Rupture of the Tibialis Posterior Tendon With Associated Bimalleolar Ankle Fracture.

Abstract

The acute traumatic rupture of the tibialis posterior tendon in association with closed ankle fractures is rare and often under-recognised. If recognised early, outcomes can be excellent. There are 28 known cases in the literature, and we report two further cases associated with bimalleolar ankle fracture dislocation. A 49-year-old presented with valgus deformity at the ankle joint and global tenderness following a work injury as a mechanic. A plain radiograph showed a displaced oblique comminuted fracture of the lateral malleolus with valgus angulation at a syndesmosis, with significant talar shift. The patient underwent open reduction and internal fixation with a seven-hole, one-third tubular plate and screws. A 35-year-old involved in a motorcycle collision with a car presented with swollen left ankle and valgus deformity. Plain radiographs revealed bimalleolar fracture subluxation. Closed reduction was unsuccessful and hence direct medial approach demonstrated a complete rupture of the posterior tendon. The medial malleolus was fixed using lag screws and washers. The tendon was repaired using the modified Kessler technique in both cases. The tibialis posterior plays a significant role in foot and ankle biomechanics due to its broad tendinous insertion. Acute traumatic rupture is rare, as it is protected due to its deep-seated anatomic location within the deep posterior compartment of the leg. Preoperative diagnosis of this injury is challenging and hence this diagnosis is often made intraoperatively. In both cases, there was a retraction of the proximal end beyond incision margins, and this can make tendon rupture difficult to identify intraoperatively as well. Upon identification, assessment of the tendon for degenerative changes was key to deciding upon suitability for primary repair. Despite its rarity, a high index of suspicion should be maintained in fracture dislocation of the ankle joint, especially when the mechanism is known to be pronation-external rotation.