原著

著者

Yasuhiro TOYOIZUMI, Masafumi MACHIDA* and Junnosuke RYU
Department of Orthopedic surgery, Nihon University School of Medicine
*Department of Orthopedic Surgery, National Hospital Organization, Murayama Medical Center

要旨

It is the most important to predict the risk of fractures commonly caused by osteoporosis which aresignificant cause of morbidity and mortality in the elderly population. It is well known that there is a relationshipbetween bone mineral density (BMD) and fracture risk. It is, however, difficult to assess fracture risk accurately byBMD measurement alone because of a large variability in BMD in patients both with and without existingfracture(s). In the present study, we investigated the effects of two bisphosphonates, alendronate and risedronate,on BMD and trabecular bone quality. Methods: Thirty bipedal 17-week-old rats which had undergone amputationof their forefeet and tail were ovariectomized and divided into 3 groups (N = 10 per group): one control (OVXgroup), and two treatment groups treated with either alendronate (ALN group) or with risedronate (RIS group).Another set of bipedal rats (n = 10) was prepared as a sham control (SHAM group). In each group, BMD wasmeasured in the lumbar spine and femur with dual-energy x-ray bone absorptiometry (DXA) and bone strength wasmeasured by three-point bending testing. Further, trabecular bone quality was assessed by micro-computed tomography(MicroCT) to give measurements of bone volume fraction, trabecular bone number, trabecular bone thickness,trabecular separation, trabecular bone pattern factor and structural model index. Results: BMD and the bonemechanical properties were (significantly) higher in the ALN and RIS groups than in the OVX group. MicroCTmeasurements showed that alendronate was more effective than risedronate in improving the trabecular bone qualityin the lumbar spine. Conclusion: The results demonstrate that both bisphosphonates are effective in increasingBMD and improving trabecular bone quality in bipedal rats. Alendronate is superior to risedronate in improving thevertebral trabecular bone microarchitecture.

keyword

alendronate, bone mineral density (BMD), microcomputed tomography, osteoporosis, risedronate