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Since the longevity of an orthopaedic implant depends on the integrity of the bone/implant interface, knowledge of factor influencing the time course of tissue differentiation surrounding an implant will be important for improved implant design strategies. The relative influences of motion, loading, implant surface coating and roughness, and biologic growth factors, are not known. The ability to computationally model and predict this differentiation of bone tissue and the bone/implant interface, will be influential in focusing the next level of rational implant design refinement.

Professor Joan Bechtold of the Orthopaedic Surgery Department at the University of Minnesota is working to optimize the accuracy and predictive power of computational models of adaptive tissue differentiation in bone, incorporating mechanical and biologic factors. The bone, implant, and surrounding gap in which the tissue differentiates is being analyzed using biphasic finite element modeling techniques. The role of biologic factors, and their interaction with the mechanical environment are examined through cytokine and growth factor network feedback relationships recently proposed in the computational biology literature. Experimental validation is provided by data obtained through pressures sensors attached to the test implant in a coordinated experimental effort.
Dr. Olivier Mouzin (left) and Dr. Pascal Swider (center) of the Laboratory of Biomechanics in Toulouse, France visit with Professor Joan Bechtold (right) of the Orthopaedic Surgery Department at the University of Minnesota.
Dr. Pascal Swider, from the Laboratory of Biomechanics in Toulouse, France traveled to Minneapolis to collaborate with Professor Bechtold on this project. His collaboration is dealing with the formulation of the numerical model strategy and implementation, as well as the design and interpretation of the experimental validation studies. As part of the numerical modeling, he will work with Dr. Olivier Mouzin, also of the Laboratory of Biomechanics in Toulouse, France, and Professor Bechtold to set the parameters and scope of the model. These discussions are most efficient when conducted in person, with the Supercomputing Institute's resources available for consult, and at the laboratory housing the experimental equipment and implants. As part of the experimental validation, Dr. Swider will work with refining the design of the microsensors embedded in the experimental implant. Again, it is important that these discussions take place with the other scientists who are fabricating and testing the sensors and with the other collaborators who are advising on telemetry and other factors related to their successful implementation. Dr. Swider's collaboration is integral to the conduct of this research, and, while electronic communication has allowed good progress toward the aims of this project, a series of focused meetings and discussions with all collaborators helps further foster this collaboration.
In order to facilitate the packaging and deployment of ultra-lightweight structures, this work aims to formulate the underlying principles that govern the theory of folding of thin structures to prove basic theorems that characterize the folding process and to develop a computational algorithm and graphical base for the establishment of an interactive design program. Dr. John Ernie Dunn of Scientific Consulting in Tempe, Arizona visited Professor Roger Fosdick of the Aerospace Engineering and Mechanics Department at the University of Minnesota to collaborate on this work. Their project is initially concerned with the folding of material surfaces as utilized in inflatable antennae and solar sails technology, but they also have a basic interest in the folding of space-frame networks in general.

Major aspects of this program currently being considered include both the geometric and kinematic foundations of the folding problem and the kinetics and the consequent material behavior associated with force, moment, and energy expenditures at the fold points and fold lines. The main issues of the first part are related to the questions of local and global compatibility.
Graduate student researcher Eric Petersen (left), Dr. John Ernie Dunn (center) from Scientific Consulting in Tempe, Arizona, and Professor Roger Fosdick (right) of the Aerospace Engineering and Mechanics Department at the University of Minnesota.

 

This information is available in alternative formats upon request by individuals with disabilities. Please send email to alt-format@msi.umn.edu or call 612-624-0528.
 

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