Time: 12:40 - 13:00
The pelvic construct is an important part of the body as it facilitates the transfer of upper body weight to the lower limbs and protects a number of organs and vessels in the lower abdomen. In addition, the importance of the pelvis is highlighted by the high mortality rates associated with pelvic trauma. Although computational models of the pelvis have been used to assess its structure or behaviour under loading, no attempt has been made to develop a model using a structural mechanics approach as opposed to a continuum mechanics approach. This study presents a comparison between a mesoscale structural model and a continuum orthotropic model of the pelvic construct and the joints and ligaments associated with it. For the first model, shell elements were used to model cortical bone, while truss elements were used to model trabecular bone and the ligaments and joints. The continuum model was developed using shell elements to represent cortical bone, solid tetrahedral elements to represent trabecular bone and truss elements to represent the ligaments and joints.
Both finite element models were subjected to an iterative optimisation process based on a strain driven bone adaptation algorithm [1, 2]. The pelvis models were adapted to a number of common daily living activities (walking, stair ascent, stair descent, sit-to-stand and stand-to-sit) by applying joint, muscle and inertial loads derived using a musculoskeletal modelling framework. The cortical thickness distribution and trabecular architecture of the adapted models were compared qualitatively with computed tomography scans. A third model derived directly from the CT scans was used as a benchmark to compare the response of the adapted models for a load case corresponding to standing up.
Both models have shown good agreement with the CT images in terms of overall bone architecture. The comparison between a structural and a continuum model is useful as it highlights a number of potential advantages of using the former approach. The structural modelling approach was shown to be less computationally demanding and it enables a number of applications such as fracture modelling, design and additive manufacturing of frangible surrogates. In addition, the structural model could be developed further by assigning the elements an initial directionality derived from the elasticity matrices associated with elements of the continuum model.