Assessment of the Morphology and Frequency of Hyoid Bone Fusion and its Relationship with Age and Sex on CBCT Images

Hyoid bone is a solitary bone, which is composed of a main body and two pairs of horns (greater, and lesser). This bone has an important function in respiration, swallowing, and speech. This study aimed to define the morphology and the frequency of fusion of hyoid bone and its relationship with age and sex on CBCT images.

In this cross-sectional descriptive analytical study, the CBCT images of 163 patients (92 females and 71 males) were analyzed using Type I OnDemand 3D software. In the axial cross-sections, the thickness and length of the hyoid body was measured; in coronal cross-sections, hyoid bone height was measured; and on the thick axial crosssections, the angle between the hyoid bone greater horn and the hyoid bone body midline was measured. The body and greater horn were classified into four categories in terms of fusion (non-fusion with a distance > 2.5 mm, non-fusion with a distance < 2.5 mm, partial fusion and complete fusion). The data were analyzed with Kolmogorov-Smirnov, chi-squared, and Fisher’s exact tests, paired t-test, and Kruskal-Wallis nonparametric test using SPSS 25 (α = 0.05).

In 79.7% of the patients the fusion was similar on both sides (p value = 0.806). There was no significant difference in hyoid bone fusion morphology between male and female groups and between the two sides (p value = 0.977). The most and least frequent types of hyoid bone fusion were type II (non-fusion with a distance < 2.5 mm) and type III (partial fusion), respectively. With the exception of the 10-19 year age group, type II category was the most common type, while type I was the most common in the 1–19-year age group. Hyoid bone fusion morphology varied significantly between the different age groups (p value < 0.05). Hyoid bone size (thickness, length, and height) was greater in men compared to women (p value < 0.05); however, the angle exhibited no significant difference between the male and female subjects (p value = 0.591). Of all the hyoid bone dimensions, only the length of its body was significantly different between the different age groups (p value < 0.05).

With advancing age, the distance between the body and the greater horn of the hyoid bone decreased, and its fusion frequency increased. Only the hyoid body length was different between the different age groups, and the other hyoid bone dimensions were the same. All the hyoid bone dimensions were greater in men compared to women, with the exception of the angle. It is possible to differentiate males from females based on the above-mentioned parameters. CBCT can help reconstruct the hyoid bone using its multiplanar reconstruction with lower radiation.