Extracorporeal irradiation and incorporation of bone grafts. Autogeneic cortical grafts studied in rats

The incorporation of resected, extracorporeally irradiated (1, 5, 25 and 50 kGy) and orthotopically reimplanted autogeneic cortical bone was investigated in 116 adult Wistar rats. 7 mm-long diaphyseal segments of the tibia were resected, irradiated and reimplanted using K-wire osteosynthesis. Autogeneic fresh grafts served as controls. Graft healing was evaluated by radiography and histomorphometric study at 3, 6, 9, and 12 weeks. At 3 weeks, two thirds of the 50 kGy irradiated grafts were fractured and therefore the series with this dose was interrupted because of mechanical graft insufficiency. After 3 and 6 weeks there were no statistically significant differences among the control group and 1 or 5 kGy irradiated grafts. The healing of 25 kGy irradiated grafts was delayed from the sixth week onwards and continued until the end of the experiment at 12 weeks (50% reduction of incorporation). The incorporation of 1 and 5 kGy irradiated grafts showed a 16% (1 kGy) to 24% (5 kGy) delay at 12 weeks, compared to autogeneic fresh grafts. 1 and 5 kGy irradiated autogeneic bone grafts retain most of their biological potential. Resection, extracorporeal irradiation and reimplantation of bone tumors may therefore be a possible alternative to allografting.