There are mainly two types of fixation to hold the prostheses in position: cemented fixation, in which
fast curing bone cement is used to hold the prostheses in place, and cementless fixation, which relies
on bone growing into the surface of the implant for fixation. Both of the two have their own advantages
Most knee replacement implants today are cemented, and normally they act very well. The stability of
cemented fixation relies on the connection between the prostheses and the cement, and the adhesion
between cement and bone is also very important.
Cementless implants have a surface topography that is conducive to attracting new bone growth. Most
are textured or coated so that the new bone actually grows into the surface of the implant. They may also
use screws or pegs to stabilize the implant until bone ingrowth occurs. Since they depend on new bone
growth for stability, cementless implants require a longer healing time than cemented replacements.
Both of the two type’s implants may suffer from loosening and wear. In daily movement, the implant is
under considerable amount of load, and the bone may not be able to support the implant, so there may
be relative motion between the implant and the bone, after a long time, the implant will become loose,
then the bone may be damaged and brings new pain. Although the surfaces of both the metal and plastic
part are already polished, there will still be significant friction to produce debris, and the debris will
damage the bone and leads to new disease.