The vascularity of atrophic non-unions
Introduction
Atrophic non-unions are usually encountered after high energy and open injuries. They are thought to occur as a result of impaired local blood supply [1], [2]. This suggestion is supported by experimental studies which have shown that interrupting the blood supply to a fracture impedes normal bone healing [3], [4]. It is therefore surprising that studies of human atrophic non-unions have shown that the gap tissues can be well vascularised [5], [6], [7].
We wished to investigate this apparent discrepancy using an experimental model of atrophic non-union and test the null hypothesis that there is no difference between the vascularity of the gap tissues of established atrophic non-unions and normally healing osteotomies. The aim of the study was to examine the concentration of the vessels within the osteotomy gap and the serum concentration of endothelial cell stimulating angiogenesis factor (ESAF) which is known to be an important angiogenic factor involved in bone healing [8] and which has been explored as a potentially useful marker for impaired human tibial fracture healing.
Section snippets
The atrophic non-union model
We used a previously described rabbit model of atrophic non-union [9] which involves creating a unilateral mid-diaphyseal tibial osteotomy and removing the periosteum and endosteum both proximal and distal to the osteotomy for a distance equivalent to one diameter of the tibia. The osteotomy was stabilised with a unilateral fixator, which was applied to the medial aspect of the tibia and finally a 2 mm gap was introduced at the osteotomy site by acute distraction. Weight bearing was never
Results
The operations were well tolerated with no incidences of premature death, infection, or fracture. However, in one case the external fixator failed leading to the collapse of the osteotomy gap; this animal (16 week experimental group) was excluded from the study.
The radiographs that had been obtained 8 and 16 weeks after the operation demonstrated that all the animals within the control group had united and all the animals within the experimental groups had formed non-unions. There was no
Discussion
This study has shown that at 8 and 16 weeks after the operation the interfragmentary gaps of atrophic non-unions are vascularised. Therefore, the null hypothesis that there is no difference between the vascularity of the gap tissues of established atrophic non-unions and normally healing osteotomies has not been rejected.
However, at 1 week after the operation, there were no vessels within the interfragmentary gap of those osteotomies which would later develop into atrophic non-unions in
Acknowledgements
We are very grateful to Dr Barry Mclaughlin from the Department of Clinical Dermatology at Manchester University who kindly performed the ESAF assays. We gratefully acknowledge the grants from the Wishbone Trust and the Oxfordshire Health Services Research Committee.
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