THE EFFECTS OF GUIDED TISSUE REGENERATION AND FIXATION TECHNIQUE ON OSSEOUS WOUND-HEALING IN RABBIT ZYGOMATIC ARCH OSTEOTOMIES

The development of fibrous nonunions after craniofacial surgery is tho ught to result from an interaction of biomechanical stress and the dif ferential migration of various tissue types into the wound site during healing. The present study is designed to test this hypothesis throug h the manipulation of guided tissue regeneration and osteotomy fixatio n techniques in an experimental rabbit model. Bilateral, critical size (5 mm) vertical osteotomies (n = 32) were produced in the zygomatic a rches of eight adult rabbits. The mobile bony segments were fixed rigi dly or nonrigidly using bone microplates and screws or osteosynthetic wires. The defects were then covered with a resorbable collagen membra ne or left uncovered. The rabbits were followed for 4 weeks with seria l dorsoventral cephalographs and the zygomatic arches harvested for hi stological analysis. Cephalometric results revealed significantly (p < 0.001) increased bone growth in the margins of the defects covered wi th the collagen membrane; however, no significant (p > 0.05) differenc es were noted between fixation techniques. Histological analysis revea led that defects fixed rigidly and covered by the membrane showed the most rapid and organized osseous wound healing, followed by the defect s that were fixed nonrigidly and membrane covered. The defects not cov ered by the collagen membrane showed invasion by fibroblasts resulting in fibrous nonunions. These results demonstrate the efficacy of guide d tissue regeneration with a resorbable collagen membrane in preventin g fibrous tissue ingrowth in large bony defects. The addition of rigid fixation at a potentially mobile site appeared to enhance bony trabec ular organization but not the osteogenic rate in this rabbit model.