Marginal impaction associated with posterior malleolar fracture in rotational ankle injury

This study aimed to introduce the circle drawing method for the evaluation of marginal impaction associated with posterior malleolar fractures (PMFs) on computed tomography (CT) images and evaluate the marginal impaction based on PMF patterns (Bartonícek classification) in rotational ankle fractures.

From January 2014 to December 2019, A total of 299 patients were reviewed retrospectively. The circle drawing method consists of matching the articular surface of the intact tibial plafond with a best-fitted circle on the sagittal CT image. The mismatch gap between the circle and the articular surface indicates the presence of marginal impaction. To validate the circle drawing method, we assessed CT images of 60 ankles without fracture at the medial, central, and lateral parts using the new method.

Based on the review of the preoperative CT scan, 153 out of 299 patients (51.2%) were identified as having PMFs. Among them, 57 patients (37.3%) had marginal impaction associated with PMFs. For small posterolateral type 2 fractures, 58% of patients (47/81) had marginal impaction, and its incidence was most frequent among all types (P<.01). For posteromedial extended type 3 fractures, 27% of patients (8/30) had marginal impaction. Extraincisural type 1 and large posterolateral triangular type 4 fractures were rarely associated with marginal impaction. Among the 180 zones of 60 ankles without fracture, 171 zones (95%) were perfectly fitted to a best-fitted circle.

The marginal impaction associated with PMFs is often observed in rotational ankle fractures, particularly in small posterolateral and posteromedial extended fractures.