Classic history and presentation: Due to the differences in types of calcaneal fractures and mechanisms of injury described below, patients may present in a variety of ways. A patient with calcaneal fracture will typically complain of pain in the hind foot that makes weight-bearing difficult or impossible. However, severity of soft tissue involvement and fracture displacement is proportional to the amount of trauma and force leading to the injury. Low-energy injuries may only be associated with mild to moderate pain, swelling, or ecchymosis. High-energy injuries such as a fall from a height or a motor vehicle accident may present with significant pain, bruising, or even open fractures. Additionally, patients may present with compartment syndrome or fracture blisters.
Prevalence: This injury typically involves young, active, working men, with peak incidence at the ages of 20-29 years. While the incidence in men decreases after age 60, the incidence in women increases after age 50 and is associated with osteoporotic bones secondary to low-energy falls.
Pathophysiology: The anatomy of the calcaneus and its surrounding structures is complex, and a thorough understanding is important for classification and management of a fracture. The calcaneus has 4 articulations that are integral for weight-bearing. At the distal end of the anterior process, the calcaneus articulates with the cuboid to form the calcaneocuboid joint. Superiorly, the calcaneus has 3 facets, the anterior, middle, and posterior, which articulate with the talus to form the subtalar joint. The posterior facet is the largest of the 3 and is the primary load-bearing component of the subtalar joint. The sustentaculum tali is a dense projection of cortical bone that protrudes from the medial aspect of the calcaneus, which supports the middle facet and articulates with the neck of the talus. Additionally, the calcaneal tuberosity sits posterolaterally, to which the Achilles tendon inserts itself into posterior inferior aspect of the tuberosity.
Extraarticular fractures, defined by not involving the subtalar joint, represent about 25% of all calcaneal fractures. These can be caused by avulsions of the anterior process, the sustentaculum tali, or the calcaneal tuberosity. Fracture of the anterior process can occur secondary to sudden inversion of a plantarflexed ankle, leading to avulsion at the insertion of the bifurcate ligament. Calcaneal tuberosity fractures most commonly occur as the result of a forceful contraction of the gastrocnemius-soleus complex, with forced dorsiflexion. Generally, this can be seen in association with a low-energy fall, often in an osteoporotic patient.
Historically, up to 75% of calcaneus fractures are intraarticular, which refers to the extension of the fracture line into the subtalar joint. Typically, this injury is the result of a significant axial load being transferred through the talus into the calcaneus, usually following a fall from significant height or a motor vehicle accident. The exact fracture pattern is determined by many variables including the force of impact and the position of the hindfoot at the time of injury. A primary fracture line develops as the result of a shear force when the overlying talus is driven through the posterior facet, creating a superolateral fragment and a superomedial or "constant fragment," which remains attached to the talus via the deltoid ligamentous complex. Additional secondary fracture lines, described by Essex-Lopresti, can also develop with increased force. If the secondary fracture line propagates back to the posterior border of the tuberosity, it is termed tongue type. However, if the secondary fracture line exits superiorly and directly posterior to the posterior facet, it is termed joint depression type.
Grade / classification system: The Essex-Lopresti classification system relies solely on plain radiographs and divides intraarticular calcaneal fractures into 2 types based on the secondary fracture line. If the secondary fracture line propagates back to the posterior border of the tuberosity, it is termed tongue type. However, if the secondary fracture line exits superiorly and directly posterior to the posterior facet, it is termed joint depression type. The simplicity of this classification system can make it useful in the emergency department (ED) when acutely managing a calcaneal fracture, as tongue-type fractures have been associated with soft tissue injury and posterior skin breakdown.
The Sanders classification system is widely utilized and is based on coronal CT images. It considers the number and location of fracture lines that enter the posterior facet. It should be noted that, while this classification system was developed to guide treatment and management, its reliability has been questioned because of low intra- and interobserver reproducibility. The Sanders intraarticular classification is –
- Sanders I: Undisplaced fractures, regardless of number of fracture lines.
- Sanders II: 1 fracture line; 2 main posterior facet fragments.
- Sanders III: 2 fracture lines; 3 main posterior facet fragments; central fragment depressed / rotated.
- Sanders IV: 3 or more fracture lines; 4 or more main posterior facet fragments.