Magnetic resonance in the assessment of critical points of impingement of the shoulder

Impingement syndrome is caused by a conflictual status between rotator cuff, subacromial bursa and anatomic and functional acro-mioclavicular arch. The clinical signs of this syndrome include pain and functional disability in abduction and extrarotation of the shoulder. This study was aimed at verifying Magnetic Resonance Imaging (MRI) capabilities in showing the critical points of impingement and their incidence. Fifty-four cases of impingement syndrome were studied. The best visualization of functional acromioclavicular arch was obtained using a new study technique. All patients had critical points of impingement. In 65% of cases, acromioclavicular arthritis induced impingement on the supraspinatus tendon and in 35% of cases on the muscle. In 46% of the patients, impingement between coracoacromial ligament, partially thickened in 25% of the cases and totally thickened in 75%, and supraspinatus tendon was observed. In 7% of the whole of shoulders, the acromion had an uncinatus shape. MRI, thanks to its multiplanar imaging, allowed the complete evaluation of the articular structures with complex anatomy. The assessment of different types of impingement points can be considered a valuable approach to the therapeutic stage.