Trinity Centre for Bioengineering, School of Engineering, Trinity College, Dublin, Ireland.
Med Biol Eng Comput. 2011 Nov;49(11):1279-88. doi: 10.1007/s11517-011-0815-2. Epub 2011 Aug 11.
The use of stents in peripheral arteries has not been as successful as in coronary arteries, with high rates of restenosis and stent fracture common. Normal joint flexion induces a range of forces on the arteries, which has an unknown effect on the outcomes of stenting. The objective of this study is to determine how physiological levels of vessel bending and compression following stent implantation will influence the magnitude of stent stresses and hence the risks of fatigue fracture. A further objective is to compare how this mechanical environment will influence arterial stresses following implantation of either stainless steel or nitinol stents. To this end, models of both nitinol and stainless steel stents deployed in peripheral arteries were created, with appropriate loading conditions applied. At high levels of bending and compression, the strain amplitude threshold value for fatigue failure is exceeded for nitinol stents. Bending was predicted to induce high stresses in the artery following stenting, with higher arterial stresses predicted following implantation of a stainless steel stent compared to a nitinol stent. Both bending and compression may contribute to stent fracture by increasing the strain amplitude within the stent, with the dominant factor dependant on location within the arterial tree. For the specific stent types investigated in this study, the model predictions suggest that compression is the dominant mechanical factor in terms of stent fatigue in the femoral arteries, whereas bending is the most significant factor in the popliteal artery. To increase fatigue life and reduce arterial injury, location specific stent designs are required for peripheral arteries.
外周动脉支架的使用效果不如冠状动脉支架，再狭窄和支架断裂的发生率较高。正常关节弯曲会对动脉产生一系列的力，但其对支架置入效果的影响尚不清楚。本研究的目的是确定支架置入后血管弯曲和压缩的生理水平如何影响支架的应力大小，从而影响疲劳断裂的风险。进一步的目的是比较不锈钢和镍钛诺支架置入后，这种机械环境如何影响动脉的应力。为此，创建了外周动脉中部署的镍钛诺和不锈钢支架模型，并施加了适当的加载条件。在高弯曲和压缩水平下，镍钛诺支架的疲劳失效应变幅阈值被超过。支架置入后弯曲被预测会导致动脉内产生高应力，与镍钛诺支架相比，不锈钢支架置入后预测的动脉内应力更高。弯曲和压缩都可能通过增加支架内的应变幅导致支架断裂，主导因素取决于动脉树内的位置。对于本研究中调查的特定支架类型，模型预测表明，就股动脉中的支架疲劳而言，压缩是最重要的机械因素，而在腘动脉中，弯曲是最重要的因素。为了提高疲劳寿命和减少动脉损伤，需要针对外周动脉进行特定部位的支架设计。
