502 - Can a Fibular Osteophyte Cause Foot Drop?

Case Diagnosis: fibular neuropathy associated with lateral fibular osteophyte

Case Description: 57-year-old male presented with progressive left foot drop, worsening over 2-3 months. Foot drop episodes were associated with anterolateral leg pain, brought on by walking and improved with rest. Electrodiagnostic (EDX) evaluation showed significant slowing of the common fibular motor conduction velocity to the anterior tibialis (AT) and extensor digitorum brevis recording with trace response at ankle. Needle EMG revealed fibrillations limited to the left AT and extensor hallicus longus musculature with associated long duration polyphasic motor units. Left knee radiograph revealed an osteophytic spur on the lateral proximal fibula in the transition area from the fibular head to the neck. The patient declined surgical intervention and unfortunately went on to have progressive and likely permanent foot drop over the next six months, requiring ongoing use of an AFO.

Discussions: The differential diagnosis of “foot drop” includes but is not limited to; sciatic/fibular neuropathy, lumbar plexopathy, CNS etiologies, radiculopathies, and generalized neuropathies. Compression of the fibular nerve (peroneal nerve) at the fibular head can result in varying degrees of paralysis depending upon the nature or degree of compression. We report a potentially rare cause of fibular neuropathy at the knee associated with a large proximal lateral fibular osteophyte with correlating EDX findings. In this case no surgery was performed, so we aren’t certain if decompression would have helped in this situation.

Conclusions: The evaluation of fibular neuropathy (peroneal neuropathy) at the fibular head does not typically include a radiograph of the knee. We propose that a radiograph should be considered in this situation because it may provide an option for treatment. If a proximal fibular osteophyte is associated with foot drop in an adult, we propose surgical evaluation is a reasonable consideration.