Bone blood flow in the femora of anesthetized and conscious dogs in a chronic preparation, using the radioactive tracer microsphere method.

The radioactive tracer microsphere method is applicable to the study of the hemodynamics of bone. As observed previously by others, areas of predominantly cancellous bone produce higher blood flow measurements than do areas of predominantly cortical bone. Bone containing fatty marrow has lower blood flow rates than does bone containing hematopoietic marrow. Blood flow to the femoral neck was the greatest measured (26.74 +/- 1.95 ml/min/100 gm), while the diaphyseal region was the area with the lowest flow (4.67 +/- 0.46 ml/min/100 gm). There was no significant difference between consecutive measurements using up to five differently labeled radioactive microspheres. This enabled observations of the effects of an experimental procedure on bone blood flow in the same animal. Additionally, there was no statistically significant differences between regional blood flows measured 40 days apart in the same animal. Bone blood flow measurements were slightly lower in anesthetized than in conscious dogs. The RTM method is the one most suitable for the estimation of bone blood flow under either acute or chronic conditions.

Growth of the rat femur in diffusion chambers.

Growth in the length of 9-day-old rat femurs, isolated and cultivated in diffusion chambers, was studied for a limited period of 16 days. An increment of 40 per cent of the in vivo length was observed. It could be established that the elongation was due to chondral growth, of which 40 per cent occurred at the proximal and 60 per cent at the distal end of the bone during the 16 days of observation. When the trochanteric or the head epiphyses with their physeal plates were resected, no statistically significant loss in total length occurred. A small but statistically highly significant biphasic growth due to enchondral ossification was found. Resection of the trochanter produced a widening of the cervico-diaphyseal angle (valgisation) of an average of 11.2 degrees. The findings in this series of isolated femurs are --in a general way--similar to those observed in the living animal.