Alterations in bone regenerative capacity after low level gamma irradiation. A quantitative study

In the present study the influence of single 2.5 and 5 Gy doses of irradiation on the regenerative capacity of mature bone tissue has been investigated. To the knowledge of the present authors, no quantitative analysis of bone repair after low doses of irradiation has been presented previously. The experimental model used was the Bone Growth Chamber (BGC), which is a porous implant made of titanium. Each one of twenty animals was irradiated with 2.5 or 5 Gy to one tibial metaphysis. Directly after irradiation each animal had BGC:s inserted bilaterally into the tibial metaphyses. Thus, each animal served as its own control. Four weeks after irradiation the BGC:s were removed and the newly formed bone was collected from the implant pores and was analyzed by microradiography and quantified by microdensitometry and histology. It was found that 2.5 Gy irradiation led to no statistically significant alteration in bone formation as compared to non-irradiated controls. At the 5 Gy dose level, however, there was a significant reduction of bone formation as compared to non-irradiated controls.