Based on a structure function relationship, bone density distribution has been described as being representative of skeletal loading. As such, computed tomography (CT) may be used to visualize the structure of femoral head subchondral bone to allow in vivo quantification of joint mechanics without the need for implanted hardware. This study aims to characterize the distribution of subchondral bone density in the femoral head. We hypothesize that a non-uniform distribution of bone density will be observed, with correlation between left and right sides for a given patient. Femoral head surfaces were created bilaterally for thirty patients through semi-automatic segmentation of reconstructed CT data and used to map bone density, by shrinking them into the subchondral bone and averaging the grey values (linearly related to bone density) within five millimeters of the articular surface. Density maps were then oriented with the center of the head at the origin, the femoral mechanical axis (FMA) aligned with the vertical, and the posterior condylar axis (PCA) aligned with the horizontal. Twelve regions were created by dividing the density maps into three concentric rings at increments of thirty degrees from the horizontal, then splitting into four quadrants along the anterior-posterior and medial-lateral axes. Average bone density within each region was then calculated using histogram analysis. All analysis was performed with AmriaDEV 5.2.2 image analysis software (Visage Imaging, Carlsbad USA).Purpose
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