CT assessment of lateral talar displacement in supination-external rotation ankle fractures: Correlation with treatment decisions.

Abstract

Conventional radiographs often fail to accurately quantify lateral talar displacement in supination-external rotation (SER) ankle fractures. This study evaluated a CT-derived parameter-lateral talar displacement (LTD)-as an objective surgical indicator by assessing its correlation with treatment decisions. Retrospective comparative study. We retrospectively reviewed CT images of 124 SER ankle fractures. Patients were categorized into conservative (n=44) and surgical (n=80) treatment groups, with 80 non-fracture individuals serving as normal controls. LTD was measured on coronal CT images at the level of the fibular notch. Inter- and intraobserver reliability were assessed using intraclass correlation coefficients. Group comparisons were performed using one-way analysis of variance, and receiver operating characteristic (ROC) curve analysis determined the optimal threshold for predicting surgical intervention. LTD demonstrated excellent interobserver and intraobserver reliability. Mean LTD was -1.0 ± 0.7 mm in normal controls, -0.9 ± 0.7 mm in the conservative group, and 3.5 ± 3.0 mm in the surgical group (p < 0.001). LTD increased progressively with SER stage: stage 2, -0.8 ± 0.8 mm; stage 3, 0.4 ± 1.5 mm; stage 4, 4.0 ± 3.1 mm (p < 0.001). ROC analysis yielded an area under the curve of 0.976 (95% CI 0.952-1.000), with an LTD threshold > 1 mm providing 86% sensitivity and 96% specificity for predicting surgical intervention. LTD is a reliable parameter for quantifying lateral talar displacement. A threshold greater than 1 mm accurately identifies fractures that require surgical stabilization and serves as a valuable adjunct to conventional radiographic assessment.