We evaluated the effects of suppressed bone remodeling caused by bisphosphonate on microdamage accumulation and degree of mineralization of bone (DMB) for the dog rib in two independent studies. Study 1: 36 female beagles, 1-2 years old, were treated daily for 1 year with saline vehicle, risedronate at 0.5 mg/kg/day, or alendronate at 1.0 mg/kg/day. Study 2: 29 beagles, 1 year old, were given lactose, or incadronate at 0.3 mg/kg/day or 0.6 mg/kg/day for 3 years. In both studies, the ninth rib was harvested. Intracortical remodeling was significantly suppressed following either 1 year or 3 years of bisphosphonate treatment without impairment of primary mineralization, although the remodeling rate was obviously lower in study 2 than in study 1 because of the aging of animals. Microdamage accumulation was significantly increased following any bisphosphonate treatment in response to the extent of remodeling suppression. One-year treatment with risedronate or alendronate did not significantly affect the mean DMB or osteonal distribution based on DMB. In contrast, mean DMB was significantly increased following 3 years of incadronate treatments, and osteonal distributions based on DMB showed a dose-dependent shift toward the higher values in incadronate-treated animals when compared with controls. Our results demonstrated that DMB was increased following only 3 years but not 1 year of bisphosphonate treatment. This finding suggests that suppressed remodeling induced by long-term bisphosphonate treatment increased DMB by increasing the population of old, highly mineralized osteons; however, the expression of this phenomenon depends on duration of the treatment because the secondary mineralization is a very slow process.
- Cortical bone
- Degree of mineralization
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Orthopedics and Sports Medicine