Designing a component for use in the human body is extremely challenging, and there are many regulations involved. In this blog post, we’ll talk about the top three polymers that are commonly used in medical implants:
- UHMW PE
PEEK (polyether ether ketone) is one of the most common choices when it comes to polymers for implantable mecial devices.
- excellent biocompatibility
- very good toughness
- resistance to heat
- excellent chemical compatibility
This combination of properties makes it perfect for critical load-bearing applications within the human body. For example, many designers are using PEEK as a component in the hip stem because it closely matches the natural flexibility of the human bone — better than previous materials used, such as titanium.
PEEK is easily sterilized through a variety of means, including steam, plasma and gamma irradiation, dry heat, vaporized hydrogen peroxide, and ethylene oxide. It can be used with a variety of manufacturing methods, including injection molding, extrusion, machining, laser etching, and overmolding.
Finally, PEEK is available in medical grade implantable forms are FDA and USP Class VI approved. However, a few of these PEEK grades are limited to 30-day body contact, but not all. PEEK can be an expensive option, but the combination of properties it provides along with its reliability make it well worth the investment.
2. UHMW PE
The next polymer that is commonly found in implantable medical devices is UHMW PE (ultra-high molecular weight polyethylene). UHMW PE is often used for articulating surfaces and found in shoulder, elbow, knee, and hip implants. Because of its excellent biocompatibility, it is also found in spinal implants.
UHMW PE offers excellent biological response to soft tissue and bone along with outstanding wear properties. It provides also provides strength, impact resistance, and stiffness. UMHW PE is non-sticking and self-lubricating. In addition, it can infused with anti-oxidants including Vitamin E.
The primary manufacturing techniques used with UHMW PE include injection molding, machining, and compression molding. Note that UHMW PE is available in various FDA approved grades.
Polysulfone (PSU) offers goods toughness and strength along with excellent dimensional stability. It is commonly used in neurovascular, cardiovascular, and drug delivery applications. It performs well even under the most rigorous sterilization methods, including steam, radiation, and ethylene oxide, and vaporized hydrogen peroxide.
It lends itself to injection molding, extrusion, pad printing, machining, laser etching, and overmolding. Grades are available that are both FDA and USP Class VI approved.
There are a few other polymers that are finding limited application in implantable devices. Polyphenylsulfone (PPSU) can be used for implantable devices, however its primary application is implantable wire coatings. It offers properties such as impact resistance, excellent toughness, and good insulation. PTFE is sometimes used, primarily because it is clean and remains inert in the presence of tissue and blood; its drawback, however, involves the limited load-bearing capabilities of the grades approved for implant.
Polymers are a valid alternative to the use of metal in implantable devices. PEEK, UHME PW, and PSU have been proven over the years and offer excellent properties that make them suitable for use in the human body. All three are available in approved grades, and have an excellent track record for performance, reliability, and compatability.
You may be interested in these additional blogs about seals for the medical industry:
- Custom Spring Energized Seals for Medical Devices
- 3 Challenges of Spring Energized PTFE & UHMW Seals in the Medical and Pharmaceutical Industry