Mechanically governed fracture resistance of biodegradable Zn-Cu alloy stents: Role of ring-length optimized structural design

Zinc alloys containing copper, featuring highly soluble biocompatible elements, are widely regarded as one of the most promising candidates for use in biodegradable stents. However, suboptimal structural designs in biodegradable zinc alloy stents often lead to immediate strut fracture upon deployment. Although ring length plays a critical role in this failure mechanism, systematic studies focusing on enhancing fracture resistance through structural design-rather than material modification-remain limited. This study engineered three distinct ring length configurations (approximating radial strengths of 89 kPa, 120 kPa, and 150 kPa) to elucidate structural optimization effects on fracture resistance during biodegradable zinc alloy stents expansion. Our results demonstrate that stents with 89 kPa and 120 kPa radial strength exhibit superior fracture resistance, whereas the 150 kPa design shows significantly elevated fracture incidence. Mechanistic analyses reveal that the capacity for geometric plasticity accommodation constitutes the dominant fracture-resistant mechanism, beyond intrinsic material properties. This capacity is achieved through stress redistribution, which mitigates localized peak stress. Optimized stents achieved uniform expansion, perfect vessel apposition, and preserved structural continuity. Histological analysis revealed a confluent endothelial layer covering the stent struts at 1 month. These findings reveal a direct relationship between structural plasticity accommodation capacity and mechanical integrity preservation, providing critical insights for developing next-generation bioresorbable stents with enhanced structural reliability. • Ring length serves as a critical design parameter governing fracture resistance in biodegradable stents. • Shorter ring unit length (1.30 vs 1.45 mm) increases radial strength 69% but exacerbates stress concentration at crown apices. • Stress redistribution to low-strain zones prevents fracture despite identical Zn-1.0Cu composition. • Optimized stent (120 kPa) achieves complete endothelialization and perfect apposition within 1 month in vivo.