Caisson disease of bone: a study of the Göttingen mini-pig as an animal model.

Investigation of the exact aetiology, early diagnosis and prevention of caisson disease of bone has been hindered by the inability to produce, by the use of realistic compression/decompression exposures, truly comparable lesions in animals. Four Gottingen mini-pigs were subjected to repeated exposures to pressures of 27 p.s.i.g. for 6 h over a period of 9 months and decompressed according to standard tables. Two mini-pigs acted as controls. In one animal radiological changes were recognised in the left lower femoral shaft 19 weeks after the exposures were started and subsequent examination of that bone confirmed the presence, at that site, of a lesion which macroscopically and microscopically resembled, in every way, the appearances of those seen in the shafts of long bones in man. It is concluded therefore that, properly used, the mini-pig may be a suitable animal model for the study of this condition in man.

Aseptic necrosis of bone in a compressed air worker.

This paper reports a detailed examination of three lesions of aseptic necrosis of bone occurring in a man who had worked in compressed air eleven years previously. Although two of the lesions were juxta-articular, in neither had the bone collapsed. Histology of only one similar lesion is reported in the literature (McCallum et al. 1966). Necropsy material is considered, together with radiographs and bone scans of the same lesions taken four years earlier. Similar changes have been shown to occur in commercial divers. On the evidence of this case it becomes clear that radiography is limited in its use and that bone scans as an indicator of repair may be open to misinterpretation. There may be a place for operation before the onset of symptoms in these cases of aseptic bone necrosis.

Abnormal maturation of elastic fibres in the atherosclerotic intima.

It is probable that the conditions obtaining during cellular proliferation occurring as a result of damage to the vessel wall will not be at optimum level. The amino oxidase, lysyl oxidase, is copper-dependent and is required for proper cross-linkage in the maturing fibre. Elastic tissue in blood vessels is normally produced by smooth muscle cells and in circumstances where other cells derived from the blood are involved the production of fibres and ground substance may be altered. Orcein staining alone, or after oxidation with oxone, shows different tinctorial affinities for the fibres in the thickened intima and may indicate some departure from normality in their make-up.