Wheeless' Textbook of Orthopaedics Mechanism and pathoanatomy of the intraarticular calcaneal fracture. The mechanism and pathoanatomy of the acute intraarticular calcaneal fracture is produced by axial loading. A combination of shear and compression forces produce two characteristic primary fracture lines. Shearing forces produce a fracture dividing the calcaneus into medial and lateral portions. This fracture line typically splits the posterior facet and can extend anteriorly to involve the anterior and cuboid facets.
Compression forces divide the calcaneus into anterior and posterior portions.
This fracture line can extend medially to involve the middle facet. Loss of calcaneal height and length are readily explained by this mechanism.