The shape and size of the human hyoid bone and a proposal for an alternative classification.

Human hyoid bones, according to the main characteristics of their shape, studied in 76 bones, may be classified into five types, in the following order of frequency:D-type 29%, B-type 26.5%, H-type 21%, U-type 18.5%, and V-type 5.0%. The frequency of the types is to a certain (but not statistically significant) degree sex-related. In 60% of the cases the shape of the hyoid bone does not belong to any of the shapes that are conventionally described. Almost half of the hyoid bones are asymmetric and/or anisometric. According to their width the hyoid bones may be designated as narrow (45%), intermediate (34%) and wide (21%). There is no standard correlation of the distance between the tubercles of the greater horns to the distance between the lesser horns in the same hyoid bone. On the contrary, with the exception of the horseshoe-shaped bones, the former distance almost coincides to the length of the major transverse axis of the same bone. The two dimensional size of the hyoid bone, which is of importance to the vital space of the superior opening of the lower respiratory tract, varies greatly, and to a certain degree it is related to the hyoid shape.