Morphological characteristics in non-traumatic osteochondral lesions of the talus: a radiographic study.

Introduction: Osteochondral lesions of the talus (OLT) are frequently associated with trauma; however, the severity and mechanism of injury vary widely, making it difficult to clarify predisposing morphological factors. In contrast, non-traumatic OLT cases may reflect intrinsic anatomical characteristics that contribute to lesion development independent of injury. This study aimed to identify the radiographic morphological features of the ankle in patients with non-traumatic OLT and to elucidate inherent structural factors associated with its occurrence.

Methods: Fifteen ankles (8 males, 7 females) of medial OLT patients without a history of trauma or ankle instability (OLT group) and 15 healthy control ankles (7 males, 8 females) were included in the study. Radiological assessment was conducted using standing frontal and lateral views of ankle joint radiography. A cutoff value was determined based on receiver operating characteristic (ROC) curve analysis and decision criteria. Statistical significance was set at p <.05.

Results: The OLT group exhibited statistically significantly larger tibial medial malleolus angle (TMM; p = .02, Cohen's d = 0.90), and transverse diameter of the tibia plafond (TTiP; p = .006, Cohen's d = 1.15), but a shorter vertical distance between the tibia plafond and the tip of the medial malleolus (VTiPMM; p = .02, Cohen's d = 0.92) compared to the control group. Additionally, the radius of the tibial plafond (RTiP; p = .01, Cohen's d = 1.27) and talar dome (RTaD: p = .014, Cohen's d = 0.88) were smaller in the OLT group, while the medial malleolar length showed no statistically significant difference. ROC curve and area under the curve analysis demonstrated moderate accuracy for four parameters: TTiP, TMM, VTiPMM, and RTiP. The optimal cutoff values for predicting OLT were: TTiP at 44.3 mm, TMM at 19.6°, VTiPMM at 23.4 mm, RTiP at 81.9 mm, and RTaD at 82.8 mm.

Conclusion: Focusing on non-traumatic cases allowed us to identify intrinsic ankle morphology that predisposes to medial talar stress and OLT. These radiological parameters may aid in the diagnosis of non-traumatic OLT and enhance understanding of its pathophysiology.

Level of evidence: Level 3 (case-control study).