Distal Femoral Bone Density Following Total Knee Arthroplasty

Abstract

The bone mineral density (BMD) in the distal femur after total knee arthroplasty (TKA) was measured in 78 patients, including 68 women and 10 men. The ages at operation ranged from 52 to 81 years (mean 66.8 years). Among them, 13 patients received Miller-Galante (Zimmer) prosthesis TKA; 38 received the Osteonics (Stryker) TKA, 9 received the Porous Coated Anatomic (PCA) (Howmedica) TKA, and 18 received the Whiteside (Dow Corning) TKA. The average time of BMD measurement was 10.2 months postoperatively (range 2–62 months). The average period for those patients receiving the Miller-Galante TKA was 35.7 months; for Osteonics TKA, 6.9 months; for PCA TKA, 26.8 months; and for Whiteside TKA, 6.6 months. The BMDs of both knees were measured with a densitometer. The preliminary results demonstrated a significant decrease of the BMD in the supracondylar areas of the operated knees (for medullary areas only in the anteroposterior view, 0.53 ± 0.13g/cm2 versus 0.57 ± 0.14g/cm2, P < 0.01; for medullary/cortical areas, 0.60 ± 0.13g/cm2 versus 0.65 ± 0.14g/cm2, P < 0.001; for medullary areas only in the lateral view, 0.71 ± 0.22 g/cm2 versus 0.79 ± 0.21 g/cm2, P < 0.0001; for medullary/cortical areas, 0.78 ± 0.17g/cm2 versus 0.87 ± 0.16g/cm2, P < 0.0001). The tendency of BMD to decrease was similar in both genders. The decrease in BMD was most obvious in the 1st year postoperatively and improved thereafter. These results revealed a significant decrease in BMD of the distal femur after TKA in the 1st postoperative year. The possibility of supracondylar fracture after TKA may be related to local osteoporosis. Further investigation is essential to evaluate the clinical significance of the decrease in periprosthetic bone.