Incidence and anatomical variability of accessory and sesamoid bones of the foot

Aim: We aimed to assess the incidence, mean size, patterns, and types of accessory and sesamoid bones of the foot using computed tomography. Material and Methods: A total of 814 non-contrast-enhanced computed tomography images of the foot obtained from 717 patients between October 2015 and January 2018 were investigated retrospectively. Images acquired in the original axial plane were used to perform multiplanar reconstruction in the coronal or sagittal planes. Incidence, mean size, patterns, and types of accessory and sesamoid bones were evaluated in all images. Results: Accessory bones were detected in 387 (47.5%) non-contrast-enhanced computed tomography scans from 326 patients (45.4%). Sixty-seven patients (9.3%) showed accessory bones on both sides; 133 patients (18.5%), only on the right side; and 126 patients (17.5%), only on the left side. The most common accessory bones of the foot were the os naviculare accessorium (24.8%), os trigonum, (20.3%), os peroneum (14.6%), os intermetatarseum (10.6%), os supranaviculare (3.1%), os supratalare (1.9%), and os vesalianum (1.5%). The hallucal sesamoid bone was observed in all patients, while the interphalangeal sesamoid bone was observed in 34.6% of the patients. Conclusions: The computed tomography scans provided a detailed overview of the characteristics of accessory and sesamoid bones, and the incidence of these bones in our patients was higher than those reported in previous radiographic studies. Our findings can facilitate the diagnosis and management of disorders involving these bones.