The repeatability of 3-dimensional scapular kinematic analysis during bilateral upper extremity movements

Area of Science:

• Biomechanics
• Kinesiology
• Orthopedics

Background:

• Three-dimensional electromagnetic systems are commonly used for analyzing scapular kinematics.
• The reliability of these systems for bilateral upper extremity tasks remains largely uninvestigated.

Purpose of the Study:

• To assess the repeatability of scapular kinematic analysis using the Flock of Birds (FOB) system.
• To evaluate the FOB system's reliability during bilateral upper extremity movements.

Main Methods:

• Twenty-one healthy volunteers participated in the study.
• Scapular rotations (internal-external, upward-downward) and tilt (anterior-posterior) were measured during bilateral arm elevation.
• Measurements were repeated within-session and across 5-7 day intervals, analyzed using intraclass correlation coefficients (ICC) and standard errors of measurements (SEM).

Main Results:

• Intra-session ICC scores ranged from 0.81 to 0.99, indicating excellent repeatability.
• Inter-session ICC scores ranged from 0.60 to 0.83, indicating weaker repeatability.
• Standard errors of measurements (SEM) were 0.8°-3.4° for intra-session and 2°-7.2° for inter-session measurements.

Conclusions:

• The FOB system demonstrates excellent intra-session repeatability for scapular orientation assessment.
• Inter-session repeatability is weaker, suggesting caution is needed for longitudinal measurements.
• The FOB system is suitable for assessing scapular orientation, but longitudinal studies require careful consideration of measurement intervals.