Dynamics of irradiation injury to bone tissue. A vital microscopic investigation.

The dynamic changes after a single dose of 15, 25 or 40 Gy 60Co were followed in a titanium vital microscopic bone chamber which permitted observation of the same tissue compartment for over 2 years. The chamber consists of a hollow screw containing 2 glass rods 100 micron apart. The device was inserted into the cortex of the proximal tibial metaphysis of a rabbit. During a healing period of 4 to 6 weeks the space between the glass rods became filled with bone and vessels and in some cases fat. Once a steady state in bone remodelling had been achieved, the animals were irradiated. Vital microscopy was then performed at regular intervals. Mature bone was relatively radioresistant since remodelling continued at a normal rate. In contrast, immature woven bone remained unlamellarized and in some animals tended to increase in amount. The vascular architecture was largely unaltered, even after 40 Gy. Thrombosis or hemorrhage clearly attributable to irradiation was not noted. Initially, the number of fat cells was reduced but repopulation was later seen in several cases.