Computational simulations of hyoid bone position and tracheal displacement: effects on upper airway patency and tissue mechanics

Surgical hyoid repositioning (HR) improves upper airway (UA) patency. Tracheal displacement (TD) likely influences HR outcomes, and vice versa, due to hyoid-trachea connections. This study used computational modeling to investigate the influence of TD and HR (with fixation) on UA outcomes and the impact of a lower baseline hyoid position [obstructive sleep apnea (OSA) phenotype]. A two-dimensional (2-D) finite element model of the rabbit UA simulated TD and HR (with fixation) 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. Compared with baseline (TD = HR = 0 mm), 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%). Combined TD and HR (except caudal) improved UA outcomes beyond either intervention applied alone. A more caudal baseline hyoid position reduced these effects. This computational model of the rabbit upper airway suggests that optimizing OSA treatment outcomes could involve considering baseline hyoid position, degree of TD, and direction/extent of HR, with potential benefits from combining HR and TD-based approaches.<b>NEW & NOTEWORTHY</b> Computational simulations of the rabbit upper airway suggest that combining tracheal displacement with anterior-based hyoid repositioning, with fixation, improves airway outcomes more than either approach alone. However, a lower natural hyoid position, characteristic of obstructive sleep apnea (OSA), reduces these benefits. Optimizing OSA treatment may require considering the natural hyoid position, surgical hyoid repositioning direction/magnitude, and natural tracheal displacement range. A combined tracheal displacement-hyoid repositioning strategy may further improve airway patency in select cases.