Polyethylene Knee Insert Reduces Oxidation Risk

A novel knee insert made of highly cross-linked polyethylene blended with vitamin E enhances wear resistance, without compromising oxidative stability and mechanical properties.

The E-XPE insert is indicated in knee arthroplasty for reduction or relief of pain and/or improved knee function in skeletally mature patients with severe knee pain and disability due to rheumatoid arthritis (RA), osteoarthritis (OA), primary and secondary traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle, pseudo-gout, and post-traumatic loss of joint configuration, among others. It may also be indicated in the salvage of previously failed surgical attempts, if the knee can be satisfactorily balanced and stabilized at the time of surgery.

The single use insert is made of highly cross-linked polyethylene blended with 0.1% vitamin E, which is intended to reduce the oxidation caused by free radical generated during the sterilization irradiation process and the thermal treatment of the polyethylene insert. The E-XPE insert is a product of United Orthopedic Corporation, is available in CR, PS, UC, PSA, and patella configurations, and has been approved by the U.S. Food and Drug Administration (FDA).

“Oxidation continues to be a concern for surgeons. The E-XPE polyethylene is resistant to oxidation and performs extremely well with respect to abrasive wear resistance,” said Calvin Lin, President of United Orthopedic Corporation. “Our E-XPE polyethylene knee insert represents an important milestone in our knee portfolio.”

The majority of knee replacements consist of metal femoral and tibial components with a polyethylene liner inserted between the two articulating surfaces. Although designed to withstand the substantial forces that are transmitted across the knee joint during everyday activities, the friction generated by the articulating surfaces results in wear of the plastic liner, releasing small particles of polyethylene that activate the body’s immune system, triggering an inflammatory response and causing the bone around the knee replacement to be reabsorbed. The result is that the knee replacement becomes loose and painful, known as aseptic loosening.