Anterior calcaneal process fractures are often missed fractures of the calcaneus (up to 88% are not reported on radiographic examination of the ankle) 1 leading to non-union of bone fragments, unrecognised associated ligamentous injuries, and persistent ankle or foot pain.
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Epidemiology
Anterior process fractures are a relatively rare occurrence, accounting for only 3% of calcaneal fractures 2.
Associations
They are generally not isolated but occur in association with the following:
Diagnosis
Plain radiography remains the primary imaging modality for assessing calcaneal trauma because the fractures of the anterior process of the calcaneus occur in precise locations with characteristic radiographic features 3.
Clinical presentation
Symptoms include nonspecific lateral ankle pain.
Pathology
Two mechanisms for anterior calcaneal process fractures have been described 3:
the commonly recognized mechanism is an injury by flexion, inversion, and distraction of the bifurcate ligament leading to an avulsion fracture of variable size from the anterior calcaneal process
infrequently, impaction by eversion and dorsiflexion of the midfoot (known as the nutcracker mechanism) is observed
Classification
The classification by Degan et al. 4 is the most commonly used (c. 2019) but criticisms include that location (i.e. medial, central, lateral) and fracture extent are not included 6. Three types are described:
type I: non-displaced avulsion fractures with no calcaneocuboid joint involvement
type II: displaced fractures with no calcaneocuboid joint involvement
type III: displaced fractures with calcaneocuboid joint involvement
Treatment and prognosis
There are no specific guidelines for the management of these injuries due to the rarity of its presentation. Typically, type I and type II fractures can be managed with plaster cast immobilization with surgery intended for symptomatic patients only; conversely, type III fractures are managed with open reduction - internal fixation (ORIF) as they have a higher rate of malunion/non-union 4.
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