Baxter's nerve (the first branch of the lateral plantar nerve, inferior calcaneal nerve) arises from the lateral plantar nerve at or just distal to the tarsal tunnel, passing horizontally between the abductor hallucis and flexor digitorum brevis to supply the abductor digiti minimi muscle of the foot. It is the motor nerve to the abductor digiti minimi and carries sensory fibres to the medial calcaneal periosteum and the plantar heel skin at the medial-to-lateral transition zone.
Baxter's nerve entrapment is a recognised but underdiagnosed cause of chronic heel pain, estimated to account for 15-20% of recalcitrant plantar heel pain cases. It produces plantar heel pain similar to plantar fasciitis but is distinguished by point tenderness along the nerve path (between the abductor hallucis and flexor digitorum brevis rather than at the medial calcaneal tuberosity) and by abductor digiti minimi weakness on testing. EMG/NCS may demonstrate denervation in the abductor digiti minimi. Corticosteroid injection along the nerve path and surgical decompression (releasing the fascial bridge between the abductor hallucis and flexor digitorum brevis) are effective treatments.
Baxter's nerve compressed between the abductor hallucis and flexor digitorum brevis or at the medial calcaneal periosteal attachment produces plantar heel pain that fails standard plantar fasciitis treatment; distinguishing features include tenderness medial to the typical plantar fascia insertion point and abductor digiti minimi weakness on resisted little toe abduction.
