Abstract
The clinical uptake and influence of gait analysis has been hindered by inherent limitations of marker-based motion capture systems, which have long been the standard method for the collection of gait data including kinematics. Markerless motion capture offers an alternative method for the collection of gait kinematics that presents several practical benefits over marker-based systems. This work aimed to determine the reliability of lower limb gait kinematics from video based markerless motion capture using an established experimental protocol for testing reliability. Eight healthy adult participants performed three sessions of five over-ground walking trials in their own self-selected clothing, separated by an average of 8.5 days, while eight synchronized and calibrated cameras recorded video. Three-dimensional pose estimates from the video data were used to compute lower limb joint angles. Inter-session variability, inter-trial variability, and the variability ratio were used to assess the reliability of the gait kinematics. Compared to repeatability studies based on marker-based motion capture, inter-trial variability was slightly greater than previously reported for some angles, with an average across all joint angles of 2.5°. Inter-session variability was smaller on average than all previously reported values, with an average across all joint angles of 2.8°. Variability ratios were all smaller than those previously reported with an average of 1.1, indicating that the multi-session protocol increased the total variability of joint angles by 10% of the inter-trial variability. These results indicate that gait kinematics can be reliably measured using markerless motion capture.
Highlights
Three-dimensional (3D) human movement analysis is a widely used tool in clinical and research biomechanics to provide comprehensive 3D representations and quantification of individuals’ movement patterns, gait
The use of Theia3D to calculate joint kinematics removed the reliance on an experienced examiner to identify anatomical landmarks and accurately place markers, substantially reduced the time to collect data, and resulted in kinematic data that was reliable between sessions on separate days
The average inter-session variability measured in this study (2.5°) was the smallest across all other studies (3.1°-3.3°), indicating that measuring gait kinematics across multiple sessions using Theia3D introduces less variability compared to field-accepted marker-based motion capture systems
Summary
Three-dimensional (3D) human movement analysis is a widely used tool in clinical and research biomechanics to provide comprehensive 3D representations and quantification of individuals’ movement patterns, gait This tool allows comparisons to be made within and between individuals and groups on a singular or longitudinal basis, providing quantified measures of functional musculoskeletal health. Marker-based motion capture has several inherent flaws that affect a researcher or clinician’s ability to collect repeatable measures of gait, over multiple visits These limitations include lengthy data collection times, the requirement of highly skilled experimenter capable of accurate marker placement, dedicated laboratory space, and the intrusive nature of the technology and experimental protocols on the subject or patient, which in turn limit the use of this data in clinical decision-making (Narayanan, 2007; Benedetti et al, 2017). The unfamiliar laboratory environment, physical and social discomfort due to the clothing and markers, and requests to perform natural gait on demand reduce the fidelity of gait data collected using marker-based motion capture and negatively affect recruitment rates
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