[Fate of massive retrieved human bone allografts]

To study retrieved massive human allograft specimen after they had been in situ for four to sixty-five months, and to investigate the changes union, bone replacement and degradation of articular cartilage.

BMP gene expression in the specimen was also studied with in situ hybridization, immunohistochemical methods, and the observations were correlated with the clinical and isotope scan date.

The union between the allograft and the host was achieved by the formation of an external callus derived from the cortex of the host. New bone replacement took place slowly. Analysis of the articular cartilage revealed evidence that some chondrocytes had survived in non bearing area of the articular. The expression of BMP in the surface of the cortex and united callus was positive 4 months after implantation. But it was negative in the center of cortex after it had been implanted for over 12 months. An external callus formed from the cortex of the host. Some chondrocytes survived in non-bearing area of the articular. Neovasculature penetrated into osteoarticular.

Bone absorption may be the cause of collapse of articular surface. The results suggest that large allografts in humans are osteo-conductive rather than inductive. Incomplete repair of osteon may be related to slowed replacement of massive human allograft.