gms | German Medical Science

Introduction: Most people suffering from osteoporosis are undiagnosed: the first osteoporotic fracture strikes an untreated organism. Therefore implant fixation often fails and bone healing is disturbed. In this basic research project, we explore possibilities to improve the quality of the osteopenic bone immediately after a fracture to avoid these complications.

Material and methods: Thirty-six female rats, which developed osteoporosis within ten weeks duration after ovariectomy (OVX), underwent a standardized metaphyseal osteotomy. The rats were divided into three groups, which received raloxifene (R:2.02mg/d R) or estrogen (E:0.09 mg/d), orally, or soyfree food (SF) only. During fracture healing the rats were subcutaneously injected with fluorescent agents to visualize the process of bone formation. Bones were analyzed using a three-point bending test, histological sections and microradiographs.

Results: Raloxifene and estrogen have exerted anabolic effects on the trabecular bone. Both substances induced fracture healing mainly via endosteal callus formation (R:2.08±0.66mm², E:2.02±0.75 mm² vs. SF:1.78±0.74mm²). Due to early bridging and advanced fracture healing, less bone occurred in the later stages after application of test substances. The biomechanical features determined by the Yield load of R- (100.3±28.4N) were at the level of E-treated bone (93.8±29.7N) being higher in both comparing to the osteoporotic bones (SF: 76.4±18.8N).

Conclusion: Raloxifene and estrogen had supporting effects in the therapy of fractures of osteoporotic bone. They improved not only the bone, but also the callus structure. Despite the small callus formation, raloxifene- and estrogen-treated bone had very good mechanical properties so that the risk of recurring (micro-)fracturing was significantly lower than in untreated osteoporotic bone.