This invention relates to an acetabular prosthesis.
It is well known that a major factor influencing the life expectancy of a prosthetic implant is fatigue fracture and wear. Frictionally induced torque stresses acting through the prosthesis can result in the breakage of either the bone or the cement used to bond the prosthesis to the bone. For example, the pressure placed on an acetabular implant during the course of normal movement can be as high as several tonnes/cm2. Such loads may lead to a very high risk of failure of the implant. If a breakage of the hip bone or cement occurs, wear is inevitable. This can lead to particle formation which causes osteolysis and adverse tissue reactions. These factors not only reduce the life expectancy of a prosthesis but can cause considerable damage to the bone of the patient.
Currently the life expectancy of an acetabular prosthesis is typically about ten years. If the prosthesis is to be implanted into an elderly patient then such a working life span is not problematic as the prosthesis might reasonably be expected to function for the lifetime of the patient. However, when such a prosthesis is implanted into a young patient, it is likely that one or more revision operations will have to be performed during the lifetime of the patient. It is highly undesirable to subject patients repeatedly to the trauma of such a major surgical procedure as is required to replace a failed prosthesis.