LAUSR

Study Design. Prospective multicenter cohort study. Objective. To study the question whether paravertebral muscle quality may affect the clinical outcome of epidural steroid infiltration (ESI) or surgical decompression in patients with symptomatic lumbar spinal stenosis (LSS). Summary of Background Data. To the present, the impact of paravertebral muscle quality on clinical outcome of ESI or surgical decompression in patients with LSS has not been clarified. Methods. The Lumbar Stenosis Outcome Study was used as database. Patients with symptomatic LSS who received an ESI (group I) or lumbar decompression surgery (group II), had a follow-up of at least 12 months and a pretreatment lumbar magnetic resonance imaging were included (n = 205). Paravertebral muscle quality was quantified by the degree of fatty degeneration (according to Goutallier) on the level L3. Clinical outcome was assessed using the Spinal Stenosis Measure, Numeric Rating Scale, Roland and Morris Disability Questionnaire, and EQ-5D-3L sum score. Reinfiltration, surgery following infiltration, or revision was defined as treatment failure. Results. ESI (group I) and surgical treatment (group II) were associated with a failure rate of 60% and 12.7%, respectively. In group I, there was a tendency for the rate of reintervention to be less in patients with bad muscle quality (P = 0.22). In group II, improvements in the clinical outcomes up to 12 months did not differ between Goutallier stage ⩽1 and ≥2. Patients with Goutallier stage ⩽1 had more improvement in Spinal Stenosis Measure symptoms (P = 0.04). Conclusion. Relevant fatty degeneration of the paravertebral musculature, as a sign of low muscle quality, has low impact on clinical outcome and the high failure rates with conservative treatment by ESI compared to surgical decompression. Therefore fatty degeneration has no relevant prognostic value for LSS treatment. Level of Evidence: 2