The response of the rat tibial growth plates to distal periosteal division.

The growth plate chondrocytes have been examined in the tibiae of normal immature rats and in similar rats after circumferential distal periosteal release. In control rats, calculation of the growth rate as the product of the rate of cell proliferation and the maximum hypertrophic cell height correlated with gross measurements. The labelling index also correlated with the calculated growth rate. During the period 28 to 46 days of age there was little change in the growth rate but a diminution in the height of the hypertrophic cells. Unilateral circumferential periosteal division produced bilateral increases in tibial growth rate and in the activity of both the proliferative and hypertrophic zones as part of the systemic response to the trauma. There was a 1% ipsilateral increase in tibial length, as compared to the contralateral side, which appeared to be related principally to an increase in the number of proliferative cells. This simple method of stimulating bone growth can usefully be undertaken at the same time as other operative procedures.