasciitis was associated with inferior subjective outcomes at 12 months after endoscopic decompression for lumbar spinal stenosis. This association remained significant after adjustment for relevant clinical variables and was further supported in a Firth penalized logistic regression model. These findings suggest that MRI-defined fascial signal alterations may represent a clinically relevant pain-related phenotype associated with postoperative patient-reported outcomes. Further prospective studies are warranted to clarify the underlying mechanisms and validate the clinical significance of this association.