Development of an Advanced External Fixation Device for Rat Femur Defect

The Regeneration of bone defect is a major challenge in modern tissue engineering and regenerative medicine and its appropriate animal model is needed to translate research finding into clinical application. Animal long bone defect model requires a special bone fixation device which has verified mechanical stability and reproducibility. This study was more focused on developing a stable external fixator when working with bone defect model in rats. Further studies using larger animal experimental groups are necessary to explore reproducibility. The external fixation devices were composed of one aluminum block and four pins. The pins were made of various types (material: titanium, stainless steel; thickness: 1.2, 1.3, 1.4 mm; pitch: 0.5, 0.3 mm). For the evaluation of mechanical stability difference due to various types of the pins, we did two sets of mechanical measurements (mean axial stiffness) of the external fixators using blocks and excised rat femurs, and in vivo performance over a 6-week period. Under 8 mm offset, 1.2 mm thickness titanium pins were appropriate for rat femur defect model when pitch decreased from 0.5 mm to 0.3 mm. In addition, we can observe the pitch of the pin have a decisive effect on mechanical stability of the external fixator and expect this finding to be contributive to the related future research.1111sciescopuskc