Clinical Advantages of PEEK Implants

Metallic implants like stainless steel have been in use in orthopedic surgeries for quite a while now. Titanium implants are slowly replacing the traditional metallic implants because of their better overall impact on patient care. A gradual transition to the use of Polyetheretherketone (PEEK) seems to be the next step in taking this process forward. (1) PEEK is being adopted as an innovative replacement to traditional metallic implant materials in orthopedics in recent times. PEEK offers some beneficial features over metals like steel and titanium. 

Radiolucency of PEEK implant allows full fracture visibility with imaging techniques like CT and MRI. Post-operative therapeutic monitoring for ailments like breakages can be done readily in cases when PEEK implants have been used. Metals are radio-opaque and MRI incompatible and hence do not allow medical evaluation of bone healing and soft tissue structures like the spinal cord thus posing a challenge to the periodic monitoring of defects. PEEK being radiolucent is visible in scans and allows such procedures safely. Improved visibility with PEEK implants allow monitoring and increased confidence in the overall process of healing. The patient can be returned back to stress bearing activities at an appropriate time with the better visibility offered by PEEK implants.

PEEK is comparable to metals in terms of strength and stiffness. It resembles natural bone more closely than metallic implants. (2) This property reduces stress on the bone and prevents stress shielding, an adverse effect commonly seen with metallic implants leading to reduction of bone density. The polymer can be easily modified into complex geometrical shapes as desired. (2) Owing to its favorable modulus of elasticity (Young’s modulus), PEEK allows enhanced stress absorption and better weight-bearing. This contributes to the process of healing and makes it faster. PEEK also offers ergonomic benefits as it offers the strength of metal while being lightweight. Metallic implants are known to cause some discomfort themselves which is not an issue with the use of PEEK implants. This has a significant positive impact on the quality of life of the patient. 

It is essential for an implant not to cause adverse effects itself to the patient. Cases of chronic heavy metal poisoning have been reported from metallic implants (mostly metallic implants like cobalt, nickel, titanium, and molybdenum). This extremely undesirable effect is not seen with polymer implants like PEEK.   The biocompatibility of PEEK is also an important factor responsible for its increasing popularity in orthopedics. Numerous studies were done on the systemic and cutaneous toxicity and muscular implants have shown no adverse effects of PEEK bio implants. Gene toxicity tests have also shown no chromosomal aberrations attributable to PEEK implants. Better biocompatibility means better healing and lesser risks of implant failure.  PEEK is also resistant to damage caused by body fluids and lipids. This also contributes to the increased long term efficacy of the polymer implant.  

Studies have shown huge economic burdens due to delayed or non-union of bones leading to revision surgeries and implant removal. Non-union rates as high as 19% for distal femoral plating are reported from several studies. These problems are more pronounced nowadays due to the increasing prevalence of comorbidities like diabetes, obesity, and osteoporosis.  The associated negative effects on the quality of life of the patient also cannot be overlooked. PEEK implants has lower rates of implant failure because of its high material fatigue life. Implant removal surgeries with PEEK are less complicated compared to metallic implants. The ease of implant removal reduces the operating time and costs of surgeries significantly. 

A case worth mentioning is that of UK Olympic team sprinter James Ellington. He competed in the 2016 Rio Olympics was badly injured in a motorcycle accident in January 2017. He survived multiple injuries including a fracture of the right tibia and fibula, a fracture of the left ankle, a fracture of the eye socket, and a broken pelvis. His physicians from the University College London Hospitals opted to use PEEK bio-implants for the fracture repair in the right leg. It included the insertion of a composite nail made with PEEK-Optima Ultra Reinforced. (3) His injuries which were regarded almost fatal and certainly career-ending were resolved in around 2 and a half years. He was back to fitness and was all set to compete in Tokyo Olympics 2020. (4)

PEEK has become injection moldable and extrudable in the past decade which means it is possible to adjust the properties of this bio implant further with additives like carbon fiber, barium sulfate, and glass fibers to achieve the desired biomechanical parameters. 

Thus PEEK can be an answer to a multitude of implant requirements in orthopedics and trauma surgery. (5) In addition of the low manufacturing cost of PEEK implant than that of metallic implants, advantages like radiolucency, lightweight, durability, and reusability adds in support heavily in the long run. In years to come further modifications in PEEK bio-implants will expand its scope in orthopedics. PEEK bio-implants thus seem to be the future of orthopedics and trauma surgery in near future.