Evaluating the Structural Properties of Suprahyoid Muscles and their Potential for Moving the Hyoid

Superior and anterior hyoid movements are important events in pharyngeal deglutition. This cross-sectional study uses a cadaver model to document the structural properties of the muscles underlying these movements in an effort to understand how their morphology influences function. Measurements to determine physiological cross-sectional areas (PCSAs) of swallowing muscles were taken from hemisected head and neck formalin-fixed cadaver specimens (n = 13). Coordinates of muscle attachment sites and PCSAs were used to calculate (i) over cap and (j) over cap unit force vectors, where (i) over cap and (j) over cap represent anterior-posterior and superior-inferior directions, respectively. The suprahyoid muscle subsamples were grouped for analysis as follows: digastric (DG), geniohyoid (GH), mylohyoid (MH), and stylohyoid (SH). The ANOVA with Tukey HSD post hoc analysis of unit force vectors showed the following results: GH (-0.44 +/- 0.15 cm(2)) [MH (-0.02 +/- 0.21 cm(2)), DG (-0.05 +/- 0.11 cm(2)), SH (0.14 +/- 0.04 cm(2)), with negative values representing the anterior direction (p < 0.01); and MH (0.91 +/- 0.28 cm(2)) [DG (0.29 +/- 0.14 cm(2)), SH (0.22 +/- 0.08 cm(2)), GH (12 +/- 0.08 cm(2)), with positive values representing the superior direction (p < 0.01). The morphology of the suprahyoid muscles suggests that based on structural properties, the geniohyoid has the most potential to displace the hyoid in the anterior direction and the mylohyoid has the most potential to displace the hyoid in the superior direction. These data in complement with physiological findings may provide greater insight into these movements for those developing novel treatments for dysphagia.