The Extensor Digitorum Brevis is an easily visualised superficial muscle present on the dorsolateral aspect of the foot. It is innervated by the terminal branches of L5. Wasting of this muscle has been described as a sign of L5 radiculopathy, however its specificity and sensitivity as a clinical sign in patients with disc disease has never been assessed to the best of our knowledge.

The purpose of our study was to determine the effectiveness of this sign in patients with a know L5 radiculopathy. We included three groups of patients, which were prospectively assessed by a blinded single examiner. Group A were patients with a clinical L5 radiculopathy confirmed on MRI, Group B were patients with a clinical a S1 radiculopathy confirmed on MRI and Group C were a control group. There were 20 patients in each group, 10 male and 10 female, mean age 38 years (range 19 – 57 years). Our inclusion criteria were leg pain greater than 6 weeks, we excluded and patient with a history of previous disc disease or foot surgery. A positive sign was defined as a gross clinical wasting of the extensor digitorum brevis compared to the opposite foot.

The sign was negative in all 20 patients in the control group. The sign was positive in 12 patients (60%) with L5 radiculopathy and only one patient (5%) with S1 radiculopathy. Fishers exact test confirmed statistical significance between the two groups with a p value of < 0.05.

We conclude that this easily performed objective clinical sign, when used inpatients with leg pain, is highly specific in determining the pressure of an L5 root involvement.