Special materials are needed to produce and apply suitable, customized implants. But not only stability and elasticity is important. Also, corrosion resistance and biocompatibility are criteria, that need to be kept in mind when producing implants. COMPAMED-tradefair.com talked with Hermann Schmidt about material development for implants.
What material do you use?
Hermann Schmidt: Euroflex specializes in processing and distributing metallic materials for the medical technology sector. These are obtainable as tubes, wires or belts as well as components of these items.
What materials do you produce?
Schmidt: Generally, we process semi-finished materials into semi-finished products. Our core business is the processing of Nitinol – nickel-titanium alloys. Over the years, we have added other materials such as cobalt-base alloys, titanium alloys and surgical stainless steel for medical applications into our portfolio – as well as special materials such as tantalum, platinum, magnesium and zinc alloys.
How is the manufacturing process broken down?
Schmidt: The production of semi-finished products includes countless metal forming steps with annealing and cleaning processes. For example, a tube that is later processed into a stent can easily run through more than 400 process steps.
What are the special characteristics of the individual materials?
Schmidt: Each material has unique properties. Because of its exceptional superelasticity, Nitinol, for instance, is often used in body regions with frequent high-intensity movements. What's more, the material also has shape memory property, allowing you to train it to assume a specific shape. In turn, stainless steel and cobalt-based materials offer high rigidity and stiffness and are most commonly used in coronary applications. In terms of corrosion resistance and subsequent biocompatibility – a crucial factor for implant success – NiTi, cobalt-base alloys L605 and MP35N as well as surgical stainless steels like 316LVM, set themselves apart from standard materials.
Which materials are best suited for which implant or applications, respectively?
Schmidt: That entirely depends on the requirements that must be derived from the knowledge of the physiological conditions. In the case of coronary blood vessels, the stent needs to open the stenosis by dilating the balloon. As a result of the cold deformation produced by the dilation, a high radial force needs to be exerted to keep the vessel from collapsing. The best materials for this are stainless steel and cobalt-base alloys. When it comes to stainless steel, there is also an available nickel-free version that opens up future treatment options for allergy sufferers. For several years now, the use of resorbable materials in the coronary vessel sector has also been viewed as an opportunity to improve treatment methods. Magnesium and zinc alloys are especially well suited for this. A fast-growing field is the use of reinforced metal frames for heart valves. Nitinol is a material that makes it possible to insert the heart valves in a retracted, folded-up state through the femoral artery. In contrast, a balloon expandable version uses a cobalt-base alloy for example.
How can materials and processes still be improved?
Schmidt: The metallic materials used in medical technology so far are often "adopted" materials used in other industry sectors that must be optimized for future use in and on the human body. Oftentimes, the technical grade of purity is not ideal for the application, for instance when used in tiny structures, as is the case with neurosurgical implants. There have already been efforts to improve these conditions. The Euroflex Company specifically collaborates with research facilities to contribute to medical progress.
What do manufacturers of implants and physicians emphasize when it comes to materials?
Schmidt: Manufacturers value ever closer tolerances and premium quality. Purity is also an important topic, even if we as a manufacturer of semi-finished products currently only come into contact with this in a limited manner. After all, our products still undergo numerous other process steps at our customers. Physicians primarily want better treatment methods for their patients. As a tool specialist and manufacturer of components, this prompts us to continually advance our processes and widen our range of materials.
What innovations are you currently striving for?
Schmidt: New minimally invasive treatment methods always require new material concepts. For example, it should be possible to insert complex structures such as aortic or mitral valves through the femoral artery or the apex of the heart in a folded-up shape, while simultaneously exhibiting a high fatigue resistance in a fully expanded state. To meet these and similar requirements, we have developed an ultrafine Nitinol – Nitinol HCF-SE (high-cycle fatigue) –, which compared to standard versions, exhibits improved fatigue behavior by a factor of one to two. Combined with materials like tantalum or platinum alloys, it allows for the production of optimized materials that lead to new products and ultimately also benefit the patient.
As a subsidiary company of G.RAU with its headquarters in Pforzheim and great successes with its technologies in metal forming since 1877, we have the necessary know-how to act as a development partner for our customers. We regularly offer this service to our customers, which sets us apart from our competition. Our recent independent enhancement NiTi HCF SE should be emphasized here. This is an ultrapure Nitinol material that offers special benefits in terms of product lifespan.