A simple test to assist with the diagnosis of common fibular nerve entrapment and predict outcomes of surgical decompression.

BACKGROUND: Common fibular (peroneal) nerve (CFN) entrapment is the most frequent nerve entrapment in the lower extremity. It can cause pain, sensory abnormalities, and reduced ability to dorsiflex the foot or a drop foot. A simple test to assist with diagnosis of CFN entrapment is described as an adjunctive clinical tool for the diagnosis of CFN entrapment and also as a predictor of successful surgical decompression of a CFN entrapment. METHODS: The test, a lidocaine injection into the peroneus longus muscle at the site of a common fibular nerve entrapment, was studied retrospectively in 21 patients who presented with a clinical suspicion of CFN entrapment. Patients ages ranged from 17 to 71 (mean 48.5). RESULTS: The lidocaine injection test (LIT) was positive in 19 patients, and of these, 17 underwent surgical decompression and subsequently experienced improved ability to dorsiflex their foot and reduced sensory abnormalities. CONCLUSION: The LIT is a simple, safe adjunctive test to help diagnose and also predict a successful outcome of surgical decompression of a CFN entrapment. The proposed mechanism of action of the LIT could lead to new, non-surgical treatments for CFN entrapment.