The lateral talar dome osteochondral fracture has been described as shallow or wafer-shaped and is more likely to have an associated flake fracture than medial injuries. Displacement into the extracurricular space, however, is a rare occurrence. We present a case of ankle trauma with persistent pain and edema. A CT scan revealed a displaced osteochondral fracture of the lateral dome of the talus and an avulsion fracture of the tip of the medial malleolus. After appropriate dissection and exposure, the fragment was found below the skin, outside the ankle joint capsule. The fragment was fixed to the neck of the talus, and the deltoid ligament and anterior inferior tibiofibular ligament were repaired. After a one-year follow-up, full recovery was achieved without pain, stiffness, or osteonecrosis of the displaced fragment. Although the extra-articular displacement of lateral talar dome osteochondral fractures is rare, it should be considered when assessing ankle trauma.

OBJECTIVE: This study aimed to determine the anatomical risk factors that may play a role in the etiology of medial-sided osteochondral lesions of the talus (OLT) using morphological parameters in magnetic resonance imaging (MRI).
METHODS: One hundred twenty-four patients with medial-sided OLT and age- and sex-matched 124 controls were included in this retrospective study. Two examiners conducted independent OLT classification and measurements of five MRI parameters: tibial axis-medial malleolus angle (TMM), the anterior opening angle of the talus (AOT), talus position (TalPos), the ratio of the distal tibial articular surface to the length of the trochlea tali arc (TAS/TAL), depth of the incisura fibularis (IncDep). Statistical analysis included intraclass correlation coefficients, independent t-tests, receiver-operating characteristic (ROC) analysis, area under the curve (AUC) calculation, and logistic regression analysis. A p-value < 0.05 was considered statistically significant.
RESULTS: TTM, AOT, TalPos, and TAL values were significantly higher and the TAS/TAL ratio was significantly lower in the case group than in the control group (p < 0.001). Cut-off and AUC values for TMM were 15.15° (AUC 0.763), AOT 13.05° (AUC 0.826), TalPos 0.75 mm (AUC 0.887), TAL 35.45 mm (AUC 0.642), and TAS/TAL ratio 0.82 (AUC 0.784), p < 0.001. Multivariate logistic regression analysis results were odds ratio (OR) = 6.1 for TMM ≥ 15.15°, OR = 8.9 for AOT ≥ 13.05°, OR = 36.1 for TalPos ≥ 0.75 mm, and OR = 6.7 for TAS/TAL ratio ≤ 0.82.
CONCLUSIONS: Ankle morphology might have an influence on OLT development. The talus position (TalPos) and anterior opening angle of the talus (AOT) seemed to be the strongest predisposing factors.