Surgical outcomes of unilateral painful foot drop secondary to lumbar disc herniation: a multicenter retrospective study

Abstract

Objective: Foot drop is characterized by weakness in ankle dorsiflexion, primarily due to failure of activation of dorsiflexor muscles secondary to neural compromise. The aim of this study was to evaluate surgical outcomes for unilateral painful foot drop secondary to lumbar disc herniation, specifically excluding cases with cauda equina syndrome.

Methods: This retrospective study spanned 7 centers, focusing on adult patients who underwent lumbar discectomies from September 2011 to September 2022 due to painful unilateral foot drop (Medical Research Council [MRC] grade ≤ 3). Clinical records were analyzed to identify patients matching the inclusion criteria, with data collection adhering to PROCESS guidelines. Outcomes were assessed based on the MRC scale for muscle strength, and statistical analysis was conducted to determine outcome predictors.

Results: This study included 75 patients (mean age 49.03 years, 1:1.007 male/female ratio). Early surgery in younger and less frail patients was associated with better outcomes, with no precise surgical timing cutoff identified. Improvement in MRC grades was seen in 41 patients (55%), with no change in 23 patients (31%) and worsening grades in 11 patients (15%). For every day delaying surgery, the likelihood of improvement decreased by 0.2%. The severity of foot drop was associated with a reduced likelihood of complete resolution, although some recovery was demonstrated. Functional recovery was consistently higher in patients with higher presenting MRC grades. Radicular pain consistently improved following surgical intervention irrespective of all other analyzed metrics.

Conclusions: Prompt surgical intervention for patients with foot drop improved outcomes, especially in those who were younger and less frail. While the study did not identify a specific cutoff for the timing of surgery, the findings emphasize the importance of early surgical consideration as delays were associated with reduced likelihood of recovery. Future research should focus on prospective studies to validate these findings and refine guidelines for surgical intervention in this patient population.

Keywords: degenerative; foot drop; lumbar disc herniation.