Does low-dose X-irradiation promote mineralization of fracture callus in a rat model?

Abstract

We read the study “Low-dose X-irradiation promotes mineralization of fracture callus in a rat model” by Zhou et al. [1] published early this year in the journal, with great interest. In the “Introduction”, the authors stated that low-dose irradiation (LDI) showed beneWts as “accelerating wound healing” where Schindl et al. [2] were cited. However, in the study mentioned, “low-intensity laser irradiation with a single helium–neon (He–Ne, 632.8 nm)” was used. It should be noted that these two modalities (ionizing irradiation and laser irradiation) are very diVerent from each other radiobiologically. The methods seem to have some controversy that may alter the results, thus the conclusions. The authors stated that the rats were irradiated with a dose of 1 Gy using a 31 £ 23 cm Weld. This size corresponds to an area even more than a whole body irradiation Weld for a SpragueDawley rat. Whole body irradiation should be avoided in experiments investigating local eVects, and when previous studies were considered the authors used local irradiation like 3-cm diameter Welds [3]. In addition, irradiation should be applied under anesthesia to prevent excessive movements of the subjects. We believe that “Materials and methods” section is one of the most important parts of an experimental study and should be standardized to avoid subject, time and resource consuming where “reproducibility” can be provided. As the last but not the least, results should also be interpreted more carefully and our tendency to draw enthusiastic conclusions should be repressed. In the study, Wnal Wndings at week 4 showed no statistically signiWcant diVerences between the groups to reach a conclusion of “low dose irradiation promoting mineralization of fracture callus”. Most of the results that drive the authors to conclude were obtained from week 3 observations (Table 1). We should note that all mechanical properties were found as lower for LDI group than SHAM group at week 2. Even stiVness and energy showed lower results for LDI group, although they were not statistically signiWcant. The Wnal observation at week 4 should help us to draw more conclusions, where no statistically signiWcant diVerences between the groups could be detected in any of the results. In conclusion, “beneWcial” eVects of X-irradiation with 1 Gy should better be regarded cautiously and there is a greater likelihood of “no eVect” than “beneWcial” eVects.