Related Experiment Video
Updated: Mar 13, 2026
In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
Published on: July 2, 2021
Characterizing fluoroscopy based kinematic accuracy as a function of pulse width and velocity.
Arin M Ellingson1, Joseph D Mozingo2, Dixon J Magnuson3
1Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, USA; Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, USA; Department of Rehabilitation Medicine, University of Minnesota, Minneapolis, MN, USA.
Fluoroscopic imaging accuracy for knee replacement analysis depends on image pulse width. Shorter pulse widths (1ms) provide more precise joint motion measurements than longer ones (16ms), especially at higher knee velocities.
Area of Science:
- Biomedical Engineering
- Orthopedic Surgery
- Medical Imaging
Background:
- Fluoroscopy is a common non-invasive method for assessing total knee arthroplasty (TKA) kinematics.
- Current methods align 3D implant models with 2D projections but may not fully account for image acquisition parameters.
- Image pulse width (exposure time per frame) can significantly impact image quality and kinematic accuracy due to motion blur.
Purpose of the Study:
- To determine the comparative accuracy of fluoroscopic TKA kinematics measurement across different pulse widths and knee velocities.
- To define the impact of pulse width on the accuracy of relative joint kinematics compared to an optoelectric gold standard.
Main Methods:
- A limits of agreement approach was used to compare fluoroscopic kinematic data with optoelectric measurements.
- Experiments were conducted at varying pulse widths (1ms, 8ms, 16ms) and knee flexion velocities (50°/s, 100°/s, 225°/s).
Main Results:
- The 1ms pulse width showed minimal mean absolute differences (rotational: <1.5°, translational: <0.9mm).
- The 8ms pulse width had comparable rotational accuracy (1.3°) but increased translational differences (1.4mm).
- The 16ms pulse width resulted in the largest mean differences (2.0° and 1.6mm), with accuracy decreasing at higher velocities.
Conclusions:
- Image pulse width is a critical parameter affecting the accuracy of fluoroscopic TKA kinematics.
- Shorter pulse widths are recommended for more precise kinematic quantification.
- Pulse width and velocity should be reported in future fluoroscopic kinematic studies.
