MICROANGIOGRAPHIC PATTERN OF BONE HEALING IN CANINE TIBIAL OSTEOTOMIES TREATED WITH TYPE-II EXTERNAL FIXATORS

The morphological aspects of the vascular response, which develops in the fracture-healing process of osteotomies treated with external fixa tors, were evaluated by means of microangiography. Bilateral transvers e midshaft osteotomies were performed in the tibiae of 16 dogs. The os teotomies were reduced by means of a Type II external skeletal fixator , and the clinical and radiographic courses were assessed weekly until the moment of euthanasia. Four dogs each were euthanatized at one, tw o, four and eight weeks postoperatively. After heparinization and euth anasia both femoral arteries were perfused with micronized barium sulp hate, and microangiograms were performed in decalcified mid-tibial sag ittal slices. Initial intramedullary revascularization as well as gap supply were already observed in some one-week microangiograms, and the y were well developed in all of the two-week microangiograms. A networ k of parallel extraosseous blood vessels, orientated perpendicularly t o the cortical surface, first appeared in the two-week microangiograms . Four weeks after the osteotomy, the extraosseous network showed its greatest degree of development whereas in the eight-week microangiogra ms most of the osteotomies showed only some traces of the above-mentio ned vascular reaction. It can be concluded that the microangiographic pattern developed in external fixated osteotomies shows many similarit ies with these described in experimental fractures, reduced by other m eans, with the earlier development of all of the vascular phenomena be ing the most important difference.