Mechanical interactions between airway stents and the airway wall: biomechanics, complications, and design optimization

Abstract Airway stents are indispensable tools for managing central airway stenosis, tracheomalacia, and tracheoesophageal fistula. However, their long-term clinical efficacy remains bottlenecked by recurrent complications, including migration, granulation tissue hyperplasia, structural fracture, mucus retention, and localized infection. Mounting clinical and biomechanical evidence suggests that mechanical mismatch between the stent and the host airway may contribute to these adverse events. In this narrative review, we examine airway stents through the critical lens of stent-tissue mechanical interaction. We first delineate the foundational biomechanical properties governing stent behavior within the respiratory tract: radial force, flexibility, fatigue resistance, and airway fluid dynamics. Crucially, we examine the potential links between discrepancies in these mechanical traits and clinical complications, focusing on inadequate support versus excessive local tissue stress, failed adaptation to dynamic airway deformation, fatigue-induced structural failure under cyclic respiratory loading, and incomplete restoration of physiological airflow. Furthermore, we evaluate state-of-the-art optimization strategies across materials, structural design, and manufacturing modalities, encompassing silicone, nitinol, and biodegradable systems, advances in unit-cell and global configuration designs, and emerging three-dimensional (3D) and four-dimensional (4D) printing techniques tailored for patient-specific and bio-adaptive interventions. Ultimately, we highlight a pivotal transition in the field: moving away from isolating single-property improvements toward an integrated design paradigm that harmonizes mechanical support, flexibility, durability, and aerodynamic restoration with the dynamic, physiological demands of the host airway.