Morton neuroma involves the common plantar digital nerve of the third web space (between the third and fourth metatarsal heads) in approximately 80% of cases, where the medial plantar nerve branch meets the lateral plantar nerve branch. The nerve at this interspace is subject to repetitive compression between the metatarsal heads and the intermetatarsal ligament, leading to perineural fibrosis, demyelination, and nerve enlargement.
Morton neuroma presents as forefoot pain and burning paraesthesia in the third-fourth toe cleft, worsened by tight footwear and high heels, reproduced by the Mulder click (squeezing the metatarsal heads while pressing the web space). Ultrasound and MRI confirm the enlarged nerve at the interspace. Conservative treatment with wide footwear and corticosteroid injection has a 50% success rate. Surgical excision via a dorsal approach or plantar approach removes the enlarged nerve segment and the intermetatarsal bursa, with the plantar approach providing direct access but a painful plantar scar.
Perineural fibrosis of the common plantar digital nerve between the third and fourth metatarsal heads produces forefoot burning pain and toe paraesthesia reproduced by the Mulder click test; ultrasound identifies the fusiform enlargement at the intermetatarsal space and surgical neurectomy via the dorsal interspace provides definitive treatment.
