Equinus foot deformity and malunion of the medial malleolus caused by tibialis posterior tendon interposition following irreducible fracture dislocation of the ankle: A case report and literature review.

We report a case of equinus foot deformity and malunion of the medial malleolus caused due to tibialis posterior tendon interposition following irreducible fracture-dislocation of the ankle. A 19-year-old female patient was referred to our hospital with the chief complaint of persistent ankle pain and restricted ankle dorsiflexion. Her medical history revealed a fracture-dislocation of the ankle in the left tibia at the age of 18 years. Open reduction and osteosynthesis were performed 3 days after injury. One year after the operation, ankle pain and restricted ankle dorsiflexion persisted. Computed tomography revealed malunion of the medial malleolus and an irregular groove in the interosseous space between the tibia and fibula. Magnetic resonance imaging revealed entrapment of the tibialis posterior tendon within the posterior talocrural joint and syndesmosis, preventing posterior translation of the talus back to its normal position and forcing the fibula to remain anteriorly displaced in the syndesmosis. We performed several procedures, including reduction of the tibialis posterior tendon interposition and dislocation of the talus, augmentation of the tibio-fibular ligament, and recession of the gastrocnemius. Finally, the patient achieved plantigrade stance and improvement in her Japanese Society for Surgery of the foot ankle/hindfoot scale from 42 to 82 points, after a 2-year follow-up. Anterior impingement caused the patient to experience severe osteoarthritis. Early reduction of the tibialis posterior tendon should have been achieved for this case. Age, fracture type, and severely restricted range of motion should raise suspicion of this adverse event. Level of Clinical Evidence: 4.