SHAPE MEMORY ALLOY INSTRUMENTS AND DEVICES FOR MINIMAL-ACCESS THERAPEUTIC INTERVENTIONS

摘要

Aside from their unique properties, NiTi SMAs have a number of attributes that render them ideal for use in surgical instrumentation, the most important being biocompatibility, extremely low toxic-ity, and corrosion resistance. Thus, they can be used as implants such as ligatures and sutures without causing any long-term deleterious effects. Another practical advantage with respect to surgical instruments is that they withstand sterilization by autoclaving. Since NiTi SMAs are nonferromag-netic, they can be used as the material for instrumentation employed in magnetic resonance guided interventions using open-magnet systems. Unlike stainless steel, any SMA implants will not cause distracting artifacts that degrade subsequent MRI imaging. However, NiTi SMAs can be expensive and, thus, materially increase the costs of surgical instrumentation. In addition, they pose substantial machining difficulties that limit the use of SMAs as a general construction material. SMAs can be used predominantly in their superelastic mode, for robust structures, constant force springs, and large extension/deflection spring elements using standard round wire or rectangular strips. In some situations, however, exemplified through tissue approximation by SMA constructs, temperature-dependent shape memory recovery offers the best solution.