Mechanical analysis of tracheal anastomosis reinforcement through cartilage regeneration: a finite element study on regeneration site configuration.

Postoperative bronchial fistula and anastomotic stenosis remain significant concerns in lung cancer surgery requiring bronchial reconstruction. Previous studies have shown that basic fibroblast growth factor (bFGF)-induced cartilage regeneration could stabilize anastomosis sites and replace conventional tissue coverage. To inform the optimal configuration of bFGF-based protocols, this study evaluated the relative mechanical effects of varying the number and arrangement of regeneration sites. We developed a mechanically equivalent two-dimensional finite element model based on rabbit tracheal anatomy, with material properties calibrated against quasi-static tensile measurements on whole-trachea component specimens. Stress distributions and principal stress directions were analyzed across configurations of 0, 2, 4, and 8 sites under two loading scenarios: 50% strain (postoperative environment) and 100% strain (surgical upper bound). Across both conditions, as few as two sites were sufficient to eliminate compressive stress at the anastomotic plane, redistribute hydrostatic and principal shear stresses to anchor the cartilage regions, and reduce the angular deviation of the maximum principal stress from the longitudinal axis by approximately 35-36%. Additional sites beyond two showed marginal benefit. The model further predicted that regenerated cartilage progressively suppresses tension-induced anastomotic contraction, with the loaded anastomotic diameter rising from approximately 79% of the cartilage diameter without regeneration to 91% with two sites and 95% with eight sites. While two sites provided sufficient mechanical support in this idealized analysis, the trachea-bronchial system's anatomical complexity suggests a four-point approach warrants further preclinical investigation. These findings provide a mechanical basis for validating cartilage regeneration protocols addressing both anastomotic stability and stenosis prevention.