THE CORACOACROMIAL ARCH - MR EVALUATION AND CORRELATION WITH ROTATOR CUFF PATHOLOGY

The relative prevalence of various acromial shapes, appearance of the coracoacromial ligament and enthesophytes along the inferior aspect of the acromioclavicular joint in patients with and without rotator cuff tears were evaluated. Of 76 patients with clinical instability and im pingement, 31 had a normal rotator cuff and 45 demonstrated a partial or full tear of the supraspinatus tendon at surgery. Results were comp ared with those from magnetic resonance (MR) scans of 57 asymptomatic volunteers. Of the 45 patients with a supraspinatus tear, 38% (17) had a flat acromial undersurface (type I), 40% (18) had a concave acromia l undersurface (type II), 18% (8) had an anteriorly hooked acromion (t ype III), and 4% (2) had an inferiorly convex acromion (type IV). Amon g the 31 patients with a normal rotator cuff at surgery and the 57 asy mptomatic volunteers, the respective prevalences of the type I acromio n were 39% (12) and 44% (25), of type II 48% (15) and 35% (20), type I II 3% (1) and 12% (7), and type IV 10% (3) and 9% (5). Shoulders with surgically proven rotator cuff tears showed a tendential association w ith a type III acromion (8/45) and statistically significant associati ons with a thickened coracoacromial ligament (17/45) and acromioclavic ular enthesophytes (18/45). For the association be tween inferiorly di rected acromioclavicular joint enthesophytes and rotator cuff tears, a ge appears to be a confounding factor. The type IV acromion, newly cla ssified by this study, does not have a recognizable association with r otator cuff tears. Assessment of the osseous-ligamentous coracoacromia l outlet by MR imaging provides useful diagnostic information and may prove helpful to the orthopedic surgeon in patients for whom surgical decompression is contemplated.