Bone metastasis to the spine, pelvis or hip in patients with prostate cancer is a pathology that occurs in approximately 80% of cases. Metastases in the spine can cause pain, instability and neurological injuries. Therefore, it is relevant to evaluate when critical conditions have been reached and the structural integrity of the bone is compromised. Numerical methods based on patient data, obtained through post-processing of medical images, provide a tool to model the complexity of the biological tissue material. Computed axial tomography (CT) together with segmentation tools allows the reconstruction of 3D bone models that include mechanical properties, and that represents the anisotropic condition of bone structures. In this work, we present the L5 lumbar vertebra model of a patient affected by metastases and evaluate biomarkers to indicate the level of damage, compared with the reference case of healthy bone in an initial stage.

The present research proposes a methodology to determine the strength of a spinal bone in patients who suffer from prostate cancer using diagnostic imaging, with the purpose of verifying if metastasis has occurred, and critical conditions have been reached. Advanced numerical methods allow the modelling of anisotropic materials for different applications in biomedical engineering. The computed tomography images (CAT) provide the information to create a 3D model of the bone, in this case, the lumbar vertebra L5. Using segmentation software, it is possible to identify the mechanical properties of the materials that form the bone and define anisotropic conditions. The 3D anisotropic model is evaluated using finite element analysis (FEA), considering the appropriate boundary conditions and its respective material properties, and compared with the reference case of a healthy bone in an initial stage to assess the damage. Indicators based on the changes in stiffness of the vertebra could provide evidence of the need for chirurgical intervention.

In this work, the behaviour of a palm fruit bunch press shaft is investigated, which has presented early failure several times, not reaching its expected lifetime. The study allows determining the failure mode of the shaft by using the finite element method (FEM). The model is used to estimate the load produced by the fruit bunches over the worm screw and transferred to the shaft. Geometrical analysis of the shaft shape helps to determine failure mode. The stress and strain fields are obtained to determine the critical points of the design, in order to propose modifications to the shaft design. Moreover, after a short time of operation, the structure presented plastic deformation, the hexagonal shape in the shaft is repaired using a welding procedure, as showed metallographic and hardness results obtained on surface and subsurface level of the affected area for the fractographic analysis. This is compared with a raw steel SAE AISI 4340 under tempered like original condition.