Three-Dimensional CT Findings of Os Calcaneus Secundarius Mimicking a Fracture

Abstract

Os calcaneus secundarius is one of several accessory ossicles of the foot that have been identified as normal variants of skeletal development. It may cause ankle pain and may mimic an avulsion fracture of the anterior calcaneal process. A twenty-year-old male was admitted to our institution with right ankle pain following an inversion injury. An axial CT image of the patient's right ankle revealed a shape with smooth and sharp margins, identified as a well-corticated bone fragment in the subtalar region. A diagnosis of an accessory ossicle, os calcaneus secundarius, was made based on radiographic findings. As a result of this case, it is recommended that potential locations of the accessory bones should be well understood in order to prevent misdiagnosis and inappropriate surgical procedures. Os calcaneus secundarius must be considered when an apparent bone fragment or a suspicious fracture line at the anterior region of os calcaneus is demonstrated.

A case of an injured calcaneus secundarius in a professional soccer player

“…To date, only a few cases of symptomatic CS have been published, mostly in the setting of chronic ankle pain [ 4 – 7 ]. To our knowledge, no such presentation of an acutely injured large CS has been reported.…”

“…To our knowledge, no such presentation of an acutely injured large CS has been reported. The diagnosis of symptomatic CS can be challenging for emergency physicians because this accessory bone can easily be mistaken for a fracture of the anterior process or the tuberosity of the calcaneus [ 3 , 4 ]. Moreover, it has to be differentiated from other accessory ossicles, such as a calcaneus accessorius, cuboideum secundarium, and os sustentaculi [ 1 ].…”

“…The CS is generally bridged to the calcaneus by poorly mobile synchondrosis. This accessory bone can be frequently mistaken for a fracture of the anterior process of the calcaneus in foot injuries or in persistent chronic ankle pain [ 3 , 4 ]. Computed tomography (CT) or magnetic resonance imaging (MRI) might be indicated to assess the diagnosis.…”

Anatomical variation in the ankle and foot: from incidental finding to inductor of pathology. Part I: ankle and hindfoot

“…If one of these fractures is suspected, CT or MRI should be performed to fully characterise, given the implications for treatment [21] (Fig. 7).…”

“…Just as with the previously seen ossicles, the diagnosis can be established with the clinical background, and the typical irregularity of margins of fracture and no cortication described [22]. The presence of oedema on MRI confirms the presence of acute fracture [21]. Lack of clinical symptoms and history of trauma and lack of a donor site in the calcaneus are two important features that would suggest the presence of a calcaneus secundarius [23].…”