Association Between Metatarsophalangeal Joint Instability and Sensory Disturbances in the Toes.

Abstract

Metatarsophalangeal (MTP) joint instability may cause forefoot sensory disturbances, often misattributed to Morton's neuroma. This study investigated the association between MTP joint instability and sensory disturbances. Thirty-three patients were enrolled, including 58 feet in total. All patients underwent surgery for moderate to severe hallux valgus, and in unilateral cases, the contralateral foot was also included when eligible. MTP instability was classified as stable, subluxed, or dislocated using the drawer test under fluoroscopy. Sensory disturbances in the 2nd-4th web spaces were evaluated with the Semmes-Weinstein monofilament test. Instability was most frequent in the 2nd (69.0%) and 3rd (65.5%) toes. Sensory disturbance rates in the 2nd and 3rd web spaces were significantly higher in feet with instability in both the 2nd and 3rd MTP joints compared to stable feet (P = .02, P = .03), while no significant difference was found for the 4th web space (P = .42). MTP joint instability may cause sensory disturbances by affecting adjacent plantar digital nerves and should be considered in clinical evaluations. Level IV, prospective case series.