Abstract

Background: Previous studies have reported bone loss in the proximal femur and contralateral knee during the first year after total knee arthroplasty. We studied whether this bone loss continues or is amended.

Methods: Thirty-eight patients who were scheduled for unilateral total knee arthroplasty were examined by dual-energy X-ray absorptiometry. Measurements of the contralateral knee and both hips were performed within a week of the operation then 1, 2 and 4 years postoperatively. The clinical status of the operated knee was recorded preoperatively and at each follow-up visit.

Results: The bone mineral density of the femoral neck and total femoral regions of interest of the affected side were significantly lower (6.6% and 5.1%, respectively) than the values obtained for the contralateral hip, and these values remained unchanged throughout the 4-year follow-up period. In the contralateral hip, there was a significant decrease in femoral neck bone mineral density (3.3%, p<0.01) and total femoral bone mineral density (3.0%, p<0.001) at the 4-year follow-up. In the contralateral knee, there was a significant reduction in bone mineral density of the femoral anterior metaphyseal (5.0%, p<0.001), total femoral metaphyseal (3.6%, p<0.001) and femoral diaphyseal (5.1%, p<0.001) regions of interest after 4 years when compared to baseline.

Conclusion: While total knee arthroplasty appears to stabilize affected side hip bone mineral density, it did not ameliorate the decrease in bone mineral density of the contralateral hip or contralateral distal femur during the 4 years after total knee arthroplasty.

Keywords: Total knee arthroplasty; Bone mineral density; Dual x-ray absorptiometry

Abbreviations: TKA: Total Knee Arthroplasty, OA: Osteoarthritis, BMD: Bone Mineral Density, DEXA: Dual X-ray Absorptiometry, BMI: Body Mass Index, AKS: American Knee Society Score, ROI: Region of Interest