Dynamic rasterstereography improves the detection of movement delays and dynamic asymmetries in the scapulothoracic kinematic of healthy subjects

Abstract

Purpose: Assessing scapulothoracic kinematics typically involves visually observing patients during movement, which has limited inter- and intraobserver reliability. Dynamic rasterstereography (DRS) records, measures and visualizes surface structures in real time, using a curvature map to colour-code convex, concave and saddle-shaped structures on the body surface. This study aimed to evaluate the diagnostic efficacy of DRS-assisted observation in identifying dyskinetic scapulothoracic patterns.

Methods: Thirty-seven healthy participants performed shoulder abduction/adduction and flexion/extension cycles without additional weight, recorded using both DRS and a conventional video camera. A metronome ensured consistent timing, and for DRS a grid of parallel light rays projected onto the back surface was captured using indirect optical measurement techniques. The mean surface curvature was converted into a colour scale. The diagnostic performance of conventional and DRS videos in detecting dyskinetic patterns, including static asymmetries, dynamic asymmetries, motion delays and rapid compensatory movements, were compared. Two investigators independently evaluated the videos twice in a blinded and randomized sequence to assess intra- and interrater reproducibility.

Results: Analysis of 118 videos showed good-to-excellent intrarater and interrater reproducibility for both techniques (ICCs 0.727-0.949). Movement delays and dynamic asymmetries were observed more frequently when evaluating DRS videos rather than conventional videos (p = 0.0008 and p = 0.0016). However, no differences were found in static asymmetry and rapid compensatory movement detection.

Conclusions: DRS can create a real-time model of the trunk surface and allows observers to evaluate the scapular movements with good-to-excellent intrarater and interrater reproducibility; compared to clinical observation, some specific scapular motion alterations can be observed more frequently. Clinical Trial Registration: Part of the DRKS00022334 trial.

Level of evidence: Level II, prospective cohort study.

Keywords: augmented reality; physiotherapeutic interventions; rasterstereography; reproducibility; scapula; scapular dyskinesis; scapulothoracic kinematics; stereography.

Figure 1

Schematic illustration of the setup featuring the DIERS 4Dmotion®Lab, which generates the rasterstereography recording by projecting a grid of light rays onto the subject's back surface. Subsequently, the recording unit measures the curvatures and the collected data are utilized to generate the dynamic recording. Additionally, a video camera captures a conventional recording for direct comparison purposes. Courtesy of DIERS International GmbH, Schlangenbad, Germany.

Figure 2

Demonstrative examples of optical and rasterstereography recordings during abduction. (a) Optical image capture of a subject at 90° of abduction. (b) Optical image capture of a subject approaching 180° of abduction. (c) Dynamic rasterstereography (DRS) image capture of a subject at 90° of abduction. (d) DRS image capture of a subject approaching 180° of abduction.

Figure 3

Bar charts comparing different study outcomes between conventional and dynamic rasterstereography‐augmented videos. The y‐axis indicates the study outcome frequency. ***p < 0.001; **p < 0.01; *p < 0.05.

Figure 4

Pie charts illustrating the frequency of movement delays detected during two different moments of the scapular motion cycle.

Figure 5

Schematic illustration and pie charts depicting the frequency of rapid movements during the different phases of the scapular motion cycle.