Kinematic analysis of the movement of thyroid cartilage and hyoid bone during swallowing

Abstract

The movement of hyoid bone has been reported to be related in diagnosing dysphagia. In clinical setting, it could be evaluated by video fluoroscopic swallowing study (VFSS) that induces radiation exposure. In contrast with hyoid bone, the thyroid cartilage is easily seen through anterior neck. We hypotheses that the movement of thyroid cartilage correlates with that of hyoid bone and can be used as a parameter for swallowing evaluation. The purpose of this study is to investigate if the movement of thyroid cartilage and hyoid bone is correlated and to collect basic data for using thyroid cartilage as a parameter for swallowing evaluation. Total 25 subjects’ VFSS images with normal swallowing function were analyzed by specially developed software. Positions of laryngeal prominence and margin of the hyoid were automatically extracted. Two sets of the loci were obtained in all frames of VFSS. X- and Y-coordinates showed anterior-posterior axis and superior-inferior axis. Pearson correlation coefficients for X- and Y-coordinate components were computed respectively. X- and Y-coordinates of thyroid cartilage and hyoid bone moved in a similar pattern. Pearson correlation coefficient of X- and Y-coordinate components was from 0.611 to 0.981, which meant movement of thyroid cartilage and that of hyoid bone was strongly correlated. We could analyze the movement of thyroid cartilage and hyoid bone by specially developed software and concluded that the movement of thyroid cartilage and hyoid bone was strongly correlated. This study implies that analysis of thyroid cartilage can be used as a parameter for swallowing evaluation.