3D Models of Fractured Pelvic Bones for Analysis of Symmetry and Deviation

Pelvic fractures are a fairly common result of falls, automobile collisions, or other direct impact incidents. Most fractures are relatively mild and not life-threatening, but severe damage may have debilitating effects on the victim's health and quality of life. Pelvic breakage often requires surgery to alleviate, but procedures may be difficult given the complex anatomical structure of the area and the specific location of the fractures. This project aimed to make the planning stage easier for surgeons by analyzing left-right symmetry of the pelvis and using this property to create, in cases where one side is fractured and the other remains intact, 3D models of reconstructed pelvic fractures. Pelvic bone has been proven to be highly symmetrical. This method would provide surgeons with a clearer idea of how to best reassemble and otherwise correct fractures in the pelvis. First, various one-sided pelvic fractures from a batch of anonymized subjects obtained from the University of Alberta Hospital were digitized in medical imaging software. Data from six subjects in total was used in the collection of results. The digitized pelvises were then used to construct 3D models. The fractured pieces were aligned in best-fit with a mirrored intact side. Colour deviation maps, which differentiated between areas of high and low symmetry by measuring the degree of point deviance against a scale, were then generated. Deviance was generally more prevalent along the fracture lines. The predefined threshold considered a maximum of 2 mm of deviation as highly symmetrical. The average RMS value was found to be 1.65 mm and the average percentage of points within 2 mm of difference was 85.1%, indicating that the pelvic bones studied possessed a reasonably high degree of left-right symmetry. The results from this study suggest that this virtual reconstruction method is reliable for use in surgical planning for one-sided pelvic fractures

Regional Symmetry of the Pelvis

Understanding the left-right symmetry of the pelvis can assist with the virtual reconstruction of fractured pelvises in the future. Further specifying the different regions can give more information regarding the anatomy of the bone. CT scans of intact pelvises are turned into 3D models using a computer program called Mimics. The femurs and spine are removed manually to isolate the bone. The model can then be analyzed and the regions defined. The pelvis is split into three pieces using the program Geomagic, the iliac, acetabular, and pubic rami regions. The two cuts are made based around the highest and lowest points of the acetabular cup. From here each cut piece can be mirrored and aligned with the opposing side of the pelvis. Colour deviation maps can then be generated to visualize the asymmetry, as well as the RMS value and the percentage of points within a 2 mm deviation threshold. The average RMS values are below 2 mm and the percentage of points within 2 mm is high. My research reflects that the pelvis is symmetrical and may be used to assist in the surgical planning process of pelvic fractures