A moving fluoroscope to capture tibiofemoral kinematics during complete cycles of free level and downhill walking as well as stair descent

Abstract

Videofluoroscopy has been shown to provide essential information in the evaluation of the functionality of total knee arthroplasties. However, due to the limitation in the field of view, most systems can only assess knee kinematics during highly restricted movements. To avoid the limitations of a static image intensifier, a moving fluoroscope has been presented as a standalone system that allows tracking of the knee during multiple complete cycles of level- and downhill-walking, as well as stair descent, in combination with the synchronous assessment of ground reaction forces and whole body skin marker measurements. Here, we assess the ability of the system to keep the knee in the field of view of the image intensifier. By measuring ten total knee arthroplasty subjects, we demonstrate that it is possible to maintain the knee to within 1.8 ± 1.4 cm vertically and 4.0 ± 2.6 cm horizontally of the centre of the intensifier throughout full cycles of activities of daily living. Since control of the system is based on real-time feedback of a wire sensor, the system is not dependent on repeatable gait patterns, but is rather able to capture pathological motion patterns with low inter-trial repeatability.

Kinematic Evaluation of the GMK Sphere Implant During Gait Activities: A Dynamic Videofluoroscopy Study

“…Eight force plates (Kistler AG, Winterthur, Switzerland), which were fully decoupled from the surrounding floor, provided undisturbed ground reaction forces (GRFs) during all measured gait activities . A GRF threshold of 25 N was used to determine the gait events.…”

“…To image complete, consecutive cycles of the knee joint during level walking, downhill walking and stair descent, the moving fluoroscope was employed to capture the relative movements of the femoral and tibial components with a measurement frequency of 25 Hz during the investigated gait activities . Detailed information about the videofluoroscopic image capture are provided in the literature …”

“…Eight force plates (Kistler AG, Winterthur, Switzerland), which were fully decoupled from the surrounding floor, provided undisturbed ground reaction forces (GRFs) during all measured gait activities. 26 A GRF threshold of 25 N was used to determine the gait events. The trajectories of a heel marker, captured using an optoelectronic system consisting of 22 infrared cameras (Vicon MX system; Oxfords Metrics Group, Oxford, UK), were used to define the second heel strike event of downhill walking, which was not instrumented with a force plate.…”

“…To image complete, consecutive cycles of the knee joint during level walking, downhill walking and stair descent, the moving fluoroscope was employed to capture the relative movements of the femoral and tibial components with a measurement frequency of 25 Hz during the investigated gait activities. 26,27,29 Detailed information about the videofluoroscopic image capture are provided in the literature. 26,27,[29][30][31][32][33] Data Processing Two-dimensional/three-dimensional (2D/3D) registration The acquired digital images were corrected for distortion using a local correction algorithm based on a reference grid.…”

“…Imaging studies have allowed a detailed analysis of the in vivo internal tibio‐femoral kinematics throughout knee flexion, but are generally limited in the examination field of view, and therefore do not allow tracking of the knee joint during full cycles of dynamic gait activities, or are restricted to imaging only a portion of the whole motion. To overcome the constraints of such static imaging approaches, dynamic systems have been developed that now allow investigation into tibio‐femoral kinematics throughout complete cycles of level walking, downhill walking, and stair descent. The use of such a system has, for the first time, recently shown that tibio‐femoral kinematics depend on the activity performed and that clear differences between the loaded stance and the unloaded swing phases of gait activities exist .…”