Osteointegration and implant position after cementless total knee replacement.

Osteointegration and implant position are regions of interest after cementless total knee replacement. The radiographic and functional status of 101 implants in 101 patients were evaluated 3, 12, and 24 months after implantation. To obtain satisfactory radiographs, a fluoroscopically assisted technique was used. In 92% of tibia interfaces, at least one wedge-shaped radiolucent area was visible without measurable changes of component position. The width of the gap increased from the central tibial area to the periphery. The shape was determined 3 months postoperatively. The femur could not be assessed for radiolucency because of the central metal crest design. In the current study, regularly appearing wedge-shaped radiolucent areas at the tibia interface, with the maximal width at the periphery, did not indicate aseptic loosening but showed that the forces of displacement had overcome initial mechanical stability, inducing micromotion of the implant. Osteointegration was seen only in central regions of the implant with minimal micromotion. Within the first year, partial bone ingrowth, fibrous fixation, and the surrounding bone gave satisfactory stability to provide secure fixation of the implant.