The Journal of Bone and Joint Surgery, Vol 76, Issue 5 722-738, Copyright © 1994 by Journal of Bone and Joint Surgery, Inc
Long-term changes in the haversian systems following high-dose irradiation. An ultrastructural and quantitative histomorphological study
S Takahashi, M Sugimoto, Y Kotoura, K Sasai, M Oka and T Yamamuro
Department of Orthopaedic Surgery, Faculty of Medicine, Kyoto University, Japan.
The effects of high-dose irradiation on the morphology of haversian bone
were studied, over a fifty-two-week period, in seventy-seven adult rabbits,
after the administration of a single dose of radiation (therapeutic x-ray;
twenty-five, fifty, or 100 gray) to one knee joint. The specimens of bone
were examined with microangiography, light and transmission electron
microscopy, and histomorphometry. Analysis was performed on the haversian
bone in the subchondral bone plate of weight-bearing portions of the
femoral condyles. Microangiography demonstrated dilatation of the
microvasculature four weeks after irradiation. Beginning at twelve weeks,
there was a marked decrease in vascularity; no obvious recovery of the
subchondral bone had occurred by fifty-two weeks. At four weeks,
morphological analysis revealed two changes in the haversian canals: simple
occlusion of the haversian vessels with loss of cells in the canal, and
dilatation of the capillaries with abnormal resorption of the perivascular
bone matrix by osteoclasts. The abnormal bone resorption was not coupled
with subsequent new-bone formation, resulting in increased porosity.
Beginning at four weeks, a progressive decrease in the number of haversian
vessels and in cellularity became prominent. The decrease in cellularity
involved all types of cells, including endothelial cells, pericytes,
perivascular mesenchymal cells, osteoblasts, osteocytes, and osteoclasts.
The loss of perivascular cells was often but not always associated with
occlusion of the haversian vessels. Histomorphometry revealed both
time-dependent and dose-dependent decreases in capillary density (the
number of intraosseous capillaries per unit area) and in the number of
osteocytes in the subchondral bone plate. The porosity of the same areas
showed a significant increase by four weeks (p < 0.001 after
administration of twenty-five gray and p < 0.01 after administration of
both fifty and 100 gray), but between twelve and fifty-two weeks, there was
only a slight additional increase. Statistical analysis revealed
significant correlations between capillary density and osteocyte survival
(p < 0.001) and between capillary density and porosity (p < 0.001).
The portion of the subchondral bone plate that was located farthest from
the non-irradiated normal bone showed progressive damage and no sign of
recovery at fifty-two weeks.
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