Background:Tillaux-Chaput fractures (TCFs) occur in the anterolateral rim of the distal tibia. TCFs are often overlooked on radiographic review, increasing the risk of chronic pain, instability, and ankle osteoarthritis. This study evaluated the effect of the computed tomography (CT) scan on preoperative planning for TCFs in adults.Methods:A retrospective review of ankle fractures evaluated from 2013 to 2023 at a university hospital was conducted. The inclusion criteria were patients >= 18 years of age who underwent radiographic and CT evaluation and had a TCF that was confirmed by CT. The exclusion criteria included pilon and distal tibial fractures and prior ankle surgery. Three orthopaedic surgeons assessed radiographs, classified TCFs using the Rammelt classification, formulated a treatment plan (conservative versus surgical), and, if a surgical treatment was indicated, determined the patient positioning, fixation type, and approach for the TCF. After evaluating CT images, changes in treatment strategy were recorded. Forward stepwise regression was utilized to analyze variables associated with modifications in preoperative planning.Results:A total of 481 fractures had ankle radiographs and CT scans; of these, 83 (17.3%) had a TCF. After the CT evaluation, the Rammelt classification and the surgical decision changed by 69.1% and 12.5%, respectively. Changes in patient positioning, the type of fixation, and the surgical approach for a TCF (when surgery was indicated) occurred in 32.1%, 43.8%, and 35.3% of all cases, respectively. Multivariable analysis showed that the detection of a TCF on CT predicted changes in the surgical decision and fixation type, while changes in the TCF classification predicted modifications in the fixation type and surgical approach. Posterior malleolar fractures were the unique predictor of changes in the patient positioning.Conclusions:CT evaluation modified the surgical decision, type of fixation, and surgical approach for a TCF in 12.5%, 43.8%, and 35.3% of cases, respectively. Moreover, the detection of a TCF and a change in the classification after CT evaluation were predictors of a change in treatment strategy. These findings underscore the importance of the CT scan in the preoperative planning for TCFs in adults. Therefore, we strongly recommend conducting a CT scan when a TCF is suspected in adult patients.Level of Evidence:Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.