Dominance effect on scapula 3-dimensional posture and kinematics in healthy male and female populations

Abstract

Background: The contralateral shoulder is often used as a reference when evaluating a pathologic shoulder. However, the literature provides contradictory results regarding the symmetry of the scapular pattern in a healthy population. We assume that several factors including gender and type of motion may influence the bilateral symmetry of the scapulae.

Materials and methods: The dominant and nondominant shoulders of 2 populations of men and women comprising 11 subjects each were evaluated for 3 distinct motions: flexion in the sagittal plane, abduction in the frontal plane, and glenohumeral internal/external rotation with the arm abducted at 90°. Posture, kinematics, and range of motion were studied separately.

Results: Asymmetries are observed for motions performed in the frontal and sagittal plane but not for internal/external rotation with the arm abducted at 90°. For both male and female populations, multiplanar asymmetries are observed and the dominant scapula has a larger upward rotation. The asymmetries mainly originate in the scapula's kinematics and not in its original posture.

Conclusion: Small but significant asymmetries exist between the dominant and nondominant shoulders in terms of kinematics. One should be aware of these differences when using the contralateral shoulder as a reference.

Level of evidence: Basic science study, kinematics

Keywords: 3D; Scapula; dominance; gender; kinematics; posture; shoulder.