Fresh Tubular Long Bone Autografts and Allografts in the Healing of Canine Ulnar Defect Fixed with Intramedullary Kirschner Wire

Abstract

We developed a model where a 2-cm full-thickness canine ulnar defect bridged with a tubular diaphyseal bone transplant was stabilized with an intramedullary Kirschner wire. This model was used to compare tubular autografts and allografts in the reconstruction of segmental ulnar defects in 12 adult beagle dogs. The dogs were followed for nine months and X-ray radiographs were taken every three weeks. The overall healing was good and all the dogs were able to walk normally during the follow-up. After nine months, the ulnas were harvested and mechanical testing and histological analyses were made. Of the ulnar defects, 4/6 in the autograft group and 3/6 in the allograft group had a complete union. Of the Kirschner wires, 6/12 had broken during the follow-up. This did not have any effect on the bone union, however. The autograft group had better results in mechanical testing although the difference was statistically significant only for maximal absorbed energy. We conclude that the segmental ulnar defect model fixed with an intramedullary wire seems to be a feasible alternative in bone transplant studies, although the semirigid fixation resulted in breakage of the wire in many cases. The overall healing was good after both autograft and allograft transplantations, but autografts seemed to be slightly better.