The vascular repair of an experimental osteotomy held in an external fixator

The vascular repair of a lower tibial transverse osteotomy in the New Zealand white rabbit held in an external fixator was studied in three groups. In the first group, composed of 18 animals, the osteotomy gap was maintained throughout repair. Three animals were killed every two weeks up to 12 weeks postoperatively. In the second group, composed of three animals killed at six weeks, the fragments were brought into contact. In a third and similar group, the osteotomy was compressed. Plain roentgenograms were taken weekly, and intraarterial perfusion with Micropaque was performed when the animals were killed. Roentgenography using fine-grain film, microradiography, and histology were carried out on a midsagittal tibial slice. The results showed that following transverse osteotomy in which the gap was maintained, vascular union of the proximal and distal cortices and associated external callus masses had usually occurred by ten weeks postoperatively. However, an occasional hypovascular zone at the osteotomy site at 12 weeks was associated with fibrous delayed union. In contrast, when apposition or compression of the fragments was used, repair was accelerated, and cortical bone union was established at six weeks. Vascular union of the fragments occurred predominantly through the medullary vessels. The results emphasize the overriding clinical importance of abolition of a fracture gap to achieve rapid revascularization of a fracture and its union by bone.