Characterizing the Mechanical Behaviour of the Human Pelvis Through Finite Element Analysis

In the human musculoskeletal system, the pelvis functions as a crucial transfer point for upper body loads to the lower extremities. Existing treatments in the field of pelvic reconstructive surgery do not account for versatile structural differences in pelvic geometries and variations in pelvic bone properties. This thesis aims to develop a novel approach to facilitate and automate the creation of multiple specimen-specific finite element (FE) models of the pelvis and to utilize these models to characterize mechanical behavior of the pelvis, under healthy and pathologic conditions. Robust generation of pelvic FE models is necessary to understand variations in mechanical behaviour resulting from differences in gender, aging, disease, and injury. A new semi-automated landmark-based FE morphing and mapping approach was developed for pelvic FE model generation without the need for segmentation. A cohort of specimen-specific pelvic FE models was generated using the new approach and the models were validated against experimental data in double leg stance configuration. The validated cohort of specimen-specific pelvic FE models was utilized to examine pelvic strains at different phases of the gait cycle (double leg stance, heel-strike/heel-off and midstance/midswing). The FE models revealed that the strain patterns throughout the pelvic structure between the double leg stance and heel-strike/heel-off configurations are not significantly different, whereas a significant difference was found in the midstance/midswing configuration. The morphing methodology was further extended to generate pelvic FE models of different shapes and to analyze their biomechanical behaviour. A significant difference was found in the strain patterns between the android (classic male shape) and gynecoid (classic female shape) pelvises. Finally, a specimen-specific pelvic FE model of an open book fracture was developed and validated against experimental data. The strain patterns identified in the fractured model aligned with the clinical understanding of open book fracture pathology. Overall, the findings of this thesis provide new understandings into the complex biomechanical behaviour of the human pelvis. This work creates a platform for more complex future FE modeling investigations to continue to study the behaviour of this multifaceted skeletal structure.Ph.D

Analysis of pelvic strain in different gait configurations in a validated cohort of computed tomography based finite element models

The pelvis functions to transmit upper body loads to the lower limbs and is critical in human locomotion. Semi-automated, landmark-based finite element (FE) morphing and mapping techniques eliminate the need for segmentation and have shown to accelerate the generation of multiple specimen-specific pelvic FE models to enable the study of pelvic mechanical behaviour. The purpose of this research was to produce an experimentally validated cohort of specimen-specific FE models of the human pelvis and to use this cohort to analyze pelvic strain patterns during gait. Using an initially segmented specimen-specific pelvic FE model asa source model, four more specimen-specific pelvic FE models were generated from target clinical CT scans using landmark-based morphing and mapping techniques. FE strains from the five models were compared to the experimental strains obtained from cadaveric testing via linear regression analysis, (R2 values ranging from 0.70 to 0.93). Inter-specimen variability in FE strain distributions was seen among the five specimen-specific pelvic FE models. The validated cohort of specimen-specific pelvic FE models was utilized to examine pelvic strains at different phases of the gait cycle. Each validated specimen-specific FE model was reconfigured into gait cycle phases representing heel-strike/heel-off and midstance/midswing. No significant difference was found in the double-leg stance and heel-strike/heel-off models (p=0.40). A trend was observed between double-leg stance and midstance/midswing models (p=0.07), and a significant difference was found between heel-strike/heel-off models and midstance/midswing models (p=0.02). Significant differences were also found in comparing right vs. left models (heel-strike/heel-off p=0.14, midstance/midswing p=0.04).This study was supported by the Natural Sciences and Engineering Research Council, the Ontario Graduate Scholarship program, the High Performance Facility at the Centre for Computational Biology at the Hospital for Sick Children, Toronto, Ontario, Canada and SciNet, University of Toronto, Toronto, Ontario, Canada

Analysis of pelvic strain in different gait configurations in a validated cohort of computed tomography based finite element models

The pelvis functions to transmit upper body loads to the lower limbs and is critical in human locomotion. Semi-automated, landmark-based finite element (FE) morphing and mapping techniques eliminate the need for segmentation and have shown to accelerate the generation of multiple specimen-specific pelvic FE models to enable the study of pelvic mechanical behaviour. The purpose of this research was to produce an experimentally validated cohort of specimen-specific FE models of the human pelvis and to use this cohort to analyze pelvic strain patterns during gait. Using an initially segmented specimen-specific pelvic FE model asa source model, four more specimen-specific pelvic FE models were generated from target clinical CT scans using landmark-based morphing and mapping techniques. FE strains from the five models were compared to the experimental strains obtained from cadaveric testing via linear regression analysis, (R2 values ranging from 0.70 to 0.93). Inter-specimen variability in FE strain distributions was seen among the five specimen-specific pelvic FE models. The validated cohort of specimen-specific pelvic FE models was utilized to examine pelvic strains at different phases of the gait cycle. Each validated specimen-specific FE model was reconfigured into gait cycle phases representing heel-strike/heel-off and midstance/midswing. No significant difference was found in the double-leg stance and heel-strike/heel-off models (p=0.40). A trend was observed between double-leg stance and midstance/midswing models (p=0.07), and a significant difference was found between heel-strike/heel-off models and midstance/midswing models (p=0.02). Significant differences were also found in comparing right vs. left models (heel-strike/heel-off p=0.14, midstance/midswing p=0.04).This study was supported by the Natural Sciences and Engineering Research Council, the Ontario Graduate Scholarship program, the High Performance Facility at the Centre for Computational Biology at the Hospital for Sick Children, Toronto, Ontario, Canada and SciNet, University of Toronto, Toronto, Ontario, Canada