It is now clear that vitamin K1 is part of a biochemical cycle that is essential for the conversion of specific bone peptides into a form that can bind calcium. We have used a recently described procedure for assaying vitamin K1 in plasma to test the involvement of this vitamin in fracture healing. Markedly depressed circulating levels were found in patients with fractures and the time taken for this level to return to normal appeared to be influenced by the severity of the fracture.

Quantitative polarised light microscopy was applied to sections of unfixed, undecalcified bone taken at operation from patients with two types of proximal femoral fracture, subcapital and trochanteric. Specimens were also taken from the equivalent sites in otherwise normal subjects at autopsy, and from various other sites of traumatic fractures; these two latter groups acted as controls. Analysis of the 57 specimens disclosed changes in the nature of the bone at the site of subcapital fractures, namely the presence of relatively large crystals of hydroxyapatite and a change in the molecular orientation, but not total content, of the acidic proteoglycans of the bone matrix. Our results have confirmed and extended the findings of others on subcapital fractures, and have also shown very similar changes in the trochanteric fractures. It thus appears that the bony changes in the two types of proximal femoral fracture are not as different as has been suggested.

The aim of this study was to try to elucidate the increased susceptibility of the neck of femur to fracture. Quantitative polarised light microscopy has been applied to fresh, undecalcified sections of samples of bone taken from the site of fracture, in specimens taken at operation from patients with fractures of the femoral neck or osteoarthritic femoral heads or from the equivalent site from otherwise normal subjects at necropsy. In all 21 specimens of fractured necks of femur, but in none of the other specimens, relatively large crystals (up to 2.5 X 0.5 micrometres) were found close to the site of fracture; the properties of these crystals were compatible with their being apatite. Measurement of the natural birefringence of the collagen showed no difference in the orientation of the collagen in all three types of specimen. However, the orientation of acidic glycosaminoglycans, measured by the birefringence of alcian blue bound to these moieties, was 45 per cent lower in the specimens from fractured necks of femur than in the other specimens, even though the total content of acidic glycosaminoglycans was unchanged. Although the decreased orientation was most marked close to the site of fracture, it was still apparent 15 millimetres from that site. These changes were unlikely to be simply the sequelae of fracture since they were not found in traumatic fractures of other bones. Thus it is conceivable that changes in the orientation of the ground substance allow formation of relatively large crystals of apatite and that such crystals, in the microcrystalline mass of apatite, are the cause of the increased fragility of such bones.