Scapular kinematics in adolescent idiopathic scoliosis: A three-dimensional motion analysis during multiplanar humeral elevation

The scapula plays a critical role in supporting shoulder function. Considering the closed anatomical relationship between the scapula and the thoracic cage, the presence of postural disturbances could be linked to alterations in the scapular position and orientation in adolescent idiopathic scoliosis (AIS). However, currently there is a lack of descriptive research and detailed assessment of scapular kinematics in AIS. The aim of this study was to investigate the three-dimensional scapular kinematics in AIS. Nineteen AIS patients and fourteen healthy controls participated in this study. Bilateral shoulder kinematics were measured with an electromagnetic tracking device during shoulder elevation in the sagittal, scapular, and frontal planes. Data for the scapular orientation were analyzed in the resting position and at 30°, 60°, 90°, and 120° of humerothoracic elevation. Scapular behavior was different in participants with AIS, compared to healthy controls, with different patterns observed on convex and concave sides. While examining all three planes of elevation, the scapula was more internally and anteriorly tilted on the convex side, while the scapula was more externally, downwardly rotated, and posteriorly tilted on the concave side in participants with AIS. Furthermore, there was a decreased peak humerothoracic elevation and altered scapular posterior tilt in participants with AIS in the resting position. These findings increase our knowledge and understanding of scapular alterations and the reported scapular alterations can be considered as adaptive compensation strategies in AIS.