[Prognosis of total hip replacement: the importance of an implant register]

The survival of total hip arthroplasty is mainly determined by the loosening of implants. Wear particles generated at the articular contact of head and cup are engulfed by macrophages. These activated macrophages induce the production of RANKL, leading to proliferation and activation of osteoclasts resulting in osteolysis around the hip implant. Higher activity leads to increased particles production, which explains the lower survival rate of total hip arthroplasties in young patients compared to older patients. Implant fixation with bone cement still is an excellent technique, but uncemented techniques also give good results. Randomised controlled studies are necessary to give the final answer but are expensive. National hip registers are a good alternative and are an essential element for quality control.