[Healing fibular bone fracture in rats during extended suspension ]

Healing of peroneal bone fracture was studied histologically and histomorphologically in rats exposed to a 30-d tail-suspension. To fracture bones, anesthetized rats were operated on day 15 of suspension. Hind limb deprivation of the support loading for a period of 30 days minimizes healing processes in fractured peroneal bones as was evidenced by undersized callus and lowered strength of bone consolidation. Mass-metric and histomorphometric investigations showed that, as compared with the control, on day 15 of regeneration the callous mass and volume in the suspended rats were by 34% and 35% less, respectively; the newly formed spongy bone, the fibrous-cartilaginous tissue and the cartilage were by 44%, 70% and 86% smaller in size, respectively. Nonetheless, healing dynamics in the suspended rats was not disturbed and the calluses were on the same phase of development as in the control, which is attested by similarity of the histological picture. Based on the comparative retrospective analysis of fracture healing in rats in 15- and 30-d experiments, the extended (30-d) suspension did not further impede the post-traumatic bone regeneration. It is suggested that minimization of bone fracture healing during the 15-d suspension was conditioned not only by inhibition of the growth hormone production but also by an acute stress reaction in the early period of adaptation.