Abstract
The stress and deformation characteristics of the proximal femur are very complex due to its intricate geometry that allows the femur to accommodate wide range of loading configurations. In laboratory bench testing, the complex physiological loading scheme is simplified so that the cause and effect of loading on the femur can be determined effectively. In this study, five human cadaveric femora were used to determine the regional deformation characteristics of the proximal half of the femur at adduction angles of neutral, 10, 20 and 30 degrees. The entire femur was cleaned of all soft tissues and fixed in to a steel cylinder using eight fixation pins and then potted with dental stone up to the mid-diaphysis level. Small reflective markers were then placed on the anterior and medial surface of the femur for the characterization of regional deformation. The cylinder is bolted on to a custom jig that is mounted onto the Instron machine and cyclic compressive loads ranging from 250 N to 2750 N were applied for ten cycles. The load application on the femoral head was via an X-Y translator so that the femur was being loaded in an unconstrained manner in the proximal region. The regional deformation characteristics were determined using a motion analysis system which provides non-contact measurement of the displacement of multiple reflective markers at 60 Hz. The results show that at neutral adduction angle, the greatest deformation was observed at the femoral neck region. With increasing adduction angle of the femur, the maximum deformation region shifts to the diaphyseal region. The quantitation of the regional deformation of the femur under various loading schemes is necessary in order to effectively evaluate the structural integrity of the femur and hip systems.