Assessing The Mechanical Behavior Of Treatments For Focal Articular Cartilage Lesions
In a healthy knee joint, articular cartilage (AC) supports loads, dissipates energy, and lubricates with little to no signs of wear or damage. With injury or degeneration related to osteoarthritis (OA), cartilage changes occur leading to significant loss of mechanical function, with the potential to cause further progressive degeneration of cartilage. While the connection between mechanical changes and arthritis progression is well known, previous work has focused primarily on bulk, tissue-scale ([ALMOST EQUAL TO]1mm) behavior. What is less clear is how mechanical behavior changes on the microscale (e.g. [ALMOST EQUAL TO]10-20[MICRO SIGN]m) during cartilage degradation. Previous work in our lab has developed techniques for measuring local strains in healthy cartilage via confocal elastography. This work focuses on applying traditional and novel techniques to understand the mechanical behavior at degraded and repaired articular cartilage. The first aim elucidates the fundamental relationships between the composition and structure of degraded cartilage and its local mechanical behavior, specifically its viscoelastic response with degeneration. This study combined state of the art techniques for analyzing cartilage structure, and high resolution mapping of mechanical properties on the microscale([ALMOST EQUAL TO]20[MICRO SIGN]m). This work provided new insight into structural and local mechanical changes that occur in cartilage during the early stages of OA. Due to its avascular nature, articular cartilage exhibits an extremely limited capacity to heal when damaged. Consequently, research dealing with cartilage repair strategies is of elevated importance. Restoring the mechanical properties of tissue at the repair site is a common problem in tissue engineering techniques aimed at repairing cartilage defects. Therefore, the second and third aims investigated the mechanical performance of repaired cartilage treated with either matrix membranes or growth factors to assist in tissue formation within a defect site and surrounding AC. The present work has developed into an innovative mechanical characterization technique. Specifically, combining the confocal elastography technique, with the unique sample populations from second and third aim to tackle a problem that has faced the orthopedic research field for more than two decades: understanding the mechanics of the interface between native and repaired cartilage. I've identified two distinct error modes of failure for this interface - sliding and peeling. As such, understanding the structure function relationship in healthy, damaged, and repaired cartilage, is critical for devising strategies to restore tissue impaired by injury or disease and can provide a template for successful implant design.
Articular Cartilage; Cartilage Repair; Confocal Elastography
Cohen,Itai; Nixon,Alan J
Ph. D., Biomedical Engineering
Doctor of Philosophy
dissertation or thesis