Relationship between morphological characteristics of hyoid bone and mandible in Japanese cadavers using three-dimensional computed tomography.

The aim of this study is to obtain a quantitative anatomical description of the hyoid bone and mandible using three-dimensional computed tomography. Hyoid bones were obtained from a total of 101 cadavers varying in age from 67 to 102 years. The percentage of symmetrical U-type and asymmetrical-type hyoid bones was low compared with symmetrical V type (14.9, 15.8, and 69.3 %, respectively), and no significant sex difference was observed. We found bilateral nonfusion in cadavers of advanced age at a rate of 22.7 % and bilateral complete fusion at a rate of 51.5 %. There were significant differences in metric variables (length and width) between males and females, but no significant differences in width among the different fusion types. There was no significant interaction effect of sex and degree of fusion. Strong significant associations were observed between size (length and width) of the hyoid bone and mandible in the nonfusion group, while the complete fusion group revealed a moderate correlation. We also investigated the hypothesis that the junction between the hyoid body and greater horn plays an important role in the movement of bones that have not yet ossified. However, no statistical difference was observed in the width between the two greater horns. The degree of fusion of the greater horn with the hyoid body may also affect relations of interdependencies between the hyoid bone and mandible, an important component to consider when assessing risk factors in the development of masticatory and swallowing function.