DELAYED-TYPE HYPERSENSITIVITY TO IMPLANT MATERIALS: ALTERNATIVES IN KNEE ARTHROPLASTY

Knee Implants are usually made of CoCr28Mo6 or TiAl6V4 alloys or combinations of both materials in modular junctions. Particles and metal ions from knee implants are always released after implantation, either as a result of mechanical (wear) or electrochemical processes (corrosion). Total knee arthroplasties (TKA) are very effective treatment options for advanced osteoarthritis of the joints with overall low revision rates [1–4]. However, biological reactions in patients (allergy, inflammatory response), caused by the release of metal particles and ions, have been reported [4–8]. An overview will be given about alternative implant materials and their biotribological properties, biological reactions and clinical results to substantially reduce metal ion release in knee arthroplasty. Methods. Implant materials are usually well tolerated, but if a critical metal ion concentration is exceeded, local or systemic reactions can occur. The released metal particles and metal ions accumulate around affected joints as well as in body fluids and distant organs. Local tissue reactions to metal particles around joint arthroplasties have been described by the term “adverse reactions to metal debris”. Based on the alloy composition of established implant materials their biotribological behaviour with release of metal debris and Co, Cr, Mo, Ni, Ti ions will be demonstrated in meaningful examples with a focus on adverse biological reactions, clinical findings in patients with suspected metal ion hypersensitivity and implant registry results. If patients present with a confirmed metal allergy, in TKA a ZrN-multilayer-coated or oxidized zirconium implant is currently the best option [5,6,8]. To address hyper-sensitivity reactions to bone cement constituents [9], up-coming innovative implant technologies based on ceramic-coated 3D-printed TiAl6V4-alloy with cementless bone fixation represent a future perspective.