Characterize the effects of alendronate (ALN) on the repair process of the osteonecrotic femoral head as well as the development of secondary osteoarthritis in the ipsilateral hip in an established experimental model of osteonecrosis.
Osteonecrosis of the femoral head was induced surgically in 60 adult, male New Zealand white rabbits. Animals were randomized in two placebo- (saline) and two treatment-groups (ALN 150 microg/kg/day S.C., 3x per wk) and were euthanized at 6 and 12 months post-operatively. Contralateral hip was used as control. Micro-Quantitative-CT (microQCT) analysis as well as histological assessment was performed in the femoral head and the acetabulum. Mankin Score was used to assess cartilage degeneration in the acetabulum.
Repair in the osteonecrotic femoral head in the placebo group led to a significantly increased bone volume fraction (BVF) and volumetric bone mineral density (vBMD) in the trabecular region and to an increase in porosity in the cortical and subchondral region when compared to the normal femoral head on the contralateral side. ALN treatment significantly further increased BVF and vBMD in the trabecular region, and significantly reduced porosity and increased vBMD in the necrotic subchondral and cortical bone when compared to placebo. ALN led to a significant increase in vBMD in the subchondral region of the osteoarthritic acetabulum as well as to a significant reduction in articular cartilage degeneration.
Inhibition of bone resorption by ALN treatment during repair of the osteonecrotic femoral head significantly increased bone mass in the trabecular region of the femoral head, inhibited subchondral resorption and reduced cartilage degeneration in the acetabulum.