The incidence of accessory navicular bone types in Turkish subjects

Accessory ossicles are the skeletal variations of the ankle and foot that can cause painful syndromes. The accessory navicular bone is one of the most common accessory ossicle of the foot (4-21%) and is also known as os tibiale, os tibiale externum and os naviculare secundarium. This bone can be adjacent to the posteromedial tuberosity of the navicular bone or can be separated and may cause various diseases in the foot and mimic fractures of foot bones. The aim of this study was to document a detailed investigation of incidence and types of accessory navicular bones of Turkish subjects according to sex in both extremities. The accessory navicular bone was detected (11%) via the posterior-anterior radiographs of 650 subjects in the radiological examination. The incidences of accessory navicular bones were identified as 6.1-4.9% in female and male participants. Accessory navicular bones were classified into three groups as Type I, Type II and Type III and the incidences of these bones were determined as 3.3, 3.1, 4.6%, respectively. Each group was also divided into subgroups. The incidences of the subgroups are as Type Ia 0.6%, Type Ib 1.5%, Type Ic 1.2%, Type IIA/a 0.8%, Type IIA/b 0.4%, Type IIA/c 0%, Type IIB/a 1.1%, IIB/b 0.3%, IIB/c 0.5%, Type IIIa 1.5%, Type IIIb 1.4%, Type IIIc 1.7%. Finally, the types of accessory navicular bones were discussed and the imaging modalities for diagnosis were presented.