John Insall, who performed the first knee arthroplasty in 1973, said that total knee arthroplasty is a bone surgery, but more importantly, is a soft tissue stabilizing surgery.
Simple designs that were used for the first total knee arthroplasty had evolved to be more different and elegant materials as the technology progressed.
Total knee arthroplasty consists of three separate components that are femoral component, tibial component and patellar component. Nowadays, there are cementless prosthesis designs, still, cemented prostheses are more widely used. That is the reason why the properties of cemented prostheses will be discussed.
Femoral component is made of cobalt chromium material; inner surface has a rough coat to be compatible with cementing, outer surface has a shiny, smooth lining. Occasionally, oxinium or ceramic femoral components are used for posttraumatic gonarthrosis of younger patients.
Tibial component is made of titanium material. Superior surface is shiny and smooth, while inferior surface is rough to be compatible with cementing. Additionally, inferior surface has wedge or protrusion to provide rotational stability.
Even though, polyethylene on top of a metal backing was used in earlier versions of patellar component, nowadays, completely polyethylene components are used to be compatible with cementing. On the inferior surface, it has a single central, large protrusion or three small peripherical protrusions to enhance stability.
One of the most important parts of total knee arthroplasty is the polyethylene insert. These inserts can be mobile or stable. Generally, stable inserts are preferred. To provide soft tissue stability, these inserts can be used as nonconstrained (PCL retaining), semiconstrained (PCL sacrificing) and constrained (hinged). In general, for the patients whose soft tissue stability cannot be maintained semiconstrained inserts are chosen; for the patients who had bone tissue loss in addition to soft tissue instability, hinged prostheses are used.
