Assessment of hip abductor power in patients with foot drop: a simple and useful test to differentiate lumbar radiculopathy and peroneal neuropathy.

Abstract

STUDY DESIGN: Prospective study on a diagnostic test.

OBJECTIVE: To determine the usefulness of hip abductor power assessment in the differential diagnosis of foot drop due to lumbar radiculopathy and peroneal neuropathy.

SUMMARY OF BACKGROUND DATA: Foot drop arises from various neuromuscular conditions. Differential diagnosis obvious in the typical case, however, is often inconclusive. There are few reports regarding the validity of hip abductor power in the differential diagnosis of foot drop.

METHODS: Sixty-one consecutive patients who presented with tibialis anterior weakness Medical Research Council grade of less than 3 were included and underwent neurological examination including the assessment of hip abductor power. Patient demographics, mechanism and pattern of foot drop, neurological findings, and the diagnoses were recorded. Final diagnoses were established on the basis of clinical information, imaging studies, and electrophysiological study in limited cases. Validity and reliability of the hip abductor power assessment in the differential diagnosis of foot drop due to lumbar radiculopathy and peroneal neuropathy were evaluated.

RESULTS: There were 44 men and 17 women, with a mean age of 46.8 years (19-77 yr). The final diagnosis was peroneal neuropathy in 28 patients, lumbosacral plexopathy in 9 patients, lumbar radiculopathy in 21 patients, and sciatic nerve disorder in 3 patients. Concomitant hip abductor weakness was found in 85.7% of lumbar radiculopathy and 3.6% of peroneal neuropathy. The sensitivity and specificity of hip abductor power in the differential diagnosis of foot drop due to the lumbar radiculopathy and peroneal neuropathy were 85.7% and 96.4%, respectively. The positive and negative predictive values were 94.7% and 90%, respectively.

CONCLUSION: Assessment of hip abductor strength is a simple and useful method in the differential diagnosis of foot drop due to lumbar radiculopathy and peroneal neuropathy.