The use of circular external fixator in the reconstruction of experimental tibia segmental defects in dogs

59 8. SUMMARY In this study, bone transport technique using circular external fixator were repaired experimentally induced tibial defects in dogs. The results were evaluated on the basis clinic, radiographic, and histopathologic. Eighteen crossbred dogs of different races, ages and sexes were used. Circular external fixator was construcred with four rings and three connecting rods. Each ring was fixed to the tibia with two 1.5 mm kirchner wires with an angle of 60 ° to 90 ° between them.. About 20 mm long bone segment was removed from the middiaphysis of the tibia. Corticotomy was performed on the cranial aspect of the proximal tibia, preserving the periosteum. After a six days latency period, bone transport was performed at a rate 0.5 mm every 12 hours for 20 days. Following the completion of the transport, procedures like compression-distraction, consolidation and dinamisation were performed for 7, 40 and 17 days, respectively. The fixators were well tolerated by these cases. Pin track infections were the most common complications. The cases is allowed up in the second postoperatif weeks partial weight bearing then fourth weeks full weight bearing. The muscles of the left extremity showed sings of atrophy as compared with the right extremity until removal of the fixator. These sings of atrophy were very slight at three monts after operation. Edema were observed first two weeks. Any cases were seen fixator deformation and wire breakage. Pin loosening was observed in five cases. Collogen fibers in the distraction area was seen 2 * weeks after distraction and new bone are organized in the direction of the distraction. Mineralization of collogen fibers started at the proximal and distal bone ends. Bone development in the distraction area and distal bone union was seen normally in all cases. It was observed in three cases incomplete corticotomy, in three cases deviation, and refracture in two cases in the distal bone region Bone transport technique used circular external fixator can be satisfactorily used for the recontraction of large tibial defects in dogs.