[Role of the subacromial space on development of the impingement syndrome. II].

Twenty-five patients with suspected impingement syndrome on the basis of clinical examination were evaluated by magnetic resonance imaging (MRI). In paracoronal and parasagittal planes, different measurements of bony structures of the subacromial space and of the glenoid joint were performed, as in the anatomical study reported in the companion paper. A healthy, age-and sex-matched group of 25 persons underwent the same MRI-procedure and the results were compared with those in the patients. Ruptures of the rotator cuff were excluded by means of standard X-rays, physical examination, and ultrasound. The comparison revealed a highly significant difference between the sizes of the subacromial space. Healthy persons had a space that was larger by more than one third than that of the patients. Other parameters did not differ significantly between the two groups. In a further part of the study the insertion zone of the coracoacromial ligament into the undersurface of the acromion was histologically studied in 24 autopsy specimens. Different staining techniques were used to find out whether microscopic changes occur during different stages of life. Cartilage without bone formation of the acromion was found in children. In adult specimens bony projections of the undersurface of the acromion and thickening of the surrounding fibrocartilage were found, but there was no correlation between ageing and these changes. However, in patients suffering from impingement syndrome the subacromial space is reduced. Acromioplasty enlarges the space by resection of the anterior part of the acromion. Bony spurs on the acromion and a thickening of the fibrocartilaginous layer are not degenerative changes, but they are caused by increased tensile strength of the coracoacromial ligament and are not influenced by age.