Cranial vault expansion using transcutaneously activated magnetic implants.

The technique of distraction osteogenesis has not been widely used in the treatment of problems of the head and face because of the need for external fixators. By using magnetic, rather than mechanical, forces to drive bone movement we hope to expand the applications of the technique to include the treatment of cranial vault deformities. Thirty immature rabbits were studied. Twenty-six of the rabbits underwent operations. Each of the 26 had 2 magnets fixed to its skull: one on the left parietal bone and one on the right parietal bone. Incomplete circumferential osteotomies were then performed around each magnet on 13 of the rabbits. A head frame was attached to each animal. Head frames without magnets were placed on 6 of the rabbits (3 with osteotomy, 3 without osteotomy) while 20 of the animals (10 with osteotomy, 10 without osteotomy) had 2 magnets mounted on the frames which were of opposite polarity to those implanted. The remaining 4 rabbits served as nonoperative controls. Six weeks later all of the animals were sacrificed. There were significant differences in the cranial volumes and contours between the groups of animals. Many of the differences were increased by coincident osteotomy. Associated histologic findings are described.

Cranial vault moulding by the transcutaneous activation of implanted magnets.

The technique of distraction osteogenesis has not been widely used in the treatment of injuries of the head and face because of the need for external fixators. By using magnetic, rather than mechanical, forces to drive bone movement we hope to expand the applications of the technique to include the treatment of cranial vault deformities. Fifteen immature rabbits were studied. When they were 6 weeks old each had a magnet fixed to their left parietal bone. A head frame was attached and a magnet of either the opposite polarity to, (group 1), or the same polarity as, (group 2), the implanted magnet was mounted on the frame. Five weeks later the rabbits were sacrificed. There were significant differences in parietal skull width and in several measures of skull length between the animals in group 1 and those in group 2. These results demonstrate that, in this model, magnetic forces can be used to modify skull growth.