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 fixators, were evaluated by means of microangiography. Bilateral transverse mid-shaft osteotomies were performed in the tibiae of 16 dogs. The osteotomies 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, two, four and eight weeks post-operatively. After heparinization and euthanasia both femoral arteries were perfused with micronized barium sulphate, and microangiograms were performed in decalcified mid-tibial sagittal slices. Initial intramedullary revascularization as well as gap supply were already observed in some one-week microangiograms, and they were well developed in all of the two-week microangiograms. A network of parallel extraosseous blood vessels, orientated perpendicularly to 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 microangiograms most of the osteotomies showed only some traces of the above-mentioned vascular reaction. It can be concluded that the microangiographic pattern developed in external fixated osteotomies shows many similarities with those described in experimental fractures, reduced by other means, with the earlier development of all of the vascular phenomena being the most important difference.