Numerical research on the biomechanical behaviour of braided stents with different end shapes and stent-oesophagus interaction.

Quasi-static and dynamic numerical analyses are carried out by referring to computational models of commercial self-expandable braided stents with 3 commonly used end shapes, to evaluate the influence of different end shapes of stent on the biomechanical interaction between stent and oesophagus. The end shape has no influence on the equivalent stress, but has a great influence on the contact stress in the narrowest zone of the oesophagus-neoplasm system. However, the end shapes have significant effect on the equivalent stress and the contact stress in the healthy area of the oesophagus in contact with the stent ends. The results show that the maximum equivalent stress of the oesophagus occurs in the zone contact with the cup-shaped end and the maximum contact stress occurs in the zone contact with the edge of the trumpet-shaped stent end. Moreover, the stent apposition is almost not affected by the end shapes. Although small zones with an incomplete stent apposition appear in the transition zones of spherical-cup-shaped stent, such occurrence might not contribute to stent malapposition or stent migration. Therefore, these stents with 3 types of end shapes all have good stent apposition. Finally, the numerical simulation results can be used to assess the mechanical performance of stents with different end shapes, the effectiveness of stent expansion therapy, and the possibility of complications after stent implantation.