Causes / typical injury mechanism: A lateral talar process fracture (LTPF) is an uncommon fracture pattern seen most commonly in snowboarders; it is colloquially termed the "snowboarder's fracture." The lateral process of the talus is a wedge-shaped prominence off the lateral aspect of the talus. It articulates with the fibula dorsolaterally and contributes to maintenance of the ankle mortise and lateral ankle stabilization. It also serves as the origin of the lateral talocalcaneal ligament and articulates with the posterior facet of the calcaneus to contribute to the subtalar joint.

Although the mechanism of injury for LTPFs was originally described as axial loading and forced dorsiflexion on an inverted foot, others now believe eversion and external rotation play a larger role than inversion. Resultant fractures can range from small avulsions to large, displaced, and comminuted fractures.

Classic history and presentation: The symptoms of LTPFs are vague lateral ankle pain and swelling in the sinus tarsi, just anterior and distal to the tip of the lateral malleolus. The pain resembles that of an ankle sprain, causing LTPFs to be missed in up to 59% of cases.

Prevalence: Fractures of the talus account for less than 1% of all fractures, with LTPFs accounting for approximately 20% of talar fractures. LTPFs are 17 times more common in snowboarders than nonsnowboarders. They account for 2.3% of all snowboarding injuries and up to 34% of all fractures involving the ankle in snowboarders. LTPFs can occur in patients of all ages.

Risk factors: A major risk factor for LTPFs is snowboarding. Other sporting activities with higher prevalence include football and rugby. It is important to note that LTPFs do not occur solely during these activities but are also seen after rotational ankle injuries involving a variety of activities.

Associated conditions include:

• Peroneal tendon tears
• Peroneal tendon dislocation / subluxation
• Ipsilateral talar body / neck fractures
• Ipsilateral calcaneus fractures
• Intraarticular loose bodies
• Osteochondral defects (the posterolateral calcaneal facet and the plantolateral aspect of the talar head are the most common)
• Talocalcaneal ligament disruption

Grade / classification system: Many classification systems exist, but the first and most widely recognized is the Hawkins classification:

• Type I: Simple fractures – Extend from talofibular articulation to the posterior talocalcaneal articulation.
• Type II: Comminuted fractures – Involve both the fibular and calcaneal posterior process articular surfaces.
• Type III: Chip fractures – Involve the anterior and inferior aspect of the posterior articular process of the talus with the calcaneus; do not involve the talofibular articulation.