Examination of the accessory bones in the foot with computed tomography

Introduction and Purpose: Sesamoid bones are bone structures that are partially or completely embedded in a tendon. Their function is to protect the tendon from injury by reducing friction. In contrast, accessory bones are bones that are usually made up of unfused primary or secondary ossification centers. They are thought to be developmental anomalies with no known definite function. These bones can become infected and dislocalized as a result of painful fractures in the foot; In addition to these, they are important because they can be confused with avulsion fractures. From this point of view, in this study; We aimed to determine the frequency and morphometric properties of sesamoid and accessory bones. Material-Methods: A total of 400 different foot images, 187 right feet and 213 left feet, of 239 males and 161 females over the age of 18 (min. 18, max. 86) who underwent foot CT scans for various reasons between 2022 and 2024 at the Department of Radiology, Faculty of Medicine, Selçuk University, were retrospectively examined. The frequency and morphometry (long diameter-short diameter and surface area measurement) of the accessory and sesamoid bones in the foot in sagittal, coronal and axial planes were examined and statistical analysis was performed according to gender, age and side (right-left). Results: In our study, at least one accessory bone was detected in 270 (67.5%) of 400 feet. 2.75% of the detected accessory bones were bipartite accessory bones. The most common accessory bones were determined as 41.5% os naviculare accoria, 14% os trigonum, and 13% os peroneum. In our study, an accessory bone was detected in the plantar part of the tarsometatarsea lateralis art. between os cuboideum and os metatarsale IV, which has not been previously described in the literature. The reason for its location was called cubo-metatarsale IV plantare. In our study, hallux sesamoids (medial and lateral) were detected in 100%, while the bipartite rate was observed as 7%. All measurement values of sesamoid bones were found to be significantly larger in male individuals than in female individuals (p<0,05). In the comparison between age ranges of hallux sesamoids, the measurement values that could be performed in individuals aged 60 years and above were significantly greater than those between the ages of 18-29 (p<0,05). Conclusion: It was found that the size of the sesamoid bones and the number of accessory bones increased in older age groups and that the hallux sesamoids of male individuals were larger than those of female individuals. We believe that our study contributes to the literature with the morphometric data obtained and the accessory bone discovered and will also guide clinicians in the diagnosis of related foot pathologies. Keywords: Accessory bones, foot, computed tomography, sesamoid bones.