Mechanical Engineering - Theses
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ItemEnhancement and evaluation of a mobile biplane X-ray imaging system( 2016)Accurate in vivo measurement of three-dimensional (3D) knee joint kinematics during locomotion is important for understanding knee joint function and for evaluating the performance of total knee arthroplasty (TKA) design and surgical procedures. The most accurate non-invasive method for measuring dynamic knee joint kinematics is biplane X-ray fluoroscopy. Current biplane fluoroscopy systems are stationary and impose restrictions on the measurement of joint kinematics during dynamic activity, making it necessary for subjects to walk on a treadmill, regardless of the potential differences in knee joint kinematics between treadmill and overground walking. In the Biomotion Laboratory at the University of Melbourne, a novel mobile biplane X-ray (MoBiX) imaging system was designed and built to track the knee and measure knee joint kinematics during overground walking. Prior to the present thesis, the MoBiX system was capable of translating the two X-ray units mounted on a custom robotic gantry mechanism to replicate predefined sagittal-plane knee trajectories during overground walking. The main objectives of the present thesis were threefold: first, to enable the MoBiX imaging system to track movement of the knee and calculate knee joint kinematics during overground walking; second, to establish the accuracy of knee joint kinematic measurements obtained from the MoBiX system; third, to acquire 3D knee joint kinematics for TKA patients for one complete cycle of overground walking and to quantify differences in knee joint kinematics between treadmill and overground walking. In the present thesis, methodologies as well as the associated hardware and software were developed and implemented to enhance the MoBiX imaging system. Specifically, a joint motion tracking system was developed to enable the MoBiX system to track and image the knee concurrently during overground walking. A four-step procedure was developed in accordance with methodologies commonly adopted in the literature to facilitate the extraction of knee joint kinematics from biplane X-ray images acquired by the MoBiX imaging system. Three benchmark experiments were designed and conducted to evaluate the accuracy with which the MoBiX imaging system measures 3D dynamic knee joint kinematics during overground walking. In vivo experiments were conducted on 10 TKA patients to acquire 3D knee joint kinematics during a complete cycle of overground walking, as well as to quantify the differences between treadmill and overground walking. Experimental results indicated that measurement accuracy was enhanced by tracking and imaging the knee concurrently during gait. Maximum RMS errors were 0.33 mm and 0.65°, respectively, for the relative translations and rotations between the tibial and femoral components of a TKA implant, and 0.78 mm and 0.77° for the relative translations and rotations between the tibia and femur in an intact knee. The 3D knee joint kinematics corresponding to treadmill walking did not closely represent overground walking, and significant differences were observed in the temporospatial gait parameters, 6DOF knee joint kinematics, articular joint contact and implant wear predictions.