Hyoid bone position in subjects with different vertical jaw dysplasias

To test the hypothesis that there is no difference in hyoid bone position among subjects with different vertical jaw dysplasias.

Seventy-one North Indian adult male and female subjects in the age range of 15 to 25 years were selected for the study. Based on the vertical growth pattern of the face, subjects were divided into Group I (n = 24; subjects in whom both Frankfort mandibular plane angle [FMA] and basal plane angle measured 20 to 25 degrees), Group II (n = 17; subjects in whom both FMA and basal plane angle measured <15 degrees), and Group III (n = 30; subjects in whom both FMA and basal plane angle measured >30 degrees). Lateral cephalograms with the mandible in rest position were traced and analyzed manually for evaluation of hyoid bone position.

The anteroposterior position of the hyoid bone was significantly forward in subjects with short face syndrome compared with normal subjects (P < .05) and subjects with long face syndrome (P < .001). The vertical position of the hyoid bone was comparable among subjects with different vertical jaw dysplasias. The axial inclination of the hyoid bone was more oblique in subjects with long face syndrome than in those with short face syndrome (P < .01).

The anteroposterior position of the hyoid bone was more forward in subjects with short face syndrome. The vertical position of the hyoid bone was comparable among subjects with different vertical jaw dysplasias. The axial inclination of the hyoid bone closely followed the axial inclination of the mandible.