Calcaneal Fracture - Anatomy and Classification

Anatomy and Classification

The calcaneus, also known as the heel bone, is the largest of the tarsal bones and articulates with the cuboid bone anteriorly and the talus bone superiorly. It is responsible for transmitting the majority of the body's weight from the talus bone to the ground.

Calcaneal fractures are categorized into two types: Intra- and Extrarticular fractures on the basis of subtalar joint involvement. Intrarticular fractures are more common and involve the posterior talar articular facet of the calcaneus. The Sanders system classifies these fractures into four types, based on the location of the fracture at the posterior articular surface. Extrarticular fractures are less common, and located anywhere outside the subtalar joint. Extrarticular fractures are categorized depending on whether the involvement of the calcaneus is anterior (Type A), Middle (Type B) or Posterior (Type C).

The Angle of Gissane, or "Critical Angle", is the angle formed by the downward and upward slopes of the calcaneal superior surface. On a lateral radiograph, an angle of Gissane of > 130° suggests fracture of the posterior subtalar joint surface. The Böhler's angle, or "Tuber Angle", is another normal anatomic landmark seen in lateral radiographs. It is formed by the intersection of 1) a line from the highest point of the posterior articular facet to the highest point of the posterior tuberosity, and 2) a line from the former to the highest point on the anterior articular facet. An angle < 20° suggests a depression of posterior facet and possible calcaneal fracture.