Three-dimensional shoulder kinematics: Upright four-dimensional computed tomography in comparison with an optical three-dimensional motion capture system

Dynamic evaluation of the sternoclavicular and acromioclavicular joints using an upright four-dimensional computed tomography

In the analysis of the shoulder complex, the sequential changes occurring in the sternoclavicular and acromioclavicular joints during active shoulder motion are challenging to track. This study aimed to investigate the in vivo sternoclavicular and acromioclavicular joint motions during active elevation, including the sequential changes in these joint spaces using upright four-dimensional computed tomography (4DCT). Bilateral shoulders of 12 healthy volunteers upright 4DCT were obtained during active elevation similar to a "hands up" motion. The sternoclavicular and acromioclavicular rotation angles, joint distances, and closest points on the clavicle relative to the thorax and scapula were evaluated during 10°-140° of humerothoracic elevation. During humerothoracic elevation, the clavicle elevated, retracted, and rotated posteriorly relative to the thorax, whereas the scapula rotated upwardly, internally, and posteriorly relative to the clavicle. All the sternoclavicular and acromioclavicular joint rotation angles were significantly different at ≥ 30°-50° of humerothoracic elevation compared with 10° of humerothoracic elevation. The mean sternoclavicular and acromioclavicular joint distances were 2.2 ± 1.1 mm and 1.6 ± 0.9 mm, respectively. The closest points were located on the anteroinferior part of the medial and lateral clavicle in the sternoclavicular and acromioclavicular joints, respectively. Significant differences were observed in the acromioclavicular joint distance and anterior/posterior movements of the closest points in the sternoclavicular and acromioclavicular joints compared with 10° of humerothoracic elevation. Our sternoclavicular and acromioclavicular closest point results indicate that the impingement tends to occur at the anteroinferior part of the medial and lateral aspects of the clavicle and may be related to osteoarthritis.

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.

Three-Dimensional Quantitative Evaluation of the Scapular Skin Marker Movements in the Upright Posture

Motion capture systems using skin markers are widely used to evaluate scapular kinematics. However, soft-tissue artifact (STA) is a major limitation, and there is insufficient knowledge of the marker movements from the original locations. This study explores a scapular STA, including marker movements with shoulder elevation using upright computed tomography (CT). Ten healthy males (twenty shoulders in total) had markers attached to scapular bony landmarks and underwent upright CT in the reference and elevated positions. Marker movements were calculated and compared between markers. The bone-based and marker-based scapulothoracic rotation angles were also compared in both positions. The median marker movement distances were 30.4 mm for the acromial angle, 53.1 mm for the root of the scapular spine, and 70.0 mm for the inferior angle. Marker movements were significantly smaller on the superolateral aspect of the scapula, and superior movement was largest in the directional movement. Scapulothoracic rotation angles were significantly smaller in the marker-based rotation angles than in the bone-based rotation angles of the elevated position. We noted that the markers especially did not track the inferior movement of the scapular motion with shoulder elevation, resulting in an underestimation of the marker-based rotation angles.