Periprosthetic bone mineral density of the distal femur after total knee arthroplasty.

Evaluation of the bone mineral density (BMD) was performed in the distal femur around the femoral component of a total knee prosthesis. A total of 48 females were enrolled for this study, including 14 with osteoarthritis of one knee undergoing total knee arthroplasty (TKA) with an Osteonics prosthesis, 14 with osteoarthritis of one knee undergoing TKA with a Whiteside prosthesis, and 20 age-matched normal controls. The BMDs of both knees were measured before operation, and then at 3, 6 and 12 months after operation. The preliminary results demonstrate a significant progressive decrease of BMD in the distal femur of the operated knees after TKA, whereas the BMD of the non-operated knees remains stable. The ratio of BMD between the operated femur and the non-operated femur began to decrease 6 months after operation, and was most obvious at the end of the first year (ranging from 7% to 27%). Further investigation is essential to determine the clinical significance of this loss of periprosthetic bone.