Avascular necrosis of the mandibular ramus in the baboon (Papio ursinus) following orthognathic surgery.

The maintenance of an adequate blood supply to the mandible following orthognathic surgery is of extreme importance if satisfactory healing is to be achieved. With this object in mind, this study was undertaken to assess the effects of disrupting the blood supply of the baboon mandible by means of L- and C-osteotomies. Ten adolescent baboons of the species Papio ursinus were used as the experimental animals for the study. On five of them a modified vertical subsigmoid osteotomy (L-osteotomy) and on five a C-osteotomy of the mandibular ramus were performed. In each experimental animal the osteotomy was undertaken on one side of the mandible only, the other side serving as a control. After a postoperative period of 14 days the animals were killed, the entire mandible removed, and the tissues prepared for examination with the light microscope. Histometric analysis revealed a significant degree of avascular necrosis in certain areas of the proximal or condylar fragments and to a lesser extent in the distal fragment. Avascular necrosis was also seen on the control side. It was also revealed that the periosteum and attached muscles of mastication play a role in the blood supply of the mandible and that the additional attachment of the temporalis muscle to the proximal fragment is of no advantage in enhancing the vascularity of that fragment.