Early Changes of the Growth Zone in Rabbit Following Roentgen Irradiation

Effects of irradiation on the biomechanics of osseointegration. An experimental in vivo study in rats

The present study reports on the late effects of increasing doses of radiation on the biomechanics of commercially pure titanium implants (fixtures) installed in the proximal tibia in 26 rats. Twelve weeks after various doses (10, 20, 30, and 35 Gy) of irradiation, the fixtures were inserted into rat tibiae, and after another eight weeks these were tested mechanically in vivo. Acute dose dependent skin reactions developed after all doses except 10 Gy, but most subsided within two to three weeks. There was a statistically significant reduction in torsion but the pull-out load was not significantly reduced for single doses up to 30 Gy. Histological analysis showed that bone remodelling was impaired. Shear stresses and shear moduli were estimated for the bone-implant interface and in the surrounding bone tissue. These estimated stresses and moduli were not found to be correlated to the dose of radiation.

Effects of pre- and postoperative irradiation on the healing of bone grafts in the rabbit

Healing of cellular bone grafts irradiated at various times in the postsurgical course was compared to the healing characteristics of bone grafts placed into already irradiated tissue and to controls of irradiated host mandible in a rabbit model. Physical graft consolidation was assessed by load stress characteristics and serial histologic examination. Results indicated that grafts placed into already irradiated tissues failed to form bone in both phases of expected regeneration resulting in structurally weakened and histologically deficient ossicles. Bone grafts irradiated after placement were tolerant of irradiation. Bone grafts irradiated after four weeks were found to be less affected by irradiation than those irradiated within the first four weeks, forming an ossicle structurally and histologically superior to that of bone ossicles developed from grafts placed into irradiated tissues.

Effects of 60CO-gamma-irradiation on the early ingrowth of an autogenous bone inlay into an artificial defect in the rabbit mandibula

The incorporation of an autogenous humeral bone inlay into a previously irradiated mandibula was studied in 23 adult rabbits. A single exposure of 1000, 2000 and 3000 rads was given 1 or 8 weeks before the grafting into an artificially created defect in the rabbit mandibula. The observation time was 30 days. The results were compared to those obtained in 6 non-irradiated rabbits operated in the same way and after the same observation period. The callus formation around the graft was reduced to less than half the amount measured with morphometry in rabbits irradiated greater than or equal to 2000 rads one week preoperatively as compared to that in the non-irradiated group. The periosteal callus formed by the host bone was reduced with increasing preoperative radiation doses and the longer interval between irradiation and bone grafting. Practically all callus was formed by the graft constituents (particularly the periosteum) after heavier preoperative radiation doses and the longer interval between irradiation and bone grafting. The new bone formation started some days later and was of an inferior quality with larger preoperative doses and the longer interval between irradiation and bone grafting.

Bone growth in the rabbit after irradiation

The effect on bone growth of two locally given, different, unfractionated radiation doses (0.1 and 24 Gy) was tested in a rabbit litter aged 57 days. The effects on growth were registered with roentgen stereophotogrammetric length measurements for 75 days after irradiation. Growth of the right irradiated tibia was compared with the growth of the left non-irradiated tibia. After 7 to 9 days, 24 Gy had caused a linear fall in growth to about 15 per cent. After a period of complete cessation, a slight growth was registered. 0.1 Gy had no significant growth retarding effect.