Snowboarder's talus fracture. Mechanism of injury.

Fracture of the lateral process of the talus is an injury unique to snowboarders and is of particular clinical relevance because it masquerades as an anterolateral ankle sprain and is difficult to detect on standard radiographic views. Misdiagnosis can lead to long-term morbidity in a young and active population, with ensuing severe degeneration of the subtalar joint. To date, the precise mechanism of injury has not been established, making it difficult to identify potential preventive strategies in equipment design or snowboarding technique. Fracture of the lateral process of the talus in snowboarders has been thought to result from pure dorsiflexion and inversion combined with axial loading. We hypothesized, however, that external rotation is a key component of the mechanism of injury. Ten cadaveric ankles were mounted on a materials testing machine in a position of fixed dorsiflexion and inversion. All ankles were loaded to failure axially, with or without combined external rotation. No fractures occurred after axial loading in dorsiflexion and inversion, but six of eight specimens sustained fractures of the lateral process of the talus when similarly loaded with external rotation added, supporting our hypothesis. Further study is needed to evaluate the relationship between various types of snowboarding equipment and fracture mechanism.