The Accessory Ossicles of the Foot and Ankle; a Diagnostic Pitfall in Emergency Department in Context of Foot and Ankle Trauma

Abstract

Trauma of the foot and ankle is commonly seen in patients presenting to accident and emergency departments (1). Although, the use of Ottawa Ankle Rules has reduced unnecessary radiographs, radiography still remains the most appropriate initial imaging modality in patients with suspected fractures (2). The decision to engage in further imaging, indications for conservative treatment versus surgery and consultation with an orthopedic surgeon or radiologist, often rests on the emergency physician’s interpretation of the radiographical findings. Therefore, it is important for the emergency physician to be aware of abnormal and normal variants of bony lesions of the foot and ankle and the various radiological pitfalls that may cause confusion. Many skeletal variations of the foot and ankle are found, including different accessory ossicles and sesamoid bones. Sesamoid bone is a small rounded bone embedded within a tendon or joint capsule. Sesamoid bones are typically found in locations where a tendon passes over a joint. They prevent the friction between the tendon and the joint, protect the tendon and increase its biomechanical effect by changing the direction of pull of the tendon. On the other hand, accessory ossicles are usually derived from the failure of union of secondary ossification centers to the main bony mass. They usually remain asymptomatic and are recognized as an incidental radiographic finding (3). However, in the context of trauma, these ossicles can be misdiagnosed as avulsion fractures, or a reverse situation in which an avulsion fracture can be evaluated as an accessory ossicle is possible. This pictorial review summarizes the most common accessory ossicles found around the foot and ankle and the fractures that may cause confusion with the accessory ossicles and sesamoid bones Abstract