Influence of craniofacial morphology on hyoid movement: a preliminary correlational study.

There has been little attention given to the relationship between variations in normal craniofacial morphology and swallowing physiology. This preliminary investigation evaluated the relationship between the Frankfort-mandibular plane angle (FMA) and hyoid displacement during swallowing. Hyoid movement was evaluated during 12-ml and 24-ml swallows of liquid barium in 12 healthy subjects (age = 20-29 years, median = 23 years). Lateral projection videofluorography was utilized. Positions of the hyoid at maximum forward displacement, maximum upward displacement, starting position, and ending position were determined using image analysis software. The mean FMA was 28.92 degrees +/- 4.08 degrees (mean +/- SD, range = 20 degrees -34 degrees ). A Pearson correlation (<or=0.05) demonstrated that hyoid forward displacement was significantly inversely correlated with the FMA [R = -0.68, p = 0.015 (12 ml) and R = -0.72, p = 0.009 (24 ml)]; thus, the greater the FMA, the smaller the hyoid forward displacement. Upward displacement of the hyoid was not significantly correlated with FMA for 12-ml (R = -0.41, p = 0.55) or 24-ml swallows (R = 0.21, p = 0.512). In addition, there was no significant correlation between hyoid starting or ending positions. In conclusion, the results of this preliminary study suggest that normal variations in morphology, as measured by the FMA, may influence hyoid movement and therefore affect swallowing physiology.