Bone
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We modified the noninvasive, in vivo technique for strain application in the tibiae of rats (Turner et al., Bone 12:73-79, 1991). The original model applies four-point bending to right tibiae via an open-loop, stepper-motor-driven spring linkage. Depending on the magnitude of applied load, the model produces new bone formation at periosteal (Ps) or endocortical surfaces (Ec. ⋯ Bending strains above a loading threshold of 40 N increased Ec lamellar bone formation rate, bone forming surface, and mineral apposition rate with a dose response similar to that reported by Turner et al. (J Bone Miner Res 9:87-97, 1994). We conclude that the modified loading system offers precision for applied loads of between 0 and 70 N, versatility in the selection of loading rates up to 20 Hz, and a reproducible bone formation response in the rat tibia. Adjustment of the loader also enables study of mechanical usage in murine tibia, an advantage with respect to the increasing variety of transgenic strains available in bone and mineral research.