Mechanical failure in total hip arthroplasty with cement

Abstract

The long-term endurance of total hip arthroplasty (THA) depends on lasting mechanical integrity of the bond between implant and bone, the implant bone interface. If that bond, whatever its nature, is destroyed, the dynamic hip joint load produces relative motion between implant and bone. This results in inflammatory reactions, progressive interface bone resorption, fibrous-tissue interposition and, eventually, clinical loosening--this is the unchallenged adagium of successful THA. The question how to protect the interface from disintegrating is less easily answered. That is to say, there are answers in abundance, but there is no consensus. For most orthopaedic surgeons the matter is unresolved, not to say confused by manufacturers and inventors. 1'2 There is general consensus in the literature that two basic scenarios are likely to produce clinical failure to cemented interfaces) According to the particulate reaction scenario, wear particles (cement, polyethylene and metal) migrate in the interfaces, produce inflammatory reactions, and interface osteolysis and fibrous tissue interposition, which progressively debonds the cement from the bone. According to the accumulated damage scenario, the dynamic hip joint loads produce micro cracks in cement, implant cement and cement bone interfaces, relative motions, interface resorption and gradual debonding. These scenarios probably interact. Interface debonding by particulate reactions reduces the interface area available for load transfer, thus enhancing the probability of mechanical