Influence of age on scapulo-thoracic orientation

Background. Scapular activity during shoulder motion is critical for normal shoulder function. With aging, muscle function deteriorates in almost all people, which may lead to shoulder impingement syndrome. Methods. Forty-four normal subjects, 23 men and 21 women aged from 16 to 73 years with a mean age 48, were enrolled in the study. Static antero-posterior radiography at both 0° and 90° of abduction were undertaken and correlation between age and scapular orientations were evaluated by Pearson’s correlation coefficient test. The purpose of this study is to investigate the relationship between aging and scapulo-thoracic orientation. Findings. Significant correlation coefficients were observed between aging and scapular orientations. With the shoulder at 0° abduction, posterior tilt showed significant negative correlation with aging. At 90° abduction, both posterior tilt and upward rotation angle correlated negatively with aging. The correlation was apparent at 90° abduction. Interpretation. The results indicate that shoulder aging closely relates to changes of scapular orientation, which consist of decreases of the posterior tilt at 0° and 90° abduction and the upward rotation angle at 90°. The current study indicated that one of the effects of aging on the shoulder is a decrease of posterior tilt and upward rotation angle as seen in an abducted position; and that these alterations are similar to the scapular kinematics of shoulder impingement syndrome. By taking this concept into consideration, the effects of aging on shoulder kinematics can be appropriately evaluated.