Experimental limb lengthening by epiphyseal distraction.

Kirshner wires were placed either side of the right distal femoral epiphysis and a constant tension device applied a distracting force across the plate in rabbits. Growth increase was measured between the wires and found to be about 150% greater than the concurrent normal growth between 2 control (undistracted) wires on the left; such growth increase can occur in the absence of fracturing. The forces required to do this were between 1/5 and 1/10 of those shown to cause fracturing in vitro. The growth increase was shown to be associated with hyperplasia and hypertrophy of the plate, as well as an increased rate of cell division and sulfated polysaccharide synthesis. This was in turn shown to be associated with an increase in new bone formation.