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.