Posted in Medical Materials – Form Supplied by MDDI Staff on January 18, 2017 /Len Czuba
I don’t think that there is any challenge more confusing to product development teams than selecting materials that can be used for long-term implantable medical devices.
Are there databases where implantable materials are featured? Can we go to our local supplier and ask them to recommend a material that can be used for implant applications? Usually the answer to both questions is “No.” There are not databases that offer a variety of implantable materials like produce at a supermarket, nor would they be accurate if they did exist.
As with most materials used in medical devices, the end use application dictates the selection of the material. The method of processing the component is critical, whether it is a molded part or an extruded tubing or a polymer used to coat a wire frame or filament. Each process has some effect on the material and factors into the choice of that material. The end product and how it is intended to be used helps define the requirements of the product and ultimately the materials selected for their construction. There are numerous possible products and each comes with significantly different material property requirements.
Consider these:
- Artificial heart valve
- Vascular graft
- Hernia repair mesh
- Pacemaker components, including (if used) the coating on wire leads
- Bone screws, pins, and plates
- Artificial joints: hips, knees, and shoulders
- Sutures, tissue anchors, and resorbable adhesives
Different Products, Different Requirements
Implantable products that are within the bloodstream and vasculature will need to withstand constant contact with all the components of circulating blood, including the aqueous environment, blood lipids, enzymes, and a barrage of blood components that often tend to recognize the implanted product as a foreign body.
Devices implanted in tissue, although often exposed to and surrounded by blood vessels, don’t have the same challenges as materials in the bloodstream. But since they are still foreign bodies in the tissue, they must not be adversely affected by the normal body’s response. For medical devices that are used with bone and joint surfaces, the materials used must also withstand the mechanical forces exerted on the implant, such as the moving surfaces of a joint replacement. If the implant surfaces result in any wear debris, the body will react and try to remove and or eliminate those particles.
