The Analysis Of Spatial Relationship Between The Rotator Cuff And The Subacromial Space In Different Arm Positions

Purpose To explore the distance between acromion and humerous of normal whether or not it changes at different arm abduction. To determine at which position the distance is smallest. To evaluate the relationship between the subacromial space and the rotator cuff.Materials and Methods Fifteen normal volunteers were examined with MRI in six arm positions and coronal thin images were obtained with a spin echo sequence. Using a special positioning device, the arm was placed at 0°, 30°, 60°, 90°, 120°, 150° arm abducion. Of them, 0°～ 90° positions are not rotated, while 120° and 150° positions are slight internal rotated. To evaluate not only the minimal distance both of acromion-humerous(A-H) and clavical-humerous(C-H), but also the spatial relationship between the rotator cuff and the subacromial space.Results The values of A-H and C-H at 60°～150° arm abducion are obviously smaller than those at 0°～30° arm abducion (P<0.01). But the values of A-H and C-H at 60°, 90°, 120°, 150° arm abduction have not statistical difference(P>0.05). The rotator cuff (mainly supraspinatus tendon) just go through between acromion and humerous at 60°-120° arm positions while not at 0°～30°, 150° arm positions. So at 60°～120° arm positions, rotator cuff between the humerous and acromion is often been impinged.Conclusion The closest contact between the supraspinatus tendon and subacromial space occurred at 60°～120° abduction. The findings testified that the patients with impingement syndrome have shoulder pain at 60°～120° abduction in clinic from etiology and pathology. In the future, MRI-based analyses should allow investigating the morphological basis ofthe impingement syndrome, choosing the appropriate therapy and minimizing failure rates of surgery.