Computational Simulations of Hyoid Bone Position and Tracheal Displacement: Effects on Upper Airway Patency and Tissue Mechanics

ABSTRACT Surgical hyoid repositioning (HR) improves upper airway (UA) patency. Tracheal displacement (TD) is likely to impact HR outcomes, and vice versa, due to hyoid-trachea connections. This study used computational modeling to investigate the influence of TD and HR on UA outcomes and examine the impact of a more caudal baseline hyoid position (OSA phenotype). Methods A 2D finite element model of the rabbit UA was used to simulate TD and HR (in different directions), separately and combined. Model outcomes included UA closing pressure (Pclose), area, anteroposterior diameter (APD) and soft tissue mechanics (stress/strain). Simulations were repeated with a more caudal baseline hyoid position. Results Compared to baseline (TD=HR=0mm), TD alone reduced Pclose by −34%, increased area by 21% and APD by up to 18%. HR alone (except caudal) improved outcomes, particularly anterior-cranial HR which decreased Pclose by −106%, increased area by 32% and APD by up to 107%. TD+HR (except caudal) enhanced these outcomes, with TD+anterior-cranial HR further decreasing Pclose (−131%) and increasing area (55%) and APD (128%). A more caudal baseline hyoid position reduced the effect of TD+anterior-cranial HR on Pclose (−43%), area (49%) and APD (115%). Conclusion The combination of TD and HR (except caudal) improved UA outcomes even further than when either intervention was applied alone. A more caudal baseline hyoid position reduced the overall impact of each intervention. This study suggests that considering the baseline hyoid position, the degree of TD, and the extent/direction of surgical HR could be crucial in optimizing OSA treatment outcomes. Key points summary Surgical hyoid repositioning can improve upper airway patency and is a treatment for obstructive sleep apnea (OSA). Tracheal displacement, also critical to upper airway function, likely influences hyoid repositioning outcomes due to hyoid-trachea connections. This study used a computational model of the upper airway to simulate tracheal displacement and hyoid repositioning in various directions and magnitude, assessing their impact on upper airway collapsibility, size, and soft tissue mechanics. The influence of a more caudal baseline hyoid position, like in OSA, was also simulated. Combining tracheal displacement with anterior-based hyoid repositioning, in particular, resulted in greater improvements in upper airway outcomes compared to tracheal displacement and hyoid repositioning alone. A more caudal baseline hyoid position diminished the upper airway improvements with both interventions Optimizing OSA treatment outcomes with hyoid surgeries may require considering the baseline hyoid position, the degree of tracheal displacement, and the direction/magnitude of surgical hyoid repositioning.