MAGNETIC-RESONANCE-IMAGING OF THE SHOULDER IN ABDUCTION

To simulate the painful arm position in subacromial impingement syndro me, magnetic resonance imaging of the shoulder was done with the arms at the sides and at 80 degrees abduction in two groups of patients, Gr oup A had 20 shoulders in 20 patients with subacromial impingement syn drome and Group B had 19 shoulders in 19 patients without impingement syndrome, When arm position was changed from adduction to abduction, a n increase in signal intensity of the rotator cuff tendon was seen mor e often in Group A (45%) than in Group B (26%), Group A shoulders show ed encroachment of the acromion or the acromioclavicular joint to the rotator cuff in 25% of the shoulders with the arms at the sides, and i n 75% with the arms in abduction, Similar findings were observed in on ly 14% and 21% of Group B shoulders in the respective arm positions, A bduction of the arms seemed to cause encroachment of the overlying str ucture, especially of the acromioclavicular joint, to the rotator cuff in patients with subacromial impingement syndrome, even if there were no such findings in the images with the arms at the sides.