A Comparison of the Effects of Alendronate and Alfacalcidol on Bone Mineral Density Around the Femoral Implant and in the Lumbar Spine After Total Hip Arthroplasty

Abstract

Several previous studies have demonstrated that bone mineral density loss around femoral implants is common, particularly in the proximal part of the femur, soon after total hip arthroplasty. The purpose of the present study was to compare the effects of alendronate and alfacalcidol on bone mineral density loss around the femoral implant and in the lumbar spine after total hip arthroplasty. The present study included sixty patients with osteoarthritis of the hip who had undergone a primary cementless total hip arthroplasty. We assigned these individuals to treatment with alendronate (n = 20), alfacalcidol (n = 18), or no medication (n = 22). Periprosthetic and lumbar spine bone mineral density was measured one week after surgery, and biochemical markers (bone-specific alkaline phosphatase and serum N-terminal telopeptides of type-1 collagen) were measured before surgery as a reference baseline. Subsequent measurements were performed at twelve, twenty-four, and forty-eight weeks after surgery. The periprosthetic measurement area in the femur was defined as Regions 1 to 7, which are consecutively located around the implant from the greater trochanter to the lesser trochanter and calcar. Bone mineral density in the alendronate group was maintained in all regions. In the alfacalcidol and no-medication groups, bone mineral density in Region 7 was lower than in Regions 3 to 6 throughout the study period (p < 0.0001 as a result of repeated measures analysis of variance). Bone mineral density in the lumbar spine in the alendronate and alfacalcidol groups was higher than in the no-medication group at forty-eight weeks. The serum level of N-terminal telopeptides of type-1 collagen in the alendronate group was lower than that in the no-medication group throughout the study period (p = 0.003, 0.02 and 0.005). Alendronate prevented bone mineral density loss around femoral implants, particularly in Region 7 (calcar), but alfacalcidol did not show any effects in any regions. However, bone mineral density losses in the lumbar spine were effectively prevented by either alendronate or alfacalcidol.