Low back pain (LBP) is a common and costly musculoskeletal disorder. Clinicians and researchers frequently assess dysfunction in LBP by observing patient's movement quality during pre-determined tasks using technically challenging and expensive motion capture devices. However, the cost and expertise needed to use these devices are direct barriers to their widespread adoption in clinical settings where direct benefits could be realized by LBP patients. RGB-D cameras are a potential inexpensive

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... d less time-intensive motion capture alternative, which have been validated for analyses of gait, postural control, ergonomics, and human anatomy. However, as manufactured, RGB-D cameras are not ready for specific kinematic analyses, such as lumbar spine motion, as the native artificial intelligence (AI) models do not adequately detect the number and location of trunk joints to accurately track three-dimensional kinematics. In this thesis a proof of concept framework to adapt RGB-D cameras to accurately measure lumbar spine kinematics is presented, which is separated into two research studies: 1) validation of an RGB-D depth-based algorithm against an optoelectronic motion capture system of reference for measuring spine motion, and 2) the development of a markerless method of measuring lumbar spine kinematics. In study one, 12 healthy young adults (6M, 6F) performed 35 cycles of repetitive flexion-extension with infrared reflective marker clusters placed over their T10-T12 spinous processes and sacrum, while motion capture data were recorded simultaneously by one RGB-D camera and a 10-camera optoelectronic motion capture system. Lumbar spine joint angle range of motion (ROM) were extracted and compared between systems. Root mean squared error (RMSE) values were very low across all movement axes (RMSE ≤ 2.05° ± 0.97°), and intraclass correlations (ICCs) were considered excellent across all axes (ICC2,1 ≥ 0.849), while Bland-Altman plots revealed that, on average, the RGB-D camera slightly underestimated flexion-extension an [...]