Hyoid bone position and upper airway patency: A computational finite element modeling study

Background and Objectives: The hyoid bone's inferior baseline position in obstructive sleep apnea (OSA) has led to surgical hyoid repositioning treatment, yet outcomes vary widely. The influence of baseline hyoid position (phenotype) and surgical hyoid repositioning on upper airway function remains unclear. We aimed to investigate their impact on the upper airway using computational modeling. Methods: A validated finite element model of the rabbit upper airway was advanced and used to simulate changes in baseline hyoid position and surgical hyoid repositioning, alone and in combination. The hyoid was displaced in cranial, caudal, anterior, anterior-cranial and anterior-caudal directions from 1-4mm. Model outcomes included upper airway collapsibility, measured using closing pressure (Pclose), cross-sectional area (CSA) and soft tissue mechanics (stress and strain). Results: Graded baseline hyoid position increments increased Pclose for all directions, and up to 29-43% at 4mm (relative to the original baseline hyoid position). Anterior-based surgical hyoid repositioning decreased Pclose (~-115% at 4mm) and increased ΔCSA (~+35% at 4mm). Cranial surgical hyoid repositioning decreased ΔPclose (-29%), minimally affecting CSA. Caudal surgical hyoid repositioning increased ΔPclose (+27%) and decreased ΔCSA (-7%). Anterior-cranial and anterior-caudal surgical hyoid repositioning produced the highest stresses and strains. Surgical hyoid repositioning effects on upper airway outcomes were dependent on baseline hyoid position, with more caudal baseline hyoid positions leading to less effective surgeries. Conclusions: Baseline hyoid position (phenotype) and surgical hyoid repositioning both alter upper airway outcomes, with effects dependent on hyoid displacement direction and magnitude. Baseline hyoid position influences the effectiveness of surgical hyoid repositioning in reducing upper airway collapsibility. These findings provide further insights into the hyoid's role in upper airway patency and suggest that considering the hyoid's baseline position and surgical repositioning direction/increment may help improve hyoid surgeries for OSA treatment.