Three-Dimensional Quantitative Evaluation of the Scapular Skin Marker Movements in the Upright Posture

Abstract

Motion capture systems using skin markers are widely used to evaluate scapular kinematics. However, soft-tissue artifact (STA) is a major limitation, and there is insufficient knowledge of the marker movements from the original locations. This study explores a scapular STA, including marker movements with shoulder elevation using upright computed tomography (CT). Ten healthy males (twenty shoulders in total) had markers attached to scapular bony landmarks and underwent upright CT in the reference and elevated positions. Marker movements were calculated and compared between markers. The bone-based and marker-based scapulothoracic rotation angles were also compared in both positions. The median marker movement distances were 30.4 mm for the acromial angle, 53.1 mm for the root of the scapular spine, and 70.0 mm for the inferior angle. Marker movements were significantly smaller on the superolateral aspect of the scapula, and superior movement was largest in the directional movement. Scapulothoracic rotation angles were significantly smaller in the marker-based rotation angles than in the bone-based rotation angles of the elevated position. We noted that the markers especially did not track the inferior movement of the scapular motion with shoulder elevation, resulting in an underestimation of the marker-based rotation angles.

Simulated Increase in Monoarticular Hip Muscle Strength Reduces the First Peak of Knee Compression Forces During Walking

“…Nakano et al (2020) reported even higher errors during throwing with up to 47.3 mm for elbow joint center with equivalent method and materials. Comparably, marker movement distance for scapula markers in elevated position ranged from 30.4 to 70.0 mm (Yoshida et al 2022). Considering our results were preliminary work on uniform population, they highlighted the potential of accuracy and versatility of our method if the improvements raised are addressed and applied to a more diverse cohort.…”

A Method to Track 3D Knee Kinematics by Multi-Channel 3D-Tracked A-Mode Ultrasound

“…This approach could effectively mitigate the effects of soft tissue artifacts (STAs). In systems using skin-mounted markers, STAs are typically present and challenging to eliminate due to the inherent mismatch between skin and bone movement [ 28 , 29 , 30 ]. For instance, the reported accuracy of such systems for walking motion tasks shows average errors up to 4.40° and 13.0 mm for rotations and translations, respectively [ 31 ].…”