Radiographic Accuracy of Identifying Anterolateral Tibial Plafond Involvement in Pronation Abduction Ankle Fractures

Objectives: To evaluate the incidence of anterolateral tibial plafond involvement in pronation-abduction (PAB) ankle fractures and analyze the accuracy of radiographs in detecting anterolateral tibial plafond involvement, impaction, and predicting the need for direct visualization and an articular reduction. Methods: Design: A multi-institutional retrospective chart review Setting: Five level 1 trauma centers in the United States Patient Selection Criteria: Adult patients with PAB ankle fractures (OTA/AO 44B2.3, 44C2.2, 44C2.3) from 2020-2022 were reviewed by 7 fellowship-trained orthopedic trauma surgeons. They were queried about the presence of anterolateral tibial plafond involvement and impaction, and whether they would need direct visualization and an articular reduction using both radiographs and CT. Outcome Measurements and Comparisons: The presence of anterolateral tibial plafond impaction was tabulated separately using radiographs and CT scans. The accuracy of radiographs and changes in surgical plan after CT review were calculated using CT as the gold standard. Results: 61 fractures in 61 patients were evaluated with CT and/or plain radiographs. Using plain radiographs, anterolateral tibial plafond involvement and impaction were identified in 61% and 36% of cases, respectively. In the 38 fractures with both plain radiographs and CT scans, anterolateral tibial plafond involvement was identified in 66% of radiographs and 74% of CT scans (p = 0.4). Plafond impaction was identified in 42% of plain radiographs and 37% of CT scans (p = 0.62). There was no difference in the rate of involvement between radiographs and CT scan. The diagnosis of anterolateral tibial plafond impaction using plain radiographs was correct in 74% of fractures when compared to CT imaging, resulting in a sensitivity of 71%, a specificity of 75%, a positive predictive value (PPV) of 62%, and a negative predictive value (NPV) of 82%. Plain radiographs correctly predicted the need for direct visualization and an articular reduction in 74% of cases and had a PPV of 59% and a NPV of 86%. Conclusions: Anterolateral tibial plafond involvement and impaction was present on CT in 74% and 37% of pronation-abduction (PAB) ankle fractures, respectively. Plain radiographs had higher NPV for identifying impaction and the need for articular reduction than they did sensitivity, specificity or PPV. CT is an important tool for preoperative planning that should be considered when planning for operative fixation of PAB ankle fractures. Level of Evidence: Prognostic level III. See Instructions for Authors for a complete description of levels of evidence.