Periprosthetic
osteolysis and aseptic loosening of
total joint replacements are believed to be initiated often by abnormal
bone resorption induced by prosthetic wear debris.
Bisphosphonates can inhibit
bone resorption and have been successfully used clinically to treat
osteoporosis and Paget's disease. In a recent study it also was shown that a third generation
bisphosphonate (
alendronate) is effective in preventing wear debris-induced periprosthetic
osteolysis. Since inhibition of
bone resorption by
alendronate may disrupt the delicate balance between
bone resorption and formation in normal bone remodeling, it is possible that continuous
alendronate therapy may have an adverse effect on the biomechanical properties of bone. Thus the purpose of the present study was to examine the effects of systemic
alendronate administration on the biomechanical properties of normal bone using a canine
total hip arthroplasty model. We evaluated the biomechanical properties of femora from canines that had received
total hip replacements on one side and had been given oral
alendronate daily for 23 weeks. The biomechanical properties assessed were fracture toughness, elastic modulus, tensile strength, microhardness, porosity, and weight fractions of the
mineral and organic phases of bone. Also, bone microstructure was examined using optical microscopy. Our results indicate that in the short term
alendronate therapy does not have any adverse effects on the intrinsic biomechanical properties of canine bone. However, the long-term effects of
alendronate therapy still need to be investigated.