External neurolysis as a treatment for foot drop secondary to weight loss: a retrospective analysis of 200 cases

Background Peroneal nerve entrapment is the most common peripheral mononeuropathy of the lower limbs. Foot drop, a common presentation, leads to an impaired eversion and dorsiflexion of the foot. An intriguing observation is the occurrence of foot drop secondary to weight loss. Methods A retrospective study of patients surgically treated for peroneal nerve entrapment was performed between January 1, 1995 and December 31, 2016, at the Department of Neurosurgery, Genk, Belgium. Out of a total of 421 patients, 200 patients with foot drop secondary to weight loss were included. For each subject, motor and sensory outcomes after external neurolysis were investigated. As a primary objective, we examined the postoperative outcomes of external neurolysis as a treatment for foot drop in patients with peroneal nerve entrapment at the fibular head secondary to weight loss. As a secondary objective, we analyzed the correlation between patient characteristics and the success rate of external neurolysis. Results When defining success as a postoperative MRC score of 4 or 5, external neurolysis has a success rate of 85% in patients with foot drop secondary to weight loss. A significant difference (P = < 0.0001) between postoperative and preoperative MRC scores indicates that external neurolysis leads to significant improvement of motor function in patients with foot drop secondary to weight loss. A multiple logistic regression model showed that "preoperative MRC scores" and "duration of symptoms" were the only variables with an impact on postoperative MRC scores. Other variables such as "age," "gender," and "side of entrapment" had no significant impact on postoperative results. Conclusions Statistical analysis emphasizes the important role of external neurolysis in the treatment of peripheral peroneal nerve entrapment. Therefore, external neurolysis at the fibular head should be regarded as a very effective and safe procedure in patients with foot drop secondary to weight loss.