Study of the position of calcification in calcific tendinitis of the shoulder

The commonly occurring position of calcification in the calcific tendinitis of the shoulder is said to be the supraspinatus tendon. In the anatomical field, it has been newly discovered that the infraspinatus tendon crosses over the supraspinatus tendon to the superior facet of the greater tuberosity. In this study, we thus attempted to determine the occurring position of calcification on MRI quantitatively. We measured the angle between the bicipital groove and center of calcification, and found it to be 49.5±16.5 degrees. On the other hand, it has been reported that the boundary line between the superior and middle facets is 45.4 degrees externally rotated from the bicipital groove. The protrusion formed at the greater tuberosity at this position imposes mechanical stress on the rotator cuff tendon. As we confirmed that these two angles are very close in this study, it suggests that calcification occurs at the boundary line of the superior and middle facets. Our findings also indicate that calcification often occurs at the infraspinatus tendon. (author)