|January 17, 2017
J. Med. Devices
, (2017); doi: 10.1115/1.4035723
The interest in biodegradable polymers for clinical and biomedical engineering applications has seen a dramatic increase in the last ten years. Recent innovations include bioresorbable polymeric stents (BPS); temporary vascular scaffolds designed to restore patency and provide short-term support to a blocked blood vessel. BPS offer possibilities to overcome the long-term complications often observed with permanent stents, well established in the treatment of vascular disease. From the perspective of designing next generation BPS, the bulk degradation behaviour of the polymer material adds considerable complications. Computational modelling offers an efficient framework to predict the behaviour of medical devices and implants. Current computational modelling techniques for the degradation of BPS are either phenomenologically or physically-based. In this work, a physically-based polymer degradation model is implemented into a number of computational frameworks to investigate the degradation of a number of polymeric structures. A thermal analogy is presented to implement the degradation model into the commercially available finite element code, Abaqus/Standard. This approach is then applied to the degradation of BPS, and the effects of material, boundary condition and design on the degradation rates of the stents are examined. The results indicate that there is a notable difference in the molecular weight trends predicted for the different materials and boundary condition assumptions investigated, with autocatalysis emerging as a dominant mechanism controlling the degradation behaviour. Insights into the scaffolding ability of the various BPS examined are then obtained using a suggested general relationship between Young's modulus and molecular weight.