[Irreductable lateral subatalar fracture-dislocation by entrapment of the posterior tibial neurovascular bundle: case report].

Introduction: subtalar dislocations, typical of high-energy trauma, are classified as medial, lateral, anterior or posterior depending on the deviation of the foot in relation to the talus. Lateral dislocation accounts for 17% of the total and has a worse prognosis. Immediate reduction is required to reduce the risk of sequelae, the incidence of which is around 90%.

Objective: a case of lateral subtalar dislocation is presented; a review of the literature on its diagnosis, treatment and prognosis is carried out.

Clinical case: a 46-year-old woman fell from a height of 3 meters, with severe deformity in the hindfoot. There was good distal vascular coloration, but no pulse or posterior tibial sensitivity could be identified. In addition, she had a medial sulcocutaneous fold under the head of the talus. Plain radiograph and CT revealed lateral subtalar dislocation, with fracture of the sustentaculum tali, and a "fleck sign" in the posterior region of the distal fibula. Suspecting soft tissue incarceration, a medial approach was performed, observing interposition of the posterior tibial neurovascular bundle. After joint reduction, the sustentaculum tali and the "fleck sign" were osteosynthesized. In addition, a complete section of the long lateral peroneal tendon was identified, which was tenodesed to the short peroneal tendon. Finally, an external fixator was placed. After eight weeks, the fixator was removed and weight bearing was authorized; after six months, mobility was complete and hypoesthesia persisted only in the plantar pad.

Conclusions: lateral subtalar dislocation is an uncommon entity with a poor prognosis. Adequate interpretation through a thorough examination and pre-reduction CT of the bone and soft tissue lesions minimizes future sequelae.