Mechanism of Injury

Fractures of the lateral process of the talus are frequently missed at initial evaluation in the emergency room because the symptoms are similar to those seen in the ubiquitous inversion ankle sprain.1-3 Mills and Horne reviewed 39 lateral process fractures in 5 different series and revealed that only 59% were correctly diagnosed.3 For that reason, understanding the mechanism of the sustained injury is critical to identifying the fracture for appropriate treatment. Late diagnosis, as well as the articular nature of the injury, frequently lead to nonunion, osteonecrosis, impingement, traumatic arthritis, and disability. Therefore, it should be part of the differential diagnosis after an ankle injury for both acute and chronic pain. This fracture has more recently been termed “snowboarder’s fracture” or “snowboarder’s ankle” because of the frequency with which it is seen in this sport.4-7 Sudden impact into forced dorsiflexion after the foot is set in eversion is a common maneuver not only on snowboards but on skateboards as well. Other situations where this fracture occurs includes motor vehicle collisions (foot braced against the brake peddle or floorboards), stepping suddenly into a hole while in forward motion, falls from a height, or direct trauma.1,2,7 Since first reported in 19438,9 there has been some controversy regarding incidence, mechanism, and treatment. This fracture was reported to have an incidence of 0.86% (13 fractures) out of 1,500 ankle injuries2 and subsequently to comprise 24% of all talar body fractures.10 Hawkins described it as the second most common fracture of the talus,1 with other reports of it comprising 33-41% of talar fractures overall.2,9,11 Relative to overall ankle injuries sustained by snowboarders, Pigozzi12 found that 8% involved lateral process fractures, while Bladin and McRory5 as well as Kirkpatrick et al7 reported 15%. It has also been noted to comprise 34% of ankle fractures in snowboarders.7 Thus, this fracture has a 15-fold greater rate in snowboarders than in the general population. ANATOMY