A model of uni-compartmental osteoarthritis and experimental measurements of material properties of cartilage
Date
2005
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Publisher
University of Delaware
Abstract
Osteoarthritis is a degenerative joint disease that affects more than 20 million people in the United States. It causes pain, loss of function, and costs the economy more than 60 billion dollars per year. The disease is characterized by the degeneration of articular cartilage, the smooth thin tissue that covers the ends of articulating bones. The function of articular cartilage is to provide wear resistance, maintain joint lubrication, and minimize contact stresses by supporting and distributing loads through the joint. Increased understanding of the mechanical environment of the tissue may provide insight into the mechanisms involved in the progression of osteoarthritis. ☐ Numerous animal studies to induce osteoarthritic changes and identify the biological and mechanical changes resulting from disease progression have been used. Previous research has presented useful information about the response of articular cartilage to traumatic injury; however there is very little research that permits disease progression without traumatic intervention. For this reason a novel altered joint loading device has been developed to induce uni-compartmental osteoarthritis. The device was developed to apply a varus or adduction moment to the knee of a rabbit specimen in vivo. The device was successful in applying and maintaining the desired moment regardless of configuration. Dynamic loading of the medial compartment of the knee is believed to contribute to the progression of knee osteoarthritis. ☐ To characterize the structure and function of articular cartilage and the underlying subchondral bone, micro-computed tomography scans and creep indentation experiments were performed on healthy rabbit specimens. The experimental data was analyzed using two separate models. Material properties were obtained from a finite element model and a numerical algorithm based on the analytical solution of the linear biphasic model. Comparisons were made between the material properties resulting from the two models, as well as between the twelve locations that were tested on each knee. ☐ Another active area of research is tissue engineering, which strives to develop cultured tissue that is phenotypically and mechanically similar to native healthy tissue. Experiments were performed to characterize the material properties of a cultured cartilage tissue equivalent (CTE) using one-dimensional confined compression stress relaxation experiments. Two separate studies were performed; first a developmental study to quantify how material properties differ at various culture times resulted in a difference in stiffness between two groups. A mechanical stimulation study then determined the mechanical effect of hydrostatic pressure applied to a CTE during culture. Mechanical stimulation improved the CTE’s material properties.