RISEDRONATE TREATMENT DOES NOT INCREASE MICRODAMAGE IN THE CANINE FEMORAL-NECK

Cortical and trabecular bone from the femoral neck of 24 adult female beagle dogs was examined for microdamage following 2 years of treatmen t with risedronate (NE-58095), Specimens of the femoral neck, sectione d between the femoral head and the intertrochanteric groove, were bulk stained in 1% basic fuchsin in graded alcohols and embedded in methyl methacrylate. Five transverse sections of 100 mu m from each specimen were examined for microdamage and measurement of cortical and trabecul ar area, and three sections from each specimen were measured for calcu lation of trabecular and cortical bone activation frequency (Ac.f) and bone formation rate (BFR/BV) in the superior and anterior regions of the femoral neck. Although no statistical differences were observed am ong groups for numerical density or length of microcracks, Kruskal-Wal lis analysis showed differences among groups for both cortical and tra becular bone area (p < 0.05), Ac.f was significantly lower in both cor tical bone (p < 0.05) and trabecular bone (p < 0.005) of the femoral n eck at all dosage levels, No significant difference was observed among groups for trabecular mean wall thickness, The hypothesis that microd amage accumulation increases following reduction in Ac.f was not suppo rted for the canine femoral neck in this experiment, This result could be explained by the fact that microdamage does not accumulate followi ng treatment; that transient increases in microdamage at the beginning of the study period had been repaired; or finally, that the canine fe moral neck does not reflect weightbearing conditions of clinical relev ance to humans for assessment of microdamage.