A microradiographic investigation of cancellous bone healing after irradiation and hyperbaric oxygenation: a rabbit study.

PURPOSE: To analyze the effect of irradiation on cancellous bone healing at different times after irradiation and to study if hyperbaric oxygen therapy (HBO) would affect the bone healing capacity, when delivered directly after irradiation. METHODS AND MATERIALS: Rabbits were given a single dose of 15 Gy (60)Co radiation to one hind leg, the other hind leg serving as control. A standardized defect through the femoral metaphysis of the rabbits was created by a trephine drill biopsy at different times after irradiation. New bone formation in the defect was evaluated by a new biopsy through the previous defect after a healing time of 8 weeks. The mineral contents of the biopsies were analyzed by microradiography and microdensitometry. RESULTS: There was a large variation in the bone-forming capacity expressed as bone mineral content between the animals. No statistically significant differences could be detected regarding the effect of irradiation, HBO, or delayed surgery. Qualitative histology revealed more pronounced inflammation, fibrosis, and bone resorption in the irradiated bone. CONCLUSIONS: No definite conclusions can be drawn from the results of this study, however it might be hypothesized that cancellous bone recovers faster than cortical bone from radiation trauma.

A histomorphometric study of bone reactions to titanium implants in irradiated bone and the effect of hyperbaric oxygen treatment.

The present study was undertaken to histomorphometrically analyze early peri-implant bone tissue reactions that occur after radiotherapy and to determine whether hyperbaric oxygen therapy (HBO) affects bone tissue at the microscopic level by altering bone morphology. Twelve rabbits received a single dose (15 Gy) of cobalt60 radiation to one hind leg and the other hind leg served as a control. Titanium screws were placed into the femur and tibia directly after irradiation. Six animals received HBO during the first 4 postoperative weeks. After 8 weeks of follow-up, bone specimens containing the screws were prepared for histomorphometry. Bone-metal contact and the amount of bone in the thread areas and in the mirror areas were measured in a blinded manner. Periosteal bone formation and bone remodeling decreased after irradiation; also after HBO treatment. Hyperbaric oxygen therapy improved bone formation in nonirradiated bone and to some extent also in the irradiated bone. Bone maturation was improved in the HBO animals after irradiation. It was concluded that irradiation reduces the capacity for osseointegration of titanium implants. Hyperbaric oxygen treatment may improve bone formation and especially has positive effects on bone maturation after irradiation.