The Vascular Contribution to Osteogenesis. v. the Vasculature Supplying the Epiphysial Cartilage in Rachitic Rats.

lii previous papers of this series (Trueta and Amato 1960, Trueta and Trias 1961) experiments were described in which the effect of a decrease or total suppression of the blood to either one or other side of the epiphysial cartilage was investigated. These experiments showed that the only source of nourishment of the growth cartilage was the blood of the epiphysial vessels. It was also demonstrated that reducing the epiphysial blood supply led sometimes to a slight and transient thickening of the growth cartilage in areas made experimentally hypoxic, whereas in those parts persistently deprived of blood flow, first the cells of the germinal and proliferative segments, and ultimately the whole of the cell columns, became seriously damaged and finally disintegrated (Trueta and Amato 1960). When the role of the metaphysial vessels was studied it was found that they played little or no part in the nourishment of the cartilage cells but that, on the contrary, the presence of these vessels was necessary to enable the hypertrophic cells of the columns to be removed in the normal process of growth. Consequently, when the metaphysial vessels were interrupted, no calcification occurred and the cartilage cells continued in their hypertrophic phase and did not disintegrate. With this cell preservation the cartilage thickened, taking on histological characteristics resembling those of rickets ; if revascularisation was allowed the rachitic picture was rapidly reversed. These findings suggested a rigid sequence of events in the process of epiphysial growth following cell division and cell hypertrophy thus : pericellular calcification, vascular invasion and bone formation. It was thus of interest to investigate the part played by calcification in the preparation of the vascular advance. Calcification was prevented by withholding the necessary fat-soluble vitamins.