LAUSR

Objectives Evaluate the effects of ionizing radiation on microarchitecture, the osteocyte lacunar network, and collagen maturity in a bone repair site. Materials and methods Bone defects were created on tibias of 20 New Zealand rabbits. After 2 weeks, the animals were randomly divided into ( n  = 10) NoIr (nonirradiated group) and Ir (irradiated group). In the Ir, the animals received single-dose irradiation of 30 Gy on the tibia and were euthanized after 2 weeks. Bone microarchitecture parameters were analyzed by using micro-CT, and the osteocyte lacunar network, bone matrix, and collagen maturation by histomorphometric analysis. The data were analyzed using unpaired Student’s t test ( α  = 0.05). Results Trabecular thickness in Ir was lower than that in NoIr ( P  = 0.028). No difference was found for bone volume fraction and bone area. Lacunae filled with osteocytes were more numerous ( P  < 0.0001) in NoIr (2.6 ± 0.6) than in Ir (1.97 ± 0.53). Empty lacunae were more prevalent ( P  < 0.003) in Ir (0.14 ± 0.10) than in NoIr (0.1 ± 0.1). The mean osteocyte lacunae size was higher ( P  < 0.01) in Ir (15.4 ± 4.41) than in NoIr (12.7 ± 3.7). Picrosirius red analysis showed more ( P  < 0.05) mature collagen in NoIr (29.0 ± 5.3) than in Ir (23.4 ± 4.5). Immature collagen quantification revealed no difference between groups. Conclusions Ionizing radiation compromised bone formation and an impairment in bone repair in irradiated woven bone was observed. Clinical relevance Before radiotherapy, patients usually need surgical intervention, which may be better performed, if clinicians understand the repair process in irradiated bone, using novel approaches for treating these individuals.