Anterior calcaneal process fractures are the result of an inversion and plantarflexion injury. It represents an avulsion fracture of the bifurcate ligament. The fracture is classified as an extra-articular calcaneal fracture (does not involve subtalar joint) but can extend to the calcaneocuboid joint. 

This diagnosis can be challenging on plain x-rays, and the anterior calcaneal process should be a check area on foot x-rays, especially in exams!