Validating scapular motion measurements using an optical motion analyzer and gravity magnetic resonance imaging

[Purpose] This study aimed to validate whether scapular motion measured using a pad with retroreflective markers and optical motion analyzer (VICON MX) can reflect the motion calculated by images using multi-posture (gravity) magnetic resonance imaging. [Participants and Methods] The participants were 12 healthy males (12 dominant-side shoulders). The measurement items were the scapular angle at shoulder flexion 140° and 160° and abduction 100°, 120°, 140°, and 160°. The scapular angle changes were extracted from the upward/downward and internal/external rotations. Angular changes were calculated by subtracting the scapular angle in static position (drooped upper limb and external shoulder rotation) during resting chair sitting from the scapular angle in each of the six limb positions and subtracting it at shoulder abduction 100° from the scapular angle at shoulder abduction 120°, 140°, and 160°. [Results] The results showed no agreement in most cases and no consistent bias. [Conclusion] The result questions the validity of scapular motion analysis using pads with optical markers. However, the facility environment imposes many study limitations, and this method requires further validation eventually.