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The classification and treatment of pathologic peri-acetabular lesions was initially described by Harrington5. However, the ability to predict impending pathologic fractures is difficult. Proposed treatment in the literature has included external beam radiation and cemented total hip arthroplasty. Based on a cadaveric biomechanical model, our goal is to delineate the risk of pathologic fracture in contained Harrington class 1 lesions.
Eight paired hemi-pelvises were utilized to create peri-acetabular defects with its paired side to serve as a control. Volumetric measurements were taken via computed tomography then converted to a percentage of the peri-acetabular volume. Each paired specimen was axially loaded to catastrophic failure via Material Testing System (MTS, Minneapolis, MN).
The results demonstrate that larger (>40%) contained peri-acetabular defects can support significant less load than an intact acetabulum. Smaller defects did not fail at significantly less load, and their location of failure was not consistent. Though the load to failure was significantly less than the intact controls, the levels were found to be nearly 2.5 times the normal physiologic loads that the hip encounters at its peak3. These results do indicate that volumetric measurements via CT scan is a simple technique, and its clinical relevance as a tool to predict pathologic fracture of peri-acetabular lesions must be further investigated.
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