ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

5. RESULTS
The orthotropic elastic moduli were found to lie between 0.38GPa and 5.42GPa. The
mean orthotropic elastic modulus was 2.24GPa, with a standard deviation of 1.22GPa.
The mean value of the largest direct stiffness was found to be 4.79GPa, with a standard
deviation of 2.12GPa. The relation between the stiffness and the ratio BV/TV was
analysed. It was found to correlate well, with a correlation coefficient of 0.92. The mean
porosity of the OP samples was 13.5% lower than that of the OA. The mean error in
assuming orthotropy according to van Rietbergen [26] was (32 ± 11) %. The variation
of porosity, mean Young’s modulus and mean error in orthotropic assumption with
location in the femoral head are shown in Figures 2, 3 and 4.
Figure 2: Porosity variation with locations in the femoral head, where A is anterior, C is
central, P is posterior, S is superior and I is inferior regions. Plotted values have also been
colour coded for clarity – blue is lowest and red is highest.
Figure 3: Mean Young’s modulus variation with locations in the femoral head, where A is
anterior, C is central, P is posterior, S is superior and I is inferior regions. Plotted values have
also been colour coded for clarity – blue is lowest and red is highest.