Biodegradation of the copolymeric polylactide stent - Long-term follow-up in a rabbit aorta model

The behavior of biodegradable polylactide as a stent material has not yet b een fully established in small vessels such as arteries with a diameter <3 mm. The aim of this study was to investigate the long-term effect of a copo lymeric polylactide (PLA96) stent. Appropriately sized spiral PLA96 stents were implanted into the infrarenal aortas of 20 rabbits. Intraoperative sys temic heparinization (150 IU/kg), perioperative subcutaneous enoxaheparin s odium (10 mg), ticlopidine (250 mg/day) for 1 month, and acetosalicylc acid (12.5 mg/day) were continuously administered. Animals were euthanized acco rding to a fixed timetable for up to 34 months for histologic and scanning- electron-microscopic assessment. Endothelialization was complete within 1 m onth. In 2 of the 3 aortas sampled 3 months after implantation, a mild infl ammatory reaction was visible, with no sign of granulomatous or foreign-bod y reaction in the vessel wall. Instead, in 1 sample examined at the same ti me point, neointimal chondroid metaplasia was detected. After 6 months, inf lammatory reaction declined in the vessel wall. Hydrolyzation of the stent was histologically evident at 12 months, with mild foreign-body reaction de tectable in 2 of 5 aortas sampled at this time point. The stent disisegrate d without fragmentation by 24 months, as it was gradually replaced by fibro sis. The vessel lumen remained patent at all time points. We conclude that the PLA96 stent degraded with minimal tissue response within 24 months. PLA 96 may thus be a promising stent core material for small vessels in the fut ure, although further investigation is needed to establish its final biocom patibility. Copyright (C) 2001 S. Karger AG, Basel.