## 3 Results
### Hybrid Continuum Models  
The hybrid isotropic model reached a state of convergence after 24 iterations. The cortical thickness distribution is shown in Figure 4a-c. Shell elements were the thickest at the superior sacrum, along the arcuate line, around the sacroiliac joint, along the superior cubic ramus and in the region of the greater sciatic notch. Areas with thin shell elements were found on the superior ilium, inferior public ramus, ischial tuberosity, pubic tubercle and supraacetabular region. The [PERSON]'s modulus distribution of the continuum elements in the hybrid isotropic model are shown in Figure 5a-c. Regions with high stiffness were found along the arcuate line, anterior superior sacrum, superior pubis ramus, acetabulum and near the greater sciatic notch. Conversely, large parts of the ilium, inferior pubis ramus and inferior sacrum were found to have a low stiffness. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **CT Scan** & **Isotropic** & **Orthotropic** & **Orthotropic** & **Orthotropic** & **Orthotropic** & **Orthotropic** & **Orthotropic** \\  & **Model** & **Model** & **Model** & **Model** & **Model** & **Model** & **Model** & **Model** \\ \hline
10–1000 MPa & 26.32 & 63.83 & 86.33 & 91.45 & 89.37 & 71.89 & 81.79 \\
10–2000 MPa & 47.37 & 77.88 & 89.64 & 93.89 & 92.27 & 78.85 & 87.56 \\
10–3000 MPa & 59.48 & 84.23 & 91.44 & 95.10 & 93.74 & 82.57 & 90.43 \\
10–5000 MPa & 73.74 & 91.01 & 93.53 & 96.39 & 95.38 & 86.82 & 93.57 \\
10–10,000 MPa & 90.43 & 96.78 & 95.93 & 97.81 & 97.14 & 91.63 & 99.42 \\
10–15,000 MPa & 98.51 & 98.27 & 97.14 & 98.50 & 98.01 & 94.06 & 99.97 \\
10–18,000 MPa & 99.91 & 100.00 & 100.00 & 100.00 & 100.00 & 100.00 & 100.00 \\ \hline Mean (MPa) & 3727.6 & 1688.7 & 1059.4 & 616.4 & 781.9 & 2161.3 & 819.2 \\ Std. dev. (MPa) & 3817.5 & 3076.9 & 3411.5 & 2559.7 & 2898.7 & 4646.9 & 1841.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cumulative distribution (%) of elastic moduli of the three continuum models: CT scan derived, isotropic and orthotropic. Figure 3: Distributions of Young’s modulus (MPa) for the isotropic model (**a–c**), dominant Young’s modulus (**d–f**) and mean Young’s modulus (**g–i**) for the orthotropic model. The hybrid orthotropic model of the pelvis was found to converge after 44 iterations. The cortical thickness distribution is illustrated in Figure 4d-f. Thick shell elements appeared at the superior sacrum, around the sacroiliac joint, along the superior cubic ramus and in the region of the greater sciatic notch. Areas with thin shell elements were found on the superior ilium, inferior cubic ramus, ischial tuberosity and supraacetabular region. The distribution of mean and dominant Young's moduli of the continuum elements of the hybrid orthotropic model is shown in Figure 5d-i. Regions with high Young's moduli were found around the sacroiliac joint, on the arcuate line close to the sacrum, around the top of the sacrum, along the superior pubis ramus, around the superior acetabulum and between the posterior inferior iliac spine and greater sciatic notch. Low Young's moduli were found at the iliac fossa, ischial tuberosity, inferior sacrum and superior ilium, similar to the hybrid isotropic model. Similar to the distributions of the continuum models, distributions of dominant Young's moduli of the hybrid orthotropic model were visually more similar to the distributions of isotropic Young's moduli than the distributions of orthotropic mean Young's moduli. A structural model previously developed by the authors [39] was included in this comparison. Cortical thickness was highest at the superior sacrum, along the gluteal surface, around the sacroiliac joint, superior pubic ramus, posterior iliac crest and greater sciatic notch. Cortical bone had a thickness between 0.1 mm and 0.5 mm at the ischium, acetabulum, pubic tubercle, iliac fossa and posterior superior iliac spine (Figure 4g-i).