Gotman I
Department of Materials Engineering, Technion, Haifa, Israel.
J Endourol. 1997 Dec;11(6):383-9. doi: 10.1089/end.1997.11.383.
The performance of any material in the human body is controlled by two sets of characteristics: biofunctionality and biocompatibility. With the wide range of materials available in the mid-1990s, it is relatively easy to satisfy the requirements for mechanical and physical functionality of implantable devices. Therefore, the selection of materials for medical applications is usually based on considerations of biocompatibility. When metals and alloys are considered, the susceptibility of the material to corrosion and the effect the corrosion has on the tissue are the central aspects of biocompatibility. Corrosion resistance of the currently used 316L stainless steel, cobalt-chromium, and titanium-based implant alloys relies on their passivation by a thin surface layer of oxide. Stainless steel is the least corrosion resistant, and it is used for temporary implants only. The titanium and Co-Cr alloys do not corrode in the body; however, metal ions slowly diffuse through the oxide layer and accumulate in the tissue. When a metal implant is placed in the human body, it becomes surrounded by a layer of fibrous tissue of a thickness that is proportional to the amount and toxicity of the dissolution products and to the amount of motion between the implant and the adjacent tissues. Pure titanium may elicit a minimal fibrous encapsulation under some conditions, whereas the proliferation of a fibrous layer as much as 2 mm thick is encountered with the use of stainless steel implants. Superior fracture and fatigue resistance have made metals the materials of choice for traditional load-bearing applications. In this review, the functionality of currently used metals and alloys is discussed with respect to stenting applications. In addition, the "shape memory" and "pseudo-elasticity" properties of Nitinol-an alloy that is being considered for the manufacturing of urologic stents-are described.
生物功能性和生物相容性。在20世纪90年代中期有各种各样的材料可供使用，满足可植入装置的机械和物理功能要求相对容易。因此，医疗应用材料的选择通常基于生物相容性的考虑。当考虑金属和合金时，材料的腐蚀敏感性以及腐蚀对组织的影响是生物相容性的核心方面。目前使用的316L不锈钢、钴铬合金和钛基金属植入合金的耐腐蚀性依赖于它们被一层薄氧化表面层钝化。不锈钢的耐腐蚀性最差，仅用于临时植入物。钛合金和钴铬合金在体内不会腐蚀；然而，金属离子会缓慢地扩散穿过氧化层并在组织中积累。当将金属植入物置于人体中时，它会被一层纤维组织包围，该纤维组织的厚度与溶解产物的数量和毒性以及植入物与相邻组织之间的运动量成正比。在某些情况下，纯钛可能引发最小程度的纤维包裹，而使用不锈钢植入物时会遇到厚度达2毫米的纤维层增殖。卓越的抗断裂和抗疲劳性能使金属成为传统承重应用的首选材料。在本综述中，讨论了目前使用的金属和合金在支架应用方面的功能。此外，还描述了正在考虑用于制造泌尿系统支架的镍钛诺合金的“形状记忆”和“伪弹性”特性。
