Short-term zoledronic acid reduces trabecular bone remodeling in dogs

The effects of zoledronic acid, a bisphosphonate, on the trabecular bone remodeling (TBR) of the mandibular condyle are unknown. The objectives of this study were to quantify and compare TBR in the mandibular condyle and vertebrae of 2- to 3-yr-old dogs and to evaluate the effects of short-term zoledronic acid on TBR. Bone samples from two, age-matched groups of dogs [seven dogs were given no treatment (NT group) and seven dogs were treated with four total infusions of zoledronic acid administered monthly (ZOL group)] were analyzed using histomorphometry. Trabecular bone remodeling and microarchitecture were quantified and analyzed statistically. Physiologic TBR, quantified in the NT group, was significantly higher (more than sixfold) in the vertebrae than in the mandibular condyle. Trabecular bone remodeling in the vertebrae of dogs of the ZOL group was 96% lower than in dogs of the NT group. By contrast, TBR in the mandibular condyle of dogs in the ZOL group was statistically equivalent to that of dogs in the NT group. Our results demonstrate that the physiological TBR in aged dogs is vastly different in the mandibular condyle compared to that in the vertebra. A higher level of physiologic TBR in the vertebra than in the mandibular condyle results in greater reduction of TBR in response to short-term treatment with zoledronic acid.