Computed Tomography-Based Comparison of Anterior and Posterior Cortical Thickness Around the Interfragmentary Screw Fixation Level in Weber B Lateral Malleolar Fractures

Background/Objectives: Cortical morphology around the screw fixation level may influence screw purchase in Weber B lateral malleolar fractures. This study compared anterior and posterior cortical thickness of the distal fibula around the interfragmentary screw fixation level using preoperative computed tomography (CT) images matched with postoperative radiographs. Methods: This retrospective radiographic study included 155 patients who underwent operative treatment for Weber B lateral malleolar fractures using an interfragmentary screw between 2019 and 2023. Patients with Weber A or C fractures, no preoperative CT, fixation without an interfragmentary screw, previous ipsilateral lateral malleolar fracture or surgery, or unreliable CT measurement were excluded. The levels at which the screw crossed the anterior and posterior cortices were identified on postoperative radiographs and transferred to sagittal CT images. Results: The anterior cortex was significantly thicker than the posterior cortex (2.44 ± 0.82 mm vs. 1.39 ± 0.66 mm; mean difference, 1.05 mm; 95% confidence interval, 0.94–1.17; p < 0.001). This anterior cortical predominance was observed across all sex- and age-based subgroups. Men had greater anterior and mean cortical hickness than women, while patients aged <60 years had greater cortical thickness than those aged ≥60 years. Conclusions: Around the interfragmentary screw fixation level in Weber B lateral malleolar fractures, the anterior cortex was consistently thicker than the posterior cortex. Given the limitations of radiograph-to-CT matching, the results should be interpreted as demonstrating a relative regional pattern rather than exact absolute cortical thickness values. This pattern may provide useful reference information when planning screw fixation.