Determination of Hip Joint Contact Pressure from CT or MR Images

The peak hip contact stress measured experimentally is usually higher than the peak contact hip stress estimated from mathematical models, presumably due to negligence of local variations in the mechanical properties of the cartilage in mathematical models. In this study, a mathematical model which was previously verified in clinical studies, has been adapted to describe the influence of the specific local geometry of the hip on the contact stress distribution. CT data from Visible Human Project have used to create a three-dimensional model of the hip joint and simulated antero-posterior radiogram. It is shown that including more accurate geometry from the CT images considerably increases peak contact stress in comparison with the simplified model based on radiogram analysis. However, the local variations in joint surface geometry estimated from CT do not considerably affect the overall stress distribution. It follows that although the simple mathematical model used in the clinical studies cannot predict local-peaks of hip contact stress if the cartilage properties are not known, it provides an estimation of the contact stress distribution pattern that proves to be significant in the long-term prediction of the development of the hip.