Radiographic identification of the primary lateral ankle structures.

BACKGROUND Lateral ankle ligament injuries rank among the most frequently observed athletic injuries, requiring repair or reconstruction when indicated. However, there is a lack of quantitative data detailing the ligament attachment sites on standard radiographic views. PURPOSE To quantitatively describe the anatomic attachment sites of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL) on standard radiographic views with respect to reproducible osseous landmarks to assist with intraoperative and postoperative assessment of lateral ankle ligament repairs and reconstructions. STUDY DESIGN Descriptive laboratory study. METHODS Twelve nonpaired, fresh-frozen cadaveric foot and ankle specimens were dissected to identify the origins and insertions of the 3 primary lateral ankle ligaments. Ligament footprint centers were marked with 2-mm stainless steel spheres shallowly embedded at the level of the cortical bone prior to obtaining standard lateral and mortise radiographs. Measurements were performed twice by 2 blinded raters independently to calculate mean distances and assess reliability via intraclass correlation coefficients (ICCs). RESULTS Radiographic measurements demonstrated excellent reproducibility between raters (all interobserver ICCs>0.97) and across trials (all intraobserver ICCs>0.99). On the lateral view, the ATFL fibular attachment (mean±SD) was 8.4±1.8 mm proximal and anterior to the inferior tip of the lateral malleolus and attached on the talus 13.8±2.0 mm proximal and anterior to the apex of the lateral talar process. The CFL originated 5.0±1.4 mm superior and anterior to the inferior tip of the lateral malleolus and inserted on the calcaneus 18.5±4.6 mm posterior and superior to the posterior point of the peroneal tubercle. On the mortise view, the ATFL origin was 4.9±1.4 mm proximal to the inferior tip of the lateral malleolus and inserted on the talus 9.0±2.1 mm medial and superior of the apex of the lateral talar process and 18.9±3.1 mm inferior and slightly lateral to the superior lateral corner of the talar dome. The fibular CFL origin was 2.9±1.6 mm proximal and slightly medial to the inferior tip of the lateral malleolus and inserted on the calcaneus 18.0±5.1 mm distal to the apex of the lateral talar process. CONCLUSION Radiographic parameters quantitatively describing the anatomic origins and insertions of the lateral ankle ligaments were defined with excellent reproducibility and agreement between reviewers. CLINICAL RELEVANCE Quantitative radiographic anatomy data will assist in preoperative planning, improve intraoperative localization, and provide objective measures for postoperative assessment of anatomic repairs and reconstructions.