The Journal of Bone and Joint Surgery, Vol 70, Issue 3 392-399, Copyright © 1988 by Journal of Bone and Joint Surgery, Inc
Effects of irradiation on cortical bone and their time-related changes. A biomechanical and histomorphological study
M Maeda, MH Bryant, M Yamagata, G Li, JD Earle and EY Chao
Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905.
The effects of high-dose irradiation on the biomechanical and morphological
properties of cortical bone and their time-related changes were studied in
male Sprague-Dawley rats. A single fraction of 3500 rads was applied to the
middle part of the right thigh. Age and sex-matched control rats that did
not receive radiation were used for comparison. Two weeks after
irradiation, the animals had lost weight and disappearance of bone cells,
shrunken osteocytes, and significantly decreased bone-turnover activities
were noted. The bone marrow showed reduced hematopoietic elements and
sinusoids with increased fat. No change in the torsional strength and
geometric properties of bone was noted at this time. Six to ten weeks after
irradiation, histopathological abnormalities of the bone persisted, and
there was an accelerated resorption process. However, significant increases
in the strength and cortical area of bone appeared only in the
non-irradiated, contralateral femur. On the irradiated side, decreased
cortical area and increased porosity of bone were found at fourteen to
eighteen weeks when compared with the control rats. Other
histomorphological properties, such as bone porosity, osteocyte count, and
periosteal new-bone formation, appeared to recover eighteen weeks after
irradiation, as they became similar to the values for the age-matched
normal control rats.