Fellow: Chad Hovey, PhD Mentors: Jean Heegaard, PhD; Gary S. Beaupré, PhD; and Felix E. Zajac, PhD Project Category: Arthritis - 2000 Wear of the polyethylene bearing surface is a significant factor limiting the longevity of total joint arthroplasty. Wear is a product of contact pressure and interface sliding, which are ultimately a result of human movement. To accurately quantify the stress and deformation of the arthroplasty, the stress analysis of the joint should reflect the dynamic environment of human motion. Many analyses utilize either rigid body gait models or deformable body joint models, but not both. Rigid body gait models can predict joint motion and forces, and help identify healthy and pathological movement. However, the rigid body assumption does not allow joint stress and deformation to be determined. Finite element models can produce joint stress and deformation, useful for predicting wear of arthroplasty. However, the boundary conditions are defined a priori and thus may not accurately reflect the loading encountered during dynamic activities such as walking and stairclimbing. In contrast to these two approaches, a coupled approach can be used to calculate rigid body motion and joint stress in a single analysis. The objective of this project is to develop a computational biomechanical model coupling a deformable diarthrodial joint to a dynamic model of human gait. The similarity in the dynamics of the coupled system to the purely rigid system indicates that deformation of the joint has a negligible effect on the dynamics of the gait. In addition to testing the assumptions of purely rigid models, the coupled framework could also validate purely deformable joint models to assure the applied loads are consistent with the dynamics of human motion. Coupling rigid and deformable body analysis can lead to a better understanding of how the dynamics of gait cause stress and deformation in joints. Publications: Hovey CB, Heegaard JH: Coupled Rigid-Deformable Body Formulation for Analysis of Joint Stress and Deformation During Gait. International Mechanical Engineering Congress and Exposition, Nov 14-19, Nashville, TN, 1999. Heegaard JH, Hovey CB: Hierarchical Models for Large Scale Simulations of the Musculoskeletal System. 4th International Symposium on Computer Methods in Biomedical Engineering, Oct 8-10, Lisbon, Portugal, 1999. Heegaard JH, Hovey CB: Coupling of a Rigid Multibody System with a Deformable Continuum Using an Augmented Lagrangian Formalism. Fifth U.S. National Congress on Computational Mechanics, Aug 4-6, Boulder, CO, 1999. Hovey CB, Heegaard JH, Beaupré GS, Zajac FE: Coupling Stress Analysis of Joints with Human Gait to Improve Wear Prediction in Joint Replacements. Second National Rehabilitation Research and Development Conference, Feb 20-22, Washington, DC, 2000. Funding Source: VA Pre-Doctoral Fellowship |
