Critical analysis of the supraspinatus outlet view: rationale for a standard scapular Y-view

The supraspinatus outlet view has been standardized under fluoroscopic control to become reproducible and comparable; it is the normalized scapular Y-view. Four hundred four healthy shoulders from patients 20 to 80 years old and 63 shoulders with rotator cuff tears underwent x-ray evaluation and were compared. A qualitative study was carried out on the shape of the acromion in relation to Bigliani's types (I, II, III and on the presence or absence of a bony spur on the anterior part of the acromion. Quantitative measurements were determined; the subacromial peak and the spinoacromial angle were assessed for a statistical comparison among the various populations. The acromions of healthy shoulders varied with age (8% type III in patients younger than 60 years, 27% in those older than 60 years), although not significantly. The dominant side and sex of the subjects had no effect. With 29% type III acromions the shoulders with cuff tears differed from those of the healthy shoulders (14% type III). No close correlation was seen between type III acromions and cuff ruptures. The quantitative values of the acromions had no predictive value for cuff rupture. Acromion typology failed to confirm that a type III acromion was responsible for rotator cuff rupture. Spurs are found in increasing incidence with age and in the presence of cuff rupture; whether they are caused by subacromial impingement or by natural aging of the acromion is uncertain.