Reconstructive surgery has reached a point where now massive bones with or without articular cartilage can be replaced in such cases as resections for tumors, chronic infections, hydatid cysts, traumatic arthritis and intractable juxta-articular non-union. The histological fate of autogenous and allogenous bone grafts has been described in numerous papers since 1901. However, few workers have reported on transplantation of bone as an organ, the bone being composed of articular cartilage, cancellous bone, cortical bone, marrow, and fat. It is well known that tissue-incompatible allogenous marrow has strong antigenicity that renders transplantation immunity to the host.
In order to observe histological and rentgenographic changes of autogenous and allogenous bone transplantation, the distal portions of the left femurs of one hundred rabbits were resected at a point one centimeter above the epiphyseal plate. In fifty of these rabbits, the resected femur was freed of any soft tissue attachment and was replaced in situ as a fresh orthotopical autogenous transplantation. In the other
fifty, the femurs of pairs of rabbits were exchanged as fresh orthotopical allogenous transplantations. In a control group of twenty rabbits, the left distal femur was fractured surgically without disturbing its blood supply and soft tissue attachment. All the rabbits were then sacrificed from three days up . to twelve weeks postoperatively.
1. In the autogenous group, new bone regeneration was observed as early as the third day. Lamellar structure was evident from the second week. Bony union between the host and grafted bone took place from the sixth week with remodelling of new trabeculae and was almost completed by the twelfth week. with creeping substitution of the grafted bone still under way.
2. In the allogenous group, new bone formation was seen on the cortical surface from the third day, but gradually decreased from the third week. Immature fibrous callus was transformed into bony callus by metaplasia of surrounding young fibrous tissue, which was rich on the host side and progressed distally. Osteogensis within the grafted bone was scanty and bony incorporation was incomplete at the twelfth week even though creeping substitution was still in progress.
3. Infiltration of inflammatory cells was much more conspicuous in the allogenous group than in the autogenous group. Revascularization, absorption of organized hematoma, bony substitution, and remodelling of newly formed bone were all delayed in the allogenous group. Marrow regeneration, seen from the eighth week in the autogenous group, was delayed in the allogenous transplantation, being increasingly so in the more distal part of the grafted bone.
There is evidence that new bone formation, creeping substitution and revascularization are all delayed in allogeneous bone transplantation. As suggested by many, transplantation immunity following tissue incompatibility and vascular interruption by surgery may be responsible for the delay. It is believed that rigid fixation of the host and grafted bone and a sufficient period of immobilization are mandatory in order to ensure bony incorporation in allogenous transplantation.
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