Pelvic fracture is considered a common and sometimes fatal injury. There are still developments in novel pelvic fixations. In order to investigate the performance of these fixations, a specialized testing set-up is required. Typically, the strains of a few selected points and the changes in the boundary condition on a pelvis are evaluated. The goal of the current study was to investigate the strain field on a region of interest of a broken hemi-pelvis as well as the interfragmentary movement in 3D. Both goals have not been achieved in other studies yet.

A multi-axis biomechanical testing apparatus (MABTA) was previously developed in the Department of Mechanical Engineering of the University of Alberta. The current study investigates modifications incorporated into the MABTA such as the force direction exerted by the prosthetic femur. Novel criteria for determining the loading direction is presented. Also the errors associated with the apparatus were evaluated where the error of the motor and load cell were determined.

In order to investigate the strain field in a selected region of interest, the MABTA was equipped with a 3D digital image correlation (DIC) system. The error of pure movement using the DIC system was determined at 3.5%, and the error of measuring the strain field was less than 6%. The novel aspect of the work is to use DIC for measuring the gap opening in three directions. It allows investigating the value and mode of opening anywhere in the region of interest. In order to measure the gap opening, two Matlab programs were developed and tested to have the accuracy of 5 µm for in-plane opening and 30 µm for out-of-plane opening. Finally, two tests on an intact and a broken hemi-pelvis were done, and the results of the strain field and the inter-fragmentary movement were obtained.