Absence of positive effect of black cohosh (Cimicifuga racemosa) on fracture healing in osteopenic rodent model.

The healing of predominantly metaphyseal fractures in postmenopausal osteoporosis is delayed and comparatively poor. Due to the potential side effects of HRT, natural alternatives are appealing. The aim of this study was to determine whether Cimicifuga racemosa extract BNO 1055 improves metaphyseal fracture healing in severe osteopenic bone in rats. Thirty-three 12-week-old female rats developed severe osteopenia during 10 weeks after ovariectomy. After metaphyseal tibial-osteotomy and standardized T-plate-osteosynthesis, the healing periods in ovariectomized rats (C), 17-α-estradiol (E) and Cimicifuga racemosa (CR) supplemented diets were assessed for 35 days. Changes in callus morphology were evaluated qualitatively by biomechanical testing and quantitatively in microradiographies and fluorochrome-labeled histological sections. The CR-supplementation slightly improved callus quality and trabecular bone formation. It significantly enhanced the endosteal callus density compared to C group (Cl.Dn.e C: 59.08 ± 21.89, E: 45.95 ± 18.39, CR: 60.85 ± 18.66*), though most of the other morphological parameters examined showed no improvement. The time course of fracture healing did not change due to CR. Estrogen-supplementation enhanced the biomechanical properties of the fracture site. Trabecular bone was improved indicating the physiological endosteal healing process. The CR-supplementation did not exhibit positive effects in severe (senile) osteopenic fracture healing as seen in early (postmenopausal) osteoporosis in rats. Callus formation was slightly improved under CR. Estrogen improved fracture healing in severe osteopenic bone, while the extent of callus formation played a minor role.