Strain measurement near the external fixation pin insertion site in an ankle joint fracture model using the digital image correlation method

Abstract

This study aimed to construct an external fixation model using a cruciate technique that simulates muscle tension under resting and loading conditions during rehabilitation. This model serves as a foundational approach for evaluating the mechanical stability of human ankle joints through strain analysis. Additionally, the feasibility of visualizing strain near the fixation pin insertion site in the cruciate technique model was examined using stereo-DIC, with the goal of identifying mechanical indices for external fixation stability from an experimental mechanical perspective. External fixation often involves inserting the fixation pin obliquely into the bone surface, complicating the adjustment of the camera for accurate imaging. To address this challenge, we experimentally determined a measurement range that minimizes dependence on the stereo-DIC imaging direction. The results demonstrated successful visualization of the principal strain distribution near the fixation pin insertion site in the cruciate technique model using stereo-DIC. However, the maximum principal strain value was found to be influenced by the imaging direction.