Remodeling of the tibial plateau after knee replacement. CT bone densitometry

We measured the changes of bone density by computed tomography of the proximal tibia after total knee replacement in 18 patients, 9 with arthrosis and 9 with rheumatoid arthritis. All the patients had good results after 1 and 2 years. There were no significant radiolucencies at the cement-bone interface. At the early postoperative measurements, we found abnormal mediolateral distributions of density, closely related to the preoperative tibiofemoral angle (r = -0.67). This distribution was within normal limits after 3 months in knees with preoperative valgus and after 2 years in knees with preoperative varus. The mean tibial density did not differ between patients with arthrosis and rheumatoid arthritis at the early postoperative examination, but the density in rheumatoid patients decreased by one third during the 2-year period. Although the overall change after knee replacement was loss of density, the preoperatively less loaded condyles had a slight tendency towards increasing density with time, a response that was considerable in some cases.