Replacing metal for medical implants

An ageing global population is pushing the demand for implantable medical devices. For healthcare professionals in search of a solution to effectively replace metal in joints and spines, Zeniva® polyetheretherketone (PEEK) is worth exploring. Here’s why.

Implantable medical devices for orthopedic, cardiovascular and dental uses are increasingly common. That’s because access to high quality healthcare has been improving, particularly in Asia, and the population’s needs are increasing as we age, especially in Europe and North America. Among the solutions Solvay offers in the field of healthcare and wellness, Zeniva® PEEK as a long-term implantable material has much to offer.

The traditional go-to solution to make implants is metal, but as in many other fields (such as for medical instruments and accessories, as well as for planes and cars…), replacing it with high performance plastics has advantages: strength, durability and flexibility in addition to biocompatibility, to name a few. Because of this, implantable devices made of Zeniva® PEEK are capturing the attention of implantable device manufacturers and orthopedic surgeons.

What makes implantable polymers so effective?
First of all, Zeniva® PEEK is a biocompatible material with properties similar to those of human bones, with comparable stiffness (‘modulus’ is the technical term) for example, as opposed to unnaturally hard metal. This helps it integrate within the body harmoniously.

What’s more, its radiolucent properties (meaning its transparency to X-rays) help the reading of x-rays and CT scans. “Compared to metal, it doesn’t light up brightly on the image, which means you can distinguish details much better,” says Jeff Hrivnak, Business Development Manager for Healthcare at Solvay’s Specialty Polymers. “And surgeons appreciate that.”

Finally, Zeniva® PEEK diminishes the risk of adverse effects that can be caused by metal implants such as allergies (specifically to heavy metals) and ion erosion (potentially harmful metal particles released from the implants).

The number one application for Zeniva® PEEK is spinal cages (see image above), or ‘interbody fusion cages’. These are cylindrical prosthetic devices that help to restore the spine’s correct alignment, which is one of the main reasons for spine surgery.

Screws to fix joints following a trauma is another important use, and knee replacements (see image below) are a major future target: “There are hundreds of thousands of knee operations a year,” says Jeff.

PEEK from cars to knees
Solvay entered this market about a decade ago. PEEK was already used in a variety of other fields, from automotive and aircraft components to 3D printing. It also had certain applications in healthcare, but extending its use to implantable medical devices was a lengthy process. “Going into the implant market is not something you can take lightly,” says Jeff. “We had to work hard to conduct biocompatibility testing and make sure the material met regulations so we could supply all that information to manufacturers in order to speed up the certification process.”

But in the end, the facts speak for themselves: PEEK is considered one of the most respected materials on the market for structural applications such as orthopedics, where performance in terms of strength and durability is just as crucial as biocompatibility. As such, it represents yet another example of the benefits of polymers in a wide range of healthcare applications, from membranes for hemodialysis to blister packs to protect pharmaceutical drugs.

Ongoing efforts to make Zeniva® PEEK even better suited for medical implants include improving its integration into the very structure of the bone. “We’re helping to improve the way bones grow into the implant by collaborating with many different small companies that are working on technologies that boost bone integration,” explains Jeff. “It’s crucial to remain on the forefront of innovation in order to better serve humanity.”