The Effect of Alendronate on Bone Mineral Density in the Distal Part of the Femur and Proximal Part of the Tibia After Total Knee Arthroplasty

Background: Bone mineral density around the knee is related to the mechanical properties of bone. Alendronate has been shown to be effective for the treatment of osteoporosis and for reducing the rate of osteoporotic fractures. The purpose of the present study was to investigate the effect of alendronate on bone mineral density in the distal part of the femur and proximal part of the tibia after total knee arthroplasty in women.

Methods: Ninety-six women with an average age of seventy years who were undergoing total knee arthroplasty were randomly divided into two groups. Patients in the study group received oral alendronate at a dose of 10 mg/day for six months, whereas patients in the control group did not. The bone mineral density in the distal part of the femur and proximal part of the tibia was determined preoperatively and at six and twelve months postoperatively.

Results: In the control group, the bone mineral density showed significant decreases of 13.8% (p < 0.001) and 7.8% (p = 0.003) in the distal part of the femur and of 6.5% (p = 0.002) and 3.6% (p = 0.141) in the proximal part of the tibia at six and twelve months, respectively. In the study group, however, the bone mineral density showed significant increases of 10.0% (p = 0.010) and 1.9% (p = 0.049) in the distal part of the femur and of 9.4% (p < 0.001) and 5.4% (p = 0.032) in the proximal part of the tibia at six and twelve months, respectively. The overall differences in bone mineral density between the study and control groups were significant (p = 0.011 for the proximal part of the tibia, and p = 0.033 for the distal part of the femur).

Conclusions: We found significant postoperative decreases in bone mineral density in the distal part of the femur and proximal part of the tibia in women who had undergone total knee arthroplasty. Oral administration of alendronate for six months postoperatively significantly improved the bone mineral density. While the clinical benefits of alendronate after total knee arthroplasty remain unproven and the duration of follow-up in the present study was quite short, the improvement in bone mineral density may have a clinically important effect on prosthetic fixation and the rate of periprosthetic fractures after total knee arthroplasty.

Level of Evidence: Therapeutic study, Level I-1a (randomized controlled trial [significant difference]). See Instructions to Authors for a complete description of levels of evidence.