Cortical Bone Modifications after Radiotherapy: Cortex Porosity and Osteonal Changes Evaluated Over Time

Abstract

Aiming to evaluate cortical bone microarchitecture and osteonal morphology after irradiation, twelve male New Zealand rabbits were used. The animals were divided: control group (no radiation-NIr); and 3 irradiated groups, sacrificed after: 7 (Ir7d); 14 (Ir14d) and 21 (Ir21d) days. A single radiation dose of 30 Gy was used. Computed microtomography analyzed the cortical microarchitecture: cortical thickness (CtTh), bone volume (BV), total porosity (Ct.Po), intracortical porosity (CtPo-cl), channel/pore number (Po.N), fractal dimension (FD) and degree of anisotropy (Ct.DA). After scan, osteonal morphology was histologically assessed by means: area and perimeter of the osteons (O.Ar; O.p) and of the Haversian canals (C.Ar; C.p). Microtomographic analysis were performed by ANOVA, followed by Tukey and Dunnet tests. Osteon morphology analyses were performed by Kruskal-Wallis, and test Dunn’s. Cortical thickness was significant difference (p<0.010) between the NIr and irradiated groups, with thicker cortex at Ir7d (1.15±0.09). The intracortical porosity revealed significant difference (p<0.001) between irradiated groups and NIr, with lower value for Ir7d (0.29±0.09). Bone volume was lower in Ir14d compared to control. Area and perimeter of the osteons were statistically different (p<0.0001) between NIr and Ir7d. Haversian canals also revealed lower values (p<0.0001) in Ir7d (80.57±9.3; 31.63±6.5) compared to NIr and irradiated groups. Cortical microarchitecture was affected by radiation, and the effects appear to be time-dependent, mostly regarding the osteons morphology at the initial days. Cortex structure in Ir21d revealed similarities to control suggesting that microarchitecture resembles normal condition after a period.

Microstructural changes in the irradiated and osteoradionecrotic bone: a SEM study

“…The heterogeneity of the osteon morphology following irradiation has been reported in an animal study. 22 The difference in the osteon sizes and morphology was evident in our study groups. The lamellar organization around the HCs was evident in our control and many irradiated samples both under LM and SEM.…”

Direct Assessment of Rabbit Cortical Bone Basic Multicellular Unit Longitudinal Erosion Rate: A 4D Synchrotron-Based Approach

“…( 68 ) Interestingly, timed analysis of rabbit tibias (7, 14, 21 days) post‐exposure to a single dose of 30 Gy showed that the majority of impacted cortical parameters, including porosity, recovered to non‐irradiated levels 14 and 21 days post‐exposure, suggestive of a potential correlation between bone turnover recovery and time post‐exposure. ( 69 ) Although the rabbits in our study had the added variable of PTH treatment, their cortices were subjected to non‐therapeutic radiation doses and assessed after a shorter period (14 days) post in vivo imaging, which may explain why we found little evidence of significant radiation dose effects. Notably, in this study, we only reported the incident dose; however, since the synchrotron beam utilized here was monoenergetic, the absorbed dose in the bone tissue here is less than the case of polychromatic X‐ray beam from X‐ray tube sources.…”

Clinical dental management of the head and neck irradiated patient

“…This indication is based on the progressive process of connective tissue fibrosis that reduces the vascularization, cellularity and oxygenation of oral tissues, especially bone tissue, which can impair the repair processes 5,12,13,28 . The bone tissue has the slower regenerative potential than soft tissues 2,5,14,28 . During the healing phase, especially the post-extraction alveolar repair occurred by second intention, makes this tissue more susceptible to contamination and subsequent development of necrotic lesions, which are difficult to treat 2 .…”

“…Ionizing radiation produces hypoxia, hypocellularity and hypovascularization that can alter the regenerative potential of the soft and hard tissues 2,13,14 . Changes in tooth and bone structure can occur due to degradations in amine components that can mechanically alter enamel 15,16 , dentin 12 , and bones 14,15,17 .…”

“…Ionizing radiation produces hypoxia, hypocellularity and hypovascularization that can alter the regenerative potential of the soft and hard tissues 2,13,14 . Changes in tooth and bone structure can occur due to degradations in amine components that can mechanically alter enamel 15,16 , dentin 12 , and bones 14,15,17 . The effect of ionizating radiaton on the salivary flow and the xerostomia reduce the protection of this fluid against pathogens and enhance the friction on the mucosa during the oral chewing that could be the trigger for the occurrence of the mucositis lesions 18 .…”