Development of a fluoroscopic radiostereometric analysis system with an application to glenohumeral joint kinematics.

摘要

Ideally, joint kinematics should be measured with high accuracy, void of skin motion artefact, in three dimensions, and under dynamic conditions. Radiostereometric analysis (RSA) has the potential to fulfill all of these requirements. The objectives of this thesis were (1) to implement and validate a fluoroscopy-based RSA system, (2) to determine the effect of varying the calibration frame, (3) to correct image distortion, (4) to investigate errors in coordinate system creation for glenohumeral (shoulder) joint kinematics, (5) to introduce a new coordinate system definition for the scapula with limited radiation exposure, and (6) to use RSA to examine glenohumeral joint motions in-vivo..;Images were digitized and RSA reconstruction was performed using custom-written software. Images taken using fluoroscopy under ideal conditions can produce reconstructions that are as accurate as those taken with digital radiography, with standard errors of measurement of 43 mum and 0.23° and 36 mum and 0.12°, respectively. RSA is more accurate than optical tracking for rigid body motion. The fluoroscopes may be positioned at angles less than 135° without affecting the accuracy of reconstruction. A global polynomial approach to distortion correction is appropriate for use with RSA; however, the polynomial degree must be determined for each system with an independent accuracy measure.;An alternative scapular coordinate system was introduced to decrease the required radiation exposure for coordinate system creation by approximately half. The kinematic angles obtained using the alternative coordinate system were different from those obtained using the International Society of Biomechanics standard; however, the differences are not clinically significant.;As a first clinical application, glenohumeral joint translation was examined. The preliminary data suggests that humeral head position does not differ in active and static joint positioning.;An RSA system consisting of two portable C-arm fluoroscopy units and two personal computers was assembled. Calibration was performed using a custom-made calibration frame.;Fluoroscopy allows subjects to be examined while in motion and should enable substantial improvements to the study of even subtle in-vivo kinematics. It is likely that the RSA system will lead to an increased understanding of the effects of disease progression, surgical techniques and rehabilitation protocols on joint motion.;Keywords: fluoroscopy; radiostereometric analysis (RSA); calibration; distortion correction; scapula coordinate system; kinematics.