DECREASED BONE-DENSITY OF THE DISTAL FEMUR AFTER UNCEMENTED KNEE ARTHROPLASTY - A 1-YEAR FOLLOW-UP OF 29 KNEES

We measured the early adaptive bone remodeling of the distal femur pro spectively for 1 year after uncemented total knee arthroplasty (TKA) i n 29 knees with primary arthrosis. 18 patients were randomized to rece ive a PCA Modular(R) femoral component (n 9) or a modified version of the same prosthesis (n 9) with an altered location of the porous coati ng. The other 11 patients(n Il)formed a consecutive series with the Du racon(R) femoral component. In the trabecular bone above the femoral c omponent, bone mineral density (BMD) was measured in 2 regions of inte rest (ROI) anteriorly to the fixation pegs (ROI 1) and above the pegs (ROI 2), using dual photon absorptiometry (DPA). There were no differe nces between the Modular component and the modified version regarding the postoperative decrease in BMD. There was a decrease in BMD in both ROI 1 and ROI 2 with all 3 different femoral components, and in both ROIs the highest bone loss rate was observed during the first 3 months after surgery. On average (n 29), a significant bone loss of 44% and 19% in ROI 1 and ROI 2, respectively, was reached at the I-year follow -up, compared to the initial values. A decrease of this magnitude in B MD in the anterior distal femur 1 year after TKA, may be an important determinant of periprosthetic fracture and later failure of the femora l component. In this experimental set-up, a modified femoral component with an altered location of the porous coating did not influence the development of bone loss.