Different Methods of Implant Fixation in Primary Knee Arthroplasty

Abstract

The three components that make up a total knee replacement can be secured to bone using either cemented or cementless fixation. Cemented fixation relies on the polymer polymethylmethacrylate (PMMA) to secure the implants. Cementless fixation relies on either a porous metal surface or a contoured surface coated with hydroxyapatite (HA) to promote bone ingrowth and subsequent stability. The articulation (and wear) occurs between the metal femoral component and the polyethylene of the tibial component. Tibial components can either be manufactured entirely from polyethylene, or from metal on to which a polyethylene insert is secured. Although cementless patellas have fallen out of favor due to high failure rates. There still remains some interest within the orthopedic world about the role of cementless fixation, particularly of the tibial component. This is because the most common noninfectious failure mechanism of TKA is loosening of the tibial component secondary to tibial bone osteolysis (resorption) caused by polyethylene debris arising from wear of the bearing surface. It is postulated that cementless fixation may ultimately result in improved TKA longevity by preventing polyethylene debris from gaining access to the bone–implant interface.