Risk Factors Analysis for Foot Drop Associated with Lumbar Disc Herniation: An Analysis of 236 Patients.

OBJECTIVES

To identify the risk factors for foot drop in patients with lumbar disc herniation (LDH).

METHODS

Two hundred thirty-six patients who underwent surgery for LDH were retrospectively reviewed. Foot drop was defined as tibialis anterior muscle strength of lower than grade 4 by the manual muscle test. Possible risk factors, including demographic and radiographic parameters, were evaluated by multivariate logistic regression analysis.

RESULTS

Fifty-two patients (22.9%) suffered from foot drop. Multivariate logistic regression analysis revealed that diabetes mellitus, disc calcification, patients who had an acute episode or acute-on-chronic episode, and patients who presented with lateral recess or extraforaminal type of disc herniation were at greater risk of foot drop. Notably, patients who had a canal occupancy rate of more than 50% were at greater risk of foot drop compared with patients who had a canal occupy rate of less than 25%. With a 1.0-mm increase in anteroposterior diameter of the index spinal canal, the risk of developing foot drop decreased to 51.8% in these patients (P < 0.05).

CONCLUSIONS

The following factors may affect the development of foot drop in patients with LDH: 1) diabetes mellitus; 2) patients with an acute episode or acute-on-chronic episode; 3) patients with lateral recess or foraminal type of herniation; 4) disc calcification; 5) canal occupancy rate greater than 50%; and 6) the anteroposterior diameter of canal. Surgical treatments for patients with those risk factors should be implemented positively during the follow-up period to reduce possible adverse outcomes.