Scapular kinematics during humeral elevation in adults and children

Background. Appropriate motion of the scapula is important for dynamic positioning of the glenoid during humeral elevation. A number of studies have described the typical scapular kinematics during humeral elevation in adults. However, children and adults may have differences in scapulothoracic musculature and scapular osteology. To our knowledge, no study has been performed examining scapular kinematics in children with either typical or atypical development. Consequently in children the influence of age and development on scapular motion is currently unknown. The aim of this study was to describe and compare the kinematic patterns of the scapula during humeral elevation in children with typical development and healthy adults. Methods. Fifteen adults, 7 females, 25-37 years of age, and 14 children, 8 females, 4-9 years of age, participated in this study. Kinematic data were collected using a magnetic tracking device. Subjects were asked to elevate their arm in the scapular plane (40°anterior to the frontal plane) in a sequence of three trials. Findings. Significant differences were seen between the two age groups in the dependent variables. During scapular plane rotation from 25°to 125°, children showed greater upward rotation (43.9°SD 6.39°) than adults (29.1°SD 10.1°). The mean glenohumeral to scapulothoracic ratio in the scapular plane was 2.4:1 for adults, 1.3:1 for children. Interpretation. This study demonstrates that there are significant differences in scapular kinematic patterns between children and adults. Children have a greater contribution from the scapulothoracic joint, specifically upward rotation toward humeral elevation. From a clinical perspective, these results can be used to help determine the incorporation of stabilization and mobilization of the scapulothoracic joint during exercises for a child with impairment at the shoulder for improving shoulder function.