Vertebral blood flow and bone mineral density during long-term corticosteroid treatment -: An experimental study in immature pigs

Study Design. Bone mineral blood flow were measured in methylprednisolone treatment, Objectives. To investigate possible changes in bone mineral density and vertebral blood flow during longterm glucocorticoid treatment. Summary of Background Data. Steroid-induced vertebral osteonecrosis preferentially involves endplates and adjacent cancellous bone. The precise etiology of vertebral osteonecrosis during long-term glucocorticoid treatment is unknown. Methods. Twenty-four 10-week-old female Danish landrace sister pigs from 12 litters were treated in two groups. Twelve animals received oral methylprednisolone for 3 months at a daily dose of 100 mg. The 12 sister pigs received no steroid treatment and served as controls. Regional blood blow was measured by means of microspheres in predefined regions of the C6, T11, and L6 vertebrae. In vitro DEXA scanning of the L2-L4 vertebra was performed to assess bone mineral density. Results. Vertebral cancellous bone and endplate regional blood flow were decreased in the C6 and L6 vertebrae among corticosteroid-treated pigs compared with that of controls. Width-adjusted lumbar vertebral bone mineral density (g/cm(3)) was unchanged, whereas projec tional lumbar vertebral bone mineral density (g/cm(2)) was decreased in corticosteroid-treated pigs. Conclusions. Long-term methylprednisolone treatment decreases vertebral bone blood flow mainly in cancellous bone and endplates. This may be an important factor in the pathogenesis of osteonecrosis secondary to glucocorticoid treatment. Lumbar vertebral bone mineral density was unchanged in growing pigs on long-term glucocorticoid treatment when expressed as volumetric bone density. The effect of glucocorticoid treatment on vertebral bone mineral density appears to depend on whether it is expressed as projectional (g/cm2) or volumetric bone mineral density (g/cm3). Vertebral and longbone growth was reduced during methylprednisolone treatment.