Provoked repetitive healing of mature bone tissue following irradiation. A quantitative investigation.

A titanium implant, the bone harvest chamber (BHC), was used to investigate the regenerative capacity of mature bone after irradiation. One BHC was inserted in each proximal tibial metaphysis of a rabbit. One of these implant sites was irradiated (60Co single dose) to either 15 or 25 Gy while the other served as control. Newly formed bone grew through a canal that penetrated the implant. This newly formed bone was harvested from the implant every three weeks following irradiation and then quantified by microradiography and computer-assisted densitometry. In this way a ratio between bone formed on the irradiated side in comparison with the control could be established. An immediate depression in bone formation compared with the non-irradiated controls, was seen at both dose levels. A recovery in bone regenerative capacity was seen at 15 weeks after 15 Gy while the decrease in bone formation remained constant after 25 Gy during the 30 week follow-up period.