INTRODUCTION: The purpose of this study was to investigate morphological changes of trabecular bone in the lumbar vertebral bone of experimentally‐induced osteoporotic sheep using backscattered scanning electron microscopy (BS‐SEM).
METHODS: Osteoporosis was induced in five mature ewes using a combination of bilateral ovariectomy, dexamethasone injection and low calcium diet for six months. Four sheep were used as controls. All animals were humanely killed after 6 months and trabecular bone samples from the L2 vertebrae were collected and analysed using BS‐SEM. The degree/pattern of mineralisation and the density, size, aspect ratio and area of osteocyte lacunae were examined. Differences between control and osteoporotic sheep were tested using Student's t‐test with p < 0.05 considered significant.
RESULTS: Relative to the control animals trabeculae from osteoporotic sheep vertebrae were 50 % thinner (p < 0.05) with 5.8 fold more erosion cavities on the surface (p < 0.05). The intensity of electron transmission was less in the osteoporotic group. Osteocyte lacuna density in the osteoporotic sheep was 25 % less than in the control sheep (p < 0.05). Neither the size nor the shape of the lacunae changed with induction of osteoporosis. Trabecular bone in the osteoporotic sheep was mainly woven compared with the more usual lamellar arrangement in the controls.
CONCLUSION: The observed increase in the number of eroded cavities on the surface of bone in osteoporotic sheep is likely due to delayed coupling of bone resorption and bone formation. The thinning of trabeculae may be associated with a reduction of bone mineral density. Alterations in the number, but not the size or shape, of osteocyte lacunae in lumbar vertebral trabeculae could be an important contributor to bone loss and bone quality in this experimental ovine model of osteoporosis.