ALENDRONATE REDUCES PERIPROSTHETIC BONE LOSS AFTER UNCEMENTED PRIMARY TOTAL HIP ARTHROPLASTY - A 5-YEAR FOLLOW-UP OF 16 PATIENTS

Background and Aims: Periprosthetic bone loss, especially in the proximal part of the femur, is common after cemented and uncemented total hip arthroplasty (THA). Shortterm studies suggest that bisphosponates can minimize this bone loss related to stress-shielding phenomenon. The aim of the present randomized study was to investigate whether the positive effect of a 6 months alendronate treatment postoperatively still exists at five-year follow up. Materials and Methods: Sixteen uncemented primary THA patients were randomized to receive either 10mg alendronate + 500 mg calcium (n = 7) or 500 mg calcium only (n = 9) daily for 6 months postoperatively. Periprosthetic bone mineral density (BMD) was measured with the dual X-ray absorptiometry (DXA) postoperatively and at 6, 12, 24, 36 and 60 months follow-up. Results: At the 5-year follow up, the calcium group showed mean BMD decreases of 23.1% (SD 14.6) in the proximal part of the femur (prROI) and 9.6% (SD 14.9) in total femoral regions of interest (totROI). In the alendronate group the corresponding BMD decreases were 13.6% (SD 19.0) and 3.9% (SD 7.6) respectively. The positive effect of alendronate was already demonstrated during the first six months postoperatively. Subsequently the bone loss was equal in both groups, and the 5-year BMD changes were not significantly different between the groups. Conclusions: Alendronate seems to decrease early periprosthetic bone loss after arthroplasty but this pilot study could not provide enough evidence that the positive effect noted in the early postoperative period is still maintained 5 years after the operation.