Lei Wang, Jin Shao, Tingjun Yea, Lianfu Deng, and Shijing Qiu
Screw implantation inevitably causes microdamage in surrounding bone. However, little is known about the detailed characteristics of microdamage in peri-screw bone. In this study, we developed a method to construct microdamage cast with methylmethacrylate (MMA) and observed the cast using scanning electron microscopy (SEM). In basic fuchsin stained bone sections observed by bright-field and fluorescence microscopy, diffuse damage, cross-hatched damage, and linear cracks were all presented in peri-screw bone. Using MMA casting/SEM method, we found numerous densely packed microcracks in the areas with diffuse damage. The osteocyte canaliculi and the microcracks consisting of diffuse damage had a similar diameter (or width), usually <0.5 μm, but their morphology was largely different. In the area with cross-hatched damage, the orientation of microcracks was similar to that in diffuse damage, but the number was significantly decreased. Many microcracks were thicker than 1 μm and associated with a rough surface. Large linear cracks (∼10 μm in diameter) occurred in different areas. Plenty of microcracks were present on the surface of some linear cracks. In conclusion, the MMA casting/SEM method can demonstrate the three-dimensional morphology of different types of microdamage, particularly the microcracks in diffuse damage, which are unable to be shown by light microscopy.