Thus far, orthopedic research lacks a suitable animal model of osteoporosis. In OVX sheep, 6 months of steroid exposure reduced bone density and mechanical competence. Bone properties and bone formation did not recover for another 6 months. Therefore, steroid-treated OVX sheep may serve as a large animal model for osteopenic bone. Introduction:The purpose of this study was to explore the effects of glucocorticoid treatment on cancellous bone density, microarchitecture, biomechanics, and formation of new bone. Materials and Methods: Sixteen ovariectomized merino sheep received either a 6-month glucocorticoid treatment (GLU; 0.45 mg/kg methylprednisolone) or were left untreated (control). Cancellous bone biopsy specimens from the tibia were harvested 6 months after ovariectomy. After 12 months, the animals were killed, and biopsy specimens were obtained from the contralateral tibia and the lumbar spine. All biopsy specimens were scanned for apparent bone mineral density by peripheral quantitative computed tomography (pQCT) and tested mechanically in uniaxial compression. Three-dimensional bone reconstructions were obtained by microcomputed tomography. Formation of new bone was analyzed using histologies of the femoral condyles. Results: After 6 months, mineral density (Ϫ19%) and mechanical competence (Ϫ45%) were reduced by glucocorticoid treatment (p Ͻ 0.1). BV/TV (Ϫ21%; p Ͻ 0.01) and trabecular thickness (Ϫ20%; p ϭ 0.01) declined, whereas BS/BV increased (24%; p ϭ 0.01). After 12 months, mineral density (Ϫ33%) and mechanical properties (Ϫ55%) were reduced even more profoundly (p Ͻ 0.05). Also, the structural parameters (BS/BV and Tb.Th.) still seemed to be affected by glucocorticoid treatment (p Ͻ 0.05). New bone formation, assessed by measurement of osteoid surface, was markedly reduced (Ϫ63%, p Ͻ 0.1) by glucocorticoid treatment. The differences between groups were generally more pronounced at the tibia and the femur than at the spine. Conclusion: The effects of short-term high-dose steroid administration on bone mineral in this animal model were comparable with those observed in humans after long-term corticoid treatment. Reduction in bone quality and bone formation rate persisted after the cessation of steroid administration. Glucocorticoid treatment of ovariectomized sheep may therefore serve as a large animal model for steroid-induced osteopenia.

This study presents a new classification system for the different types of OSFs based on the origin and direction of the fracture plane. This new system was strongly influenced by the age at symptom onset. Such information is essential for successful open reduction and internal fixation by ensuring that fixation pressure is perpendicular to the fracture plane, which will avoid the recurrence of stress fractures. In addition, the prevalence of UCL injuries suggests that it is a major risk factor for the development of OSFs.

The purpose of this study was to determine the alterations in ovine trabecular bone induced by a combination of ovariectomy and steroid treatment. Twenty-four female skeletally mature Merino sheep were randomly assigned to ovariectomy alone (OVX), ovariectomy combined with glucocorticoid treatment for 6 months (OVX + GC), or no treatment (control). Biopsies of trabecular bone were harvested 6 and 12 months after the beginning of the study from the proximal tibia. The biopsies were scanned for apparent bone mineral density by quantitative computed tomography and were mechanically tested. Three-dimensional bone reconstructions were obtained by micro-computed tomography. Trabecular bone from the OVX + GC animals had a markedly reduced apparent bone mineral density (27% less than control), bone volume (34%), and elastic modulus (36%) at 6 months. At 12 months, the reductions in apparent bone mineral density (33%), bone volume (37%), and elastic modulus (62%) appeared to be even more pronounced. Ovariectomy alone did not result in a perceptible reduction in any parameter. The combination of ovariectomy and glucocorticoid treatment in sheep resulted in a successful induction of substantial loss of trabecular bone and thus may serve as a large-animal model for osteopenic trabecular bone for the development and testing of orthopedic implants and techniques under osteoporotic conditions.

No abstract