The pubic rami fracture is a common pelvic injury for vehicle occupants as well as for pedestrians struck during side impacts. While many studies have investigated the structural properties of the pelvis in lateral loading, relatively few investigations have compared the applied loads with local response of the pubic rami. The aims of this study are to investigate the force transmission paths and strain distribution for the anterior (i.e., rami) and posterior (i.e., sacrum) regions of the pelvis under acetabular impact loading. Eight male postmortem human surrogate pelves were tested to failure in quasi-static (n = 2) and dynamic (n = 6) conditions using an Instron test machine and a drop-tower, respectively. The denuded pelves were potted and then cut along a line connecting the greater sciatic notch and the middle of anterior iliac spine. Lateral loading was applied at the site of the acetabulum using a custom-fit femoral head surrogate made of steel. An acoustic emission (AE) sensor and uniaxial strain gages were affixed to the four rami (anterior and posterior) to assess the time of fracture as well as the regional strain distribution. In addition to measuring the impacting force, the loads transmitted through the pelvis were recorded on the non-struck side using load cells at the inferior and superior potting attachment points. To better understand the load path and strain distribution through the rami a finite element model of a human pelvis was developed from computer tomography data and validated based on available published test data. Then, the lateral impact test was numerically simulated and the model responses were mostly within the min-max ranges of the test data. The test data and FE simulations showed that prior to the fracture the pubic symphysis joint transmitted the higher percentage of load (about 66% in dynamic tests). The strain distribution analysis of the impact pelvic tests showed that the pubic rami are subjected predominantly to compressive stress on the anterior side and tensile stress on the posterior side. While the anterior pubic side of the non-impact part of the pelvis was always subjected to compressive stress, some test variability was observed on other regions of the non-impact sides. In addition to providing validation data for computational models, the results highlight the vulnerability of pubic rami structure in carrying lateral load in acetabular impacts and may lend insight into the development of injury countermeasures.

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