Biocompatible polymers are medical-grade plastics that are safe to use in medical applications. Some of these polymers can be implanted for many years without fear of causing a toxic or allergic reaction. This degree of safety, paired with polymers’ versatility and durability, means biocompatible polymers are a promising area of medical research.
Biocompatible polymers include:
- Polystyrene (PS)
- Polypropylene (PP)
- Polyvinyl chloride (PVC)
- Polyethylene (PE)
- Polyurethane (PU)
- Polycarbonate (PC)
- Polyethylene terephthalate (PET)
- Polyetheretherketone (PEEK)
These polymers are featured in an array of medical devices, instruments and components, from single-use medical tubing to highly sophisticated spinal implants.
How are biocompatible polymers used in medicine?
Biocompatible polymers are rapidly replacing metals throughout medicine, especially where it concerns PEEK. PEEK is a high-performance biocompatible polymer, so it provides several important material properties that other polymers, including biocompatible polymers, can’t.
PEEK is found in a number of medical fields, including the following long-term implantable application areas:
- Cervical and lumbar spinal fusion – PEEK’s first long-term implantable medical success was in cervical and lumbar spinal fusion, where it is still the first choice for interbody fusion cages. PEEK has steadily replaced titanium as the front-line option in this area, due to its superior flexural modulus, radiolucency and processability. PEEK cervical and lumbar fusion cages have been in use for over 20 years, and two decades of patient reports confirm that the polymer is an effective and safe choice.
PEEK spinal rods are also gaining traction in lumbar decompression and fusion procedures. Lumbar decompression was once rare, as it was considered a high-risk treatment with more conservative alternatives. Improvements to the procedure and to the implants associated with the procedure have made it more commonplace. PEEK is incorporated into lumbar rods and implanted during lumbar fusion, which is typical following lumbar decompression.
- Orthopedic devices – PEEK is found in various orthopedic devices, including devices used during knee and hip replacement. PEEK’s wear resistance and fatigue strength are important traits to have in an orthopedic device, especially in weight-bearing surfaces. As such, PEEK is finding use in acetabular cups, where it can provide stable, reliable support for many years, without fear of shedding particles like metal implants do occasionally.
- Cardiovascular devices – PEEK’s processability means it can be converted using one of several methods, including extrusion and more exotic conversion methods like film calendaring. This processability advantage is critical for cardiovascular devices and instruments, many of which require medical tubing to function. PEEK is an ideal medical tubing biomaterial, as it possesses excellent column strength and tensile strength. It is an ideal fit for the constant push and pull found in the cardiovascular network.
PEEK also has an ideal flexural modulus, which means it is flexible enough to navigate through winding segments, but stiff enough that it will not buckle. It requires a modest amount of force to push into the patient, and PEEK offers a good torque response, which makes it a frontline choice for catheters.
PEEK is also found in stents and replacement valves, as well as defibrillators, where their ability to isolate electrical pulses prevents accidental shock. PEEK is also an essential biomaterial for some complex cardiovascular procedures, like the Less Invasive Ventricular Enhancement (LIVE) procedure. The LIVE procedure is usually administered to people with severe ischaemic heart failure and involves reshaping the left ventricle so that the heart handles blood more efficiently. The LIVE procedure relies on a pair of anchors to secure the ventricle in its new position, and these anchors are kept in place using a PEEK tether. PEEK’s tensile strength and resilience are major advantages in this context.
- Trauma fixation – PEEK is used in a variety of trauma fixation devices, including interference screws and bone plates. The biocompatible polymer’s fatigue strength and pullout strength are notable for trauma fixation applications, as is the material’s flexural modulus.
Ideally, a trauma fixation device, which is typically used to facilitate bone healing, would do so by encouraging the damaged bone to grow back. PEEK, with its bone-like modulus, does this exceptionally well. The polymer protects the bone from excessive tensile or compressive forces but subjects the bone to enough stress to promote growth.
PEEK’s pullout strength is important for trauma fixation hardware like screws, nails and anchors. PEEK flexes enough that it resists being pulled out of bone or a bone plate. The result is a more reliable device that promotes total healing.
- Dental – PEEK has a sizable role in dentistry and is an ideal option for partial dentures and dental implants. PEEK’s viability as a dental implant is due, again, to its bone-like modulus. As a partial denture, PEEK is prized for its aesthetic qualities, as it can be color matched to nearby tissues, making it nearly impossible to see the device. PEEK dentures also offer superior comfort, as they do not cause allergic reactions, are lightweight, do not trap heat and do not alter the patient’s sense of taste. In short, there’s a lot for patients to like with PEEK.
There are many biocompatible polymers in medicine, but PEEK is the most accomplished among them. With unparalleled versatility, safety and processability, PEEK is quickly becoming the world’s most advanced biomaterial.