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

Abstract

Although three-dimensional electromagnetic systems are widely used to evaluate the 3-dimensional scapular kinematics their reliability when testing bilateral upper extremity tasks is unknown. The purpose of this study was to investigate the repeatability of the scapular kinematic analyses using the Flock of Birds (FOB) system during bilateral upper extremity movements.

Twenty-one volunteers without shoulder problems were included (aged 24.8 years; body mass index averaged 21.2 kg/m(2)) to the study. Scapular internal-external rotation, upward-downward rotation, and anterior-posterior tilt was recorded during bilateral arm elevation on sagittal, scapular and frontal planes. Measurements were repeated at 5-7 days intervals. Intra-session and inter-session repeatability were determined using intraclass correlation coefficients (ICC) scores and standard errors of measurements (SEM).

The ICC scores were found to be 0.81 to 0.99 for intra-session measurements and 0.60 to 0.83 for inter-session measurements. The SEM scores were 0.8 degrees-3.4 degrees and 2 degrees-7.2 degrees for the intra and inter-session measurements respectively.

The repeatability of the FOB system was excellent for the intra-session measurements, but it was weaker for the inter-session measurements. These results support the use of the FOB system for assessing scapular orientation but the analyses should be conducted more carefully when it is applied to the longitudinal measurements.