Anterosuperior Calcaneal Process Fracture or OS Calcaneus Secundarius?

Abstract

A 36-yr-old woman was admitted to our emergency department after having sustained an inversion injury of her right ankle. On physical examination, there was diffuse swelling and ecchymosis on the dorsolateral aspect of her foot. The ankle joint movements were in normal range without laxity. The anteroposterior and lateral x-rays of the right foot were considered to be normal by the emergency physician. The patient was diagnosed with simple ankle sprain and was treated accordingly with classical RICE protocol and a nonsteroidal antiinflammatory drug. Four weeks after the initial trauma, the patient presented to our orthopedic outpatient clinic with persistent complaint of right foot pain on weight bearing. On physical examination, severe pain on the dorsal part of the calcaneocuboid joint was present. The initial anteroposterior and lateral x-rays were reevaluated, and a fracture was suspected at the anterior calcaneal process (Fig. 1A). Medial oblique foot x-ray revealed a bony fragment located between the anterosuperior calcaneal process and the cuboid (Fig. 1B). In the differential diagnosis, anterosuperior calcaneal process fracture and OS calcaneus secundarius were considered. Further computed tomography imaging delineated the anatomy of the fragment better, while the ovoid shape, well corticated margins, regular interface, and blunt edges of the fragment supported the diagnosis of OS calcaneus secundarius, wide proximal base and considerably large size favored the anterosuperior calcaneal process fracture. Magnetic resonance imaging was eventually performed and, with the presence of bone marrow edema adjacent to the fracture line, an anterosuperior calcaneal process fracture rather than an OS calcaneus secundarius was confirmed at diagnosis (Fig. 2). She was treated with a medial longitudinal arc support, and after 1 mo, she was free of pain during mobilization.FIGURE 1: A, Medial oblique x-ray of the right foot demonstrating a suspective diagnosis of either OS calcaneus secundarius or an anterosuperior calcaneal process (ASCP) fracture (upper left). B, Computed tomography of the patient demonstrating the lesion with a wide proximal base (upper right).FIGURE 2: Magnetic resonance imaging demonstrating the bone marrow edema (bottom).OS calcaneus secundarius and anterosuperior calcaneal process fractures are two similar clinical syndromes, both of which present with anterior ankle pain.1 The differentiation of these two entities may be quite challenging only with physical examination or classical x-rays.2 Herewith, we imply that the distinction may be possible when oblique x-rays or, even better, magnetic resonance imaging is performed.3 This is important because the treatment of each syndrome is different.