The concept of ring of injuries: evaluation in ankle trauma

Radiographs are first-line imaging in ankle trauma but lack sensitivity to detect ligamentous injuries and undisplaced fractures. Our hypothesis was that ankle injuries occur in predefined sequences along two osteoligamentous rings, so that occult injuries non-visible on initial radiographs can be predicted. We, therefore, aimed to validate a ring model of progressive damages in the interpretation of ankle trauma radiographs. This study retrospectively enrolled 277 adult patients that presented an acute fibular fracture on ankle radiographs between May and November 2019. Four different types of fibula fracture were differentiated, each being considered to correspond to a different mechanism of injury. Patients were classified into four groups, upon the appearance of their fibular fracture. Then, injuries to the distal tibiofibular syndesmosis, medial malleolus, and deltoid ligament (medial clear space) were assessed in each patient radiographs. Traumatic injuries were independently evaluated by a resident and an experienced MSK radiologist. For each patient, observed features were compared to those predicted by the ring concept. Inter- and intraobserver agreements were calculated. Injuries were observed according to the predictable sequence in 266 of the 277 patients (96%). In the 11 remaining patients, discordances were presumably due to undisplaced injuries to the syndesmosis or deltoid ligament. Agreements were considered very good for each evaluated item. The Lauge-Hansen ring concept was found to be highly accurate and reproducible for radiographic assessment of ankle injuries. Discordances to the predicted sequence might reflect occult injuries, especially of the syndesmosis or deltoid ligament.