Pre-drilling and self-drilling pins screw-bone fixation stress interaction analysis induced by uniaxial compression loading

A newly designed Uniaxial external fixator which functions as a universal fixator in the application of all types of bone fractures is recently introduced by both Hospital Universiti Kebangsaan Malaysia (HUKM) and Universiti Malaysia Perlis (UniMAP). The Investigation is focused on identifying and measuring the performance in terms of strength or weakness of the fixator that is needed before the application to the human body. Hence, this research was conducted to determine the performance of Uniaxial external fixator which was based on geometry using different screw drilling techniques applied during an angled uniaxial compression load. A three-dimensional fixator-bone was constructed using different screw inserting techniques which was then converted into ANSYS v14.5 for the purposes of conducting a finite element analysis (FEA). Axial compressive loading with various degrees from 60 to 6300 N were applied to bone models to stimulate patient's daily activities while 10 to 100 N were applied to fixator models for the purposes of reviewing environmental loading to fixator-bone models. Findings revealed that maximum magnitude which caused deformation for predrilling and self-drilling models were located at the highest pin-bone interaction. Conversely, the maximum magnitude of the von Mises strain and stress was located at the lowest pin-bone interaction by omitting the existence of fixator for both Case 1 and 2. There was no obvious difference in the comparison of both models in terms of deformation. However, predrilling models have higher strain and stress than self-drilling models. In sum, findings indicated that self-drilling models have better performance compared to the predrilling models.