[The causes of failure for hip and knee arthroplasties].

Most joint replacement prostheses in the hip or knee survive for longer than 10 years. Failure of a prosthesis may be due to infection or a fracture of bone or prosthesis, but much more often it has no clear cause, after a process of aseptic loosening. Mechanisms of aseptic loosening are: bone resorption as a reaction of bone to migrated foreign body particles, material fatigue due to repeated mechanical stress on the prosthesis and its connections with the bone, failed ingrowth due to a poor fit of the (uncemented) prosthesis in the bone bed, resorption of bone mass due to the prosthesis taking over part of the mechanical bone stresses, and wear of the material. The risk of early failure depends on the patient's bone quality and life expectation, on the surgical technique, the weight bearing on the prosthesis and the fixation, and the shape and materials of the prostheses. Selection of durable prosthetic types and techniques is being done more and more by means of stepwise introduction, (pre)clinical tests and post-marketing surveillance.