Assessment of three-dimensional rotation of the shoulder complex and scapulohumeral rhythm during sagittal movement

BACKGROUND: Due to the influence of spinal and respiratory movements, it is difficult to accurately measure the range of motion of each joint. OBJECTIVE: To conduct a three-dimensional (3D) measurement of each joint in the shoulder complex in different postures in the sagittal plane of the upper extremity. METHODS: Thirteen healthy adults with no history of shoulder surgery for trauma or chronic pain were enrolled in the present study. The computed tomography (CT) imaging data of the shoulder complex were acquired in four postures via the reconstruction and alignment of 3D images. The angles of the postural changes were measured, and rotation vectors were used for descriptions and statistical analyses. RESULTS: There was a statistical difference in the rotation angles between the dominant and non-dominant sides of the sternoclavicular joint when the posture changed from a resting position to a posterior inferior position. During the postural change from a resting position to a horizontal position, the regression coefficient (β) of the humerothoracic joint to the sternoclavicular joint was 0.191, and the β of the humerothoracic joint to the glenohumeral joint was 0.621. During the postural change from the horizontal position to the rear upper position, the β of the humerothoracic joint to the sternoclavicular joint was 0.316, and the β of the humerothoracic joint to the glenohumeral joint was 0.845. During the postural change from the resting position to the rear lower position, the β of the humerothoracic joint to the glenohumeral joint was 0.991. CONCLUSION: The application of the image alignment technique enabled the direct and accurate measurement of the bony structures of the shoulder joint. The helical approach accurately described the scapulohumeral rhythm during 3D motion. There was a scapulohumeral rhythm of the shoulder complex during 3D composite sagittal movement, with different ratios for different joints and postures.