Plantar talar head contusions and osteochondral fractures: associated findings on ankle MRI and proposed mechanism of injury.

OBJECTIVE: To evaluate the significance of plantar talar head injury (PTHI) in predicting osseous and soft tissue injuries on ankle MRI.

MATERIALS AND METHODS: The IRB approved this HIPAA-compliant retrospective study. The study group consisted of 41 ankle MRIs with PTHI that occurred at our institution over a 5 ½ year period. Eighty MRIs with bone injuries in other locations matched for age, time interval since injury, and gender formed a control group. Injuries to the following structures were recorded: medial malleolus, lateral malleolus/distal fibula, posterior malleolus, talus, calcaneus, navicular, cuboid, lateral, medial and syndesmotic ligaments, spring ligament complex, and extensor digitorum brevis (EDB) muscle. Twenty separate logistic regressions determined which injuries PTHI predicted, using the Holm procedure to control for family-wise alpha at 0.05.

RESULTS: PTHI strongly predicted the occurrence of injuries involving the anterior process of the calcaneus [24 % of cases, odds ratio (OR) 12.66], plantar components of the spring ligament (27 %, OR 9.43), calcaneal origin of the EDB and attachment of the dorsolateral calcaneocuboid ligament (22 %, OR 7.22), cuboid (51 %, OR 6.58), EDB (27 %, OR 5.49), anteromedial talus (66 %, OR 4.78), and posteromedial talus (49 %, OR 4.48). PTHI strongly predicted lack of occurrence of syndesmotic ligament injury (OR 19.6). The PTHI group had a high incidence of lateral ligamentous injury (78 %), but not significantly different from the control group (53 %).

CONCLUSIONS: PTHI is strongly associated with injury involving the transverse tarsal joint complex. We hypothesize it results from talo-cuboid and/or talo-calcaneal impaction from a supination injury of the foot and ankle.