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 thought to result from an interaction of biomechanical stress and the differential migration of various tissue types into the wound site during healing. The present study is designed to test this hypothesis through the manipulation of guided tissue regeneration and osteotomy fixation techniques in an experimental rabbit model. Bilateral, critical size (5 mm), vertical osteotomies (n = 32) were produced in the zygomatic arches of eight adult rabbits. The mobile bony segments were fixed rigidly or nonrigidly using bone microplates and screws or osteosynthetic wires. The defects were then covered with a resorbable collagen membrane or left uncovered. The rabbits were followed for 4 weeks with serial dorsoventral cephalographs and the zygomatic arches harvested for histological analysis. Cephalometric results revealed significantly (p < 0.001) increased bone growth in the margins of the defects covered with the collagen membrane; however, no significant (p > 0.05) differences were noted between fixation techniques. Histological analysis revealed that defects fixed rigidly and covered by the membrane showed the most rapid and organized osseous wound healing, followed by the defects that were fixed nonrigidly and membrane covered. The defects not covered by the collagen membrane showed invasion by fibroblasts resulting in fibrous nonunions. These results demonstrate the efficacy of guided tissue regeneration with a resorbable collagen membrane in preventing fibrous tissue ingrowth in large bony defects. The addition of rigid fixation at a potentially mobile site appeared to enhance bony trabecular organization but not the osteogenic rate in this rabbit model.

Traumatic rupture of the extensor pollicis longus tendon.

Rupture of the extensor pollicis longus tendon is rather rare, attributable in about half of all cases to rheumatoid arthritis affecting the wrist or to a Colles' fracture. In the remainder of cases, either a direct closed injury to the wrist or a hyperextension injury of the wrist is most often responsible. Far more unusual is a rotational injury which can cause complete avulsion of the EPL tendon at the musculotendinous junction. A delayed rupture is most probably caused by an avascular necrosis secondary to traumatic disruption of the mesotendon. Surgical correction of the injury is best accomplished by tendon transfer, using the extensor indicis proprius. Postoperative immobilization, hyperextension of the thumb, and adequate resting tension are all necessary to assure good return of function. Postoperatively, the patient may experience a slight decrease in extensor strength of the index finger which may or may not be accompanied by a minimal loss in extensor range.