COMPARISON OF ALENDRONATE AND SODIUM-FLUORIDE EFFECTS ON CANCELLOUS AND CORTICAL BONE IN MINIPIGS - A ONE-YEAR STUDY

Fluoride stimulates trabecular bone formation, whereas bisphosphonates reduce bone resorption and turnover, Fracture prevention has not been convincingly demonstrated for either treatment so far, We compared th e effects of l-yr treatment of 9-mo-old minipigs with sodium fluoride (NaF, 2 mg/kg/d p.o.) or alendronate (ALN, 4 amino-1-hydroxybutylidene bisphosphonate monosodium, 1 mg/kg/d p.o.) on the biomechanical and h istomorphometric properties of pig bones, As expected, NaF increased a nd ALN decreased bone turnover, but in these normal animals neither ch anged mean bone volume, NaF reduced the strength of cancellous bone fr om the L4 vertebra, relative to control animals, and the stiffness (re sistance to deformation) of the femora, relative to the ALN group, In the ALN-treated animals, there was a strong positive correlation betwe en bone strength and L5 cancellous bone volume, but no such correlatio n was observed in the NaF group, Furthermore, the modulus (resistance to deformation of the tissue) was inversely related to NaF content and there was a relative decrease in bone strength above 0.25 mg NaF/g bo ne, Moreover, within the range of changes measured in this study, ther e was an inverse correlation between bone turnover, estimated as the p ercentage of osteoid surface, and modulus, These findings have relevan t implications regarding the use of these agents for osteoporosis ther apy.