[Incorporation of cortical intercalary bone allografts. Experimental study on rabbits]

An experimental study was carried out on 40 rabbits in order to evaluate the incorporation of large intercalary bone allografts and the influence of freezing on the bone graft. In 36 rabbits resection of 3 centimetres of diaphysis of the tibia was carried out and the defect was rebuilt with different types of bone graft: fresh autograft and frozen autograft, fresh allograft and frozen allograft; osteosynthesis was carried out with two intramedullary Kirschner needles. Monthly radiological studies were made until the sacrifice of the animals, at 2, 4 and 8 months. A densitometric, histological and diaphanisation study of the tibias was made with Spalteholz's technique. In 24 animals 25 mg/kg of oxytetracicline was administered 3 and 6 days before sacrifice, to study the velocity of bone apposition in the graft. We observed a good and excellent radiological consolidation in 80% of the grafts (99% in the autografts and 66% in the allografts). The bone density showed a fall until the 4th month due to bone reabsorption except in the group of fresh allografts. The revascularization of the allografts was slower and poorer than the autografts, but with the same vascular pattern. Bone incorporation and neoformation were greater in the autografts without significant differences with the frozen allografts. The speed of bone apposition did not change with the different types of bone graft used. Freezing facilitated and accelerated incorporation and the quantity of bone neoformation of the allografts.