Effects of black cohosh (Cimicifuga racemosa) and estrogen on metaphyseal fracture healing in the early stage of osteoporosis in ovariectomized rats.

Osteoporosis and its accompanying, predominantly metaphyseal, fractures are a major health problem. Black cohosh (Cimicifuga racemosa) and estrogen positively influence osteoporotic bone. Both substances may improve fracture healing in early osteoporosis as well. In 48 twelve-week-old ovariectomized or, respectively, sham-operated (SHAM) rats, a standardized metaphyseal tibia osteotomy with bridging T-plate fixation was performed. During the healing process of 35 days, rats received soy-free (SHAM, osteopenic C), estrogen- (E) or Cimicifuga racemosa- (CR) supplemented diets. After sacrifice, the callus formation was analyzed with regard to biomechanical quality, morphology, quantity, time course of new bone built and gene expression. CR induced a high rate of metaphyseal callus formation. The biomechanical properties and the amount of new callus formation indicated that fracture healing was still in progress. Therefore, gene expression of osteoblasts was comparatively high. Body weight and the trabecular structure were influenced little by CR. Estrogen improved the biomechanical properties of the callus. Resistance to microfracturing was significantly enhanced in the E group and even superior to SHAM. Remodeling of the callus formation had already begun. The trabecular network and the typical endosteal fracture healing were especially improved. Osteoporotic metaphyseal fracture healing was improved by estrogen more than by Cimicifuga racemosa. The process of fracture healing occurred nearly physiologically. The generation of callus formation was supported by Cimicifuga racemosa as well, but the five-week duration of application was too short for Cimicifuga racemosa to show its complete potential. Already-initiated Cimicifuga racemosa therapy for menopausal symptoms could be continued during fracture healing without hesitation.