BME PhD Candidate Kyle D. Meadows will be defending his dissertation:


MRI Based Non-Invasive Detection and Monitoring of Tissue Mechanics and Degenerative Changes in the Intervertebral Disc and the Meniscus



Degeneration and injury of fibrocartilages are often implicated in painful musculoskeletal conditions, which cause the most years lived with disability worldwide. Low back pain (LBP) and osteoarthritis (OA) rank 1st and 2nd among musculoskeletal conditions, based on global burden of disease data. Additionally, spine and knee surgeries are among the most common orthopedic procedures every year. Disc and meniscus injuries are linked to higher rates of LBP and OA, respectively, but questions remain regarding the direct cause of this correlation. Fibrocartilage degeneration is currently evaluated via structural assessment of magnetic resonance images (MRI), but many people with degenerative tissues do not have pain. It is hypothesized that pain may be more closely linked to tissue function as opposed to structural degeneration. Invasive assessment of disc function has shown better specificity for identification of pain causing discs, and LBP is often exacerbated or abated by different postural positions. Similarly, work in the knee has suggested that mechanics may be better at detecting painful joints than tissue structure. Ex vivo testing of cadaveric tissues informs us that degenerate or injured tissues have altered mechanics, likely leading to altered joint kinematics in vivo, but these explant studies do not match the in vivo boundary conditions. In vivo measurement of tissue function is still in its infancy. Development of in vivo assessment of tissue function may provide better context as to why these injuries lead to pain and what therapies and repairs should be targeting to remedy the situation.

The objective of this thesis was to develop and apply methods for non-invasive measurement of function and degeneration of the intervertebral disc and meniscus that could be used to inform and direct clinical decisions related to aging and injury. First, I identified appropriate sequence parameters to acquire MR data and applied curve fitting methods to accurately calculate disc T2 in the presence of image signal noise (Aim 1). I then developed methods and analyses to evaluate the mechanical function of the discs via noninvasive MRI in a young, asymptomatic cohort to establish baseline in vivo disc mechanics (Aim 2). Next, knee joint kinematics were assessed in intact joints, following root tear, and following suture repair at an acute time point under physiological loading using novel MRI methods (Aim 3). Finally, similar methods were applied to a porcine model of meniscus injury to appraise joint health and progression of degeneration following tear or repair in the short-term due to mechanical and biological interactions including endogenous remodeling and healing (Aim 4). In summary, this dissertation developed and utilized tools to evaluate in vivo mechanical function in the spine and knee in relation to structural degenerative changes. These tools may be used in the future to assess the progression of degeneration over time and to test the effectiveness of different repair and treatment strategies for disc and meniscus injury.