(3% @ 10 years for cemented HRA femoral component)

Sometimes implants are initially well fixed to bone, but this bond can break down over time. His process is called loosening. Loose implants rub on bone and hurt. Uncemented implants are initially fixed to bone by a tight press-fit. But they are not truly considered fixed until bone ingrowth occurs. It can be difficult to know for certain if this process has occurred until you see a patient 2 years after surgery and they are without pain and have a stable x-ray. After that, if an implant becomes unstable w.r.t the bone it is thought to have loosened. This is extremely rare. It could possibly be caused by inflammation from excess wear debris (either plastic of metal).

In the Corin Cormet 2000 HRA we have seen 5/373 (1.3%) cases where the porous coating debonded from the uncemented acetabular implant causing loosening after 7 years of implantation. We have not yet seen this in the Biomet Magnum acetabular component, which we started using 7 years ago.

With cemented femoral components of HRA we have seen a 3% rate of loosening @ 10 years. We believe that this will not occur with the uncemented components. We started implanting these in 2007. It is still too early for us to see any difference statistically in the overall patient groups. However, in a small high-risk group of patients with osteonecrosis of the femoral head we have seen better results already.