Experimentally Induced Dysbaric Osteonecrosis in Sheep : a Histopathological Analysis

Six mature female sheep were subjected to a series of 0.5, 1, 2 and 4 hour-hyperbaric exposures followed by acute decompressions over a 2.5 year period to simulate recreational and commercial diving.Sheep were euthanized 16 months after the last hyperbaric exposure. Roentgenographic examination of the sheep\u27s long bones revealed dysbaric osteonecrosis (DON) lesions in all the six sheep. Femurs fromtwo of the six sheep with DON were examined for pathological changes. A histopathological evaluation was performed on undecalcified sections of the femurs which showed widespread fatty marrow necrosisof the shafts. Proliferation of granulation tissue, calcification, and ossification were coexistent around the necrotic foci. Endosteal new bone formation also occurred. The significance of fatty marrownecrosis is discussed in comparison with human cases concerning the development and progression of DON