Osteoporosis influences the early period of fracture healing in a rat osteoporotic model

Osteoporotic fractures commonly occur in the elderly. Although current ther apies are aimed at the prevention and treatment of osteoporotic fractures, studies examing the fracture healing process in osteoporotic bone are limit ed. We produced an osteoporotic rat model by ovariectomy (ovx) and maintain ed a low calcium diet (LCD) in order to evaluate the influence of osteoporo sis on fracture healing. Callus formation and strength was monitored over a 3 week period by histological and biomechanical assessment. Data collected simultaneously on a group of rats undergoing sham surgery (sx) were used f or comparison. A 40% reduction in fracture callus cross-sectional area and a 23% reduction in bone mineral density in the healing femur of the ovx rat s was observed on day 21 following fracture as compared with the sx group ( p < 0.01), Biomechanical data from the healing femur of the ovx rats reveal ed a fivefold decrease in the energy required to break the fracture callus, a threefold decrease in peak failure load, a twofold decrease in stiffness and a threefold decrease in stress as compared with the sx group (p < 0.01 , respectively), Histomorphological analysis revealed a delay in fracture c allus healing with poor development of mature bone in the ovx rats. This st udy provides physical evidence of altered fracture healing in osteoporotic bone, which may have important implications in evaluating the effects of ne w treatments for osteoporosis on fracture healing. (C) 2001 by Elsevier Sci ence Inc. All rights reserved.