Growth potential of different zones of the growth plate-an experimental study in rabbits.

Despite clinical efforts to treat growth disturbances only little is known about the growth potential of the different zones of the growth plate. The aim of this study was to investigate the growth potential of different zones of the growth plate. A total of 20 New Zealand White rabbits were used for this experiment. The right and left ulna of each animal were used resulting in a total of 40 ulnae. Animals were assigned into five groups. In groups I and II resection of the metaphyseal (n = 12) or the epiphyseal (n = 6) segment of the growth plate was performed. In group III resection of the growth plate and re-implantation was performed (n = 6). In group IV the growth plate was resected and re-implanted after a 180° rotation (n = 6). Animals in group V served as controls. Histologic and radiologic examinations were performed to evaluate the growth process at 1, 2, 4, and 12 weeks following surgery. In group I, III, and IV temporary growth disturbance which was compensated within a short time was observed. Resection of the epiphyseal part resulted in growth arrest of the distal ulna in combination with normal growth of the radius which led to and valgus deformity of the limb. The results of this study indicate the importance of the reserve zone for the functioning of the growth plate.

The effect of drilling and screw fixation of the growth plate--an experimental study in rabbits.

Injury of the growth plate is a specific problem in traumatology and can cause limb deformity and length discrepancy as a result of growth arrest. The purpose of this study was to evaluate alterations of the growth plate after artificially created injuries. A total of 14 New Zealand White rabbits were used for this experiment. The right and left ulna of each animal was used resulting in a total of 28 ulnae. In six animals drill holes were driven into the growth plate either from the distal/epiphyseal side or from the proximal/metaphyseal side of the physis. In six animals a fracture of the distal ulna corresponding to a Salter-Harris fracture type IV was created. This fracture was fixed by screws from either the epiphyseal or the metaphyseal side. Two animals served as controls. Histologic and radiologic examinations were performed to evaluate the growth process at 1, 2, 4, and 12 weeks following surgery. Drilling or fixation of the growth plate from the metaphyseal side resulted in temporary growth disturbance which was compensated within a short time. In contrast fixation from the epiphyseal side caused severe growth disturbances. Based on our findings K-wires or screws should be inserted from the metaphyseal side and be placed in the center of the growth plate.