Purpose: Bone remodelling and osteolysis around total hip prostheses remains an ineluctable corollary of prosthetic loosening. Alendronate (biphosphonate) has proven its efficacy for the treatment of osteoporosis of the lumbar spine and the femoral neck. There has been some in vitro work pointing out its contribution to the inhibition of osteolysis induced by particles. One in vivo study has demonstrated its interest in prevention of osteolysis around non-cemented total hip arthroplasties. The purpose of our work was to study the efficacy of this drug in the prevention of periprosthetic osteolysis around cemented total hip arthroplasties using biphotonic absortiometry (DPX).

Material and methods: The series included 38 patients who underwent unilateral total hip arthroplasty for degenerative hip disease. After double blinded randomisation, 20 patients were given 10 mg Alendronate per day with 600 mg calcium and 18 patients were given a placebo with 600 mg calcium for two years. All patients were followed with standard x-rays and DPX of the operated hip. Examinations were performed on the fourth postoperative day and on the third, sixth, twelveth and twenty-fourth postoperative month. The analysis concerned the periprosthetic zones defined by Gruen.

Results: DPX demonstrated significant reduction in bone mineral density (BMD) in all patients included in the study. This reduction was the same for the two groups early in the study and reached a maximum at three months; a divergence was observed thereafter. For the placebo group, the loss reached a plateau up to the sixth month after which the BMD started to rise progressively remaining at 12.7% reduction at two years (p< 0.002). In the ALN group, there was no plateau, BMD increased directly to reach 6.9% bone loss at two years (p< 0.003).

Discussion:The use of Alendronate enabled a significant reduction of periprosthetic bone loss at two years post-op. Our results are the first to our knowledge demonstrating a beneficial effect in vivo of the use of Alen-dronate on bone behaviour around cemented total hip arthroplasties.

Conclusion: Taking into account the short follow-up in this series, and its small size, other studies are indispensable to confirm this beneficial effect in vivo. The action of Alendronate could facilitate revision surgery by preserving bone stock.