Characterizing fluoroscopy based kinematic accuracy as a function of pulse width and velocity.
Fluoroscopic imaging has become increasingly popular to investigate total knee arthroplasty kinematics non invasively 3D implant models are aligned with 2D image projections, and optimized via an edge contour alignment technique. Previous studies have quantified the accuracy of this approach, however they do not always adequately address the impact of image collection parameters. A particularly sensitive parameter is the pulse width, or exposure time per frame. At longer pulse widths, more motion is captured in a single frame; this can lead to image blur and subsequent degradation to image edge quality. Therefore, the comparative accuracy of relative joint kinematics as a function of pulse width and joint velocity needs to be defined. A limits of agreement approach was taken to define the mean differences between optoelectric kinematic measures (gold standard) and fluoroscopic methods at various pulse widths (1, 8 and 16ms) and knee velocities (50, 100 and 225deg/s) The mean absolute differences between the optoelectric and fluoroscopic methods for 1ms pulse width were less than 1.5deg and 0.9mm. Comparable rotational differences (1.3deg) were observed for the 8ms pulse width but had larger translational differences (1.4mm) The 16ms pulse width yielded the greatest mean differences (2.0deg and 1.6mm) which increased with knee flexion velocity. The importance of pulse width and velocity should not be overlooked for future studies this parameter has proven to be a sensitive metric in the quantification of joint motion via fluoroscopy and must be identified and reported in future studies.
Journal of biomechanics