Research on the Fretting Wear of Braided Units in Nonvascular Stents

This study aimed to analyze the fretting wear between the wires of braided nonvascular stents implanted in pathologically narrowed nonvascular lumens, using finite-element numerical simulation and experimental methods. A suitable and representative braided unit from a typical esophageal stent was selected to simulate fretting wear under two distinct pathological tissue growth patterns within the esophagus: uniform circumferential growth (CASE1) and unilateral growth (CASE2). The accuracy of the simulation was verified by comparing it with experimental data, and the profiles and morphological features of the wear scars were meticulously analyzed using scanning electron microscopy. The study found that the wear between the wires of the braided unit is primarily sliding friction, with mutual influence across the four contact regions, resulting in approximately elliptical wear scars. As the number of cycles increased, the wear depth and volume loss gradually increased, demonstrating the cumulative effect of wear over time. CASE2 exhibited higher normal contact forces across all contact areas compared to CASE1, resulting in greater wear depths and volume loss. After 1 million cycles, distinct wear marks were noted in the wire contact areas without any significant cracks. Discounting the influence of the acid-base wet environment, the risk of stent fatigue failure attributed to fretting wear within 3 years is assessed as low. Nevertheless, the wear debris generated on the worn surfaces poses a potential risk for inducing local inflammation, a factor that warrants further investigation. The study results are valuable for improving stent design, ultimately enhancing patient safety and treatment efficacy.