Background: Bone mineral density decreases after total knee
arthroplasty and is believed to affect prosthetic fixation. Treatment with
alendronate has been shown to improve short-term bone mineral density after
total knee arthroplasty; however, the long-term effects of this therapy are
unknown. The purpose of this study was to evaluate the long-term effects of a
six-month course of alendronate on bone mineral density after total knee
Methods: Sixty patients were randomly assigned to receive either
oral alendronate at a dosage of 10 mg/day for six months or no alendronate.
The bone mineral density in the distal aspect of the femur and the proximal
aspect of the tibia was measured preoperatively and at six, twelve, and
thirty-six months after total knee arthroplasty.
Results: Fifty-four patients (twenty-nine in the alendronate group
and twenty-five in the control group) completed the study. The alendronate
group showed significant increases in bone mineral density in the distal
aspect of the femur compared with the controls at six months (+4.8% and
—14.2%, respectively; p < 0.01) and twelve months (+1.6% and
—11.5%, respectively; p < 0.01). No significant difference in bone
mineral density was detected between the groups at thirty-six months
(—3.9% and —12.2%, respectively; p = 0.08). Similar trends in bone
mineral density changes were also observed in the proximal aspect of the
Conclusions: A six-month course of alendronate initially increased
bone mineral density at six and twelve months after total knee arthroplasty,
but no difference was noted after thirty-six months. The effect of alendronate
on bone mineral density after total knee arthroplasty may be limited after
discontinuation of therapy.
Level of Evidence: Therapeutic Level I. See Instructions
to Authors for a complete description of levels of evidence.