B Masson
Toulouse – France
Total knee replacement (TKR) is a successful procedure in orthopaedic surgery and the incidence of knee replacement in young and active patients is increasing. Consequently, knee replacements must be able to offer longer implant lifetime. This is why the choice of implant material is so important, especially with respect to the biological behaviour and wear properties of the selected material. Current research is focusing on new materials and ceramic can play an important role in increasing the lifetime of the components.
The worldwide circulation of ceramics in total hip replacement is justified through its extreme wear and corrosion resistance because of the excellent tribological properties and the absence of electrochemical reactions. Using these advantages, as well as finding a solution in cases of hypersensitivity against metallic implant materials, led to the development of total knee replacement systems with ceramic components.
Knee replacement implants are usually made from either cobalt chromium alloy or titanium alloy articulating on polyethylene. Clinical evidence and long term results show that aseptic loosening limits implant lifetime. One of the most important causes of aseptic loosening is the wear of polyethylene.
In total knee arthroplasty, ceramics revealed superior experimental data concerning low wear rates as well as promising results of the first clinical applications.
Literature also suggests that immunological and allergic responses to metallic elements (cobalt, chromium and nickel) contained in the alloys used in metallic implants are also a possible cause of aseptic loosening and post-operative complications such as delayed wound healing and skin reactions.
By reducing the wear rate and the risk of allergic response, ceramic knee should increase the survival rate of the TKR.
However, ceramic materials are less resistant especially in bending strength in comparison to metallic implants. This requires components with sufficient thickness, which can lead to increased bone loss. Major prerequisite should be the optimization of existing designs of the femoral ceramic component. There is still a need for further development and adequate preclinical testing.
Because the life expectancy of the population as a whole is greater now than ever before and the desire for improved quality of life after knee replacement has increased, ceramic knee could be one of the answers.