ANATOMICAL RELATIONSHIPS AND SCAPULAR ATTACHMENTS OF THE SUPRASPINATUS MUSCLE

Ten anatomical preparations and 15 MRI scans (Magnetic Resonance Imagi ng) performed on healthy subjects were used to define accurately the l ateral attachments and anatomical boundaries of the supraspinatus m. U sing 5 frozen specimens sectioned in the plane corresponding to the sa gittal oblique MRI plane, it was possible to calculate quantitatively the ratio between the bony contours (O) and muscles (M) of the suprasp inous fossa. This ratio was maximal (O/M = 2.4) for the section passin g through the plane which included the coracoid process anteriorly and the spine of the scapula posteriorly (''Y'' section). Five dissection s on unembalmed subjects demonstrated that the postero-lateral origin of supraspinatus m. extended further laterally than classically descri bed. This observation was confirmed in the 15 MRI subjects which showe d that the supraspinatus m. may arise as far laterally as the ''Y'' se ction on MRI in 53% of cases. A quantitative evaluation of atrophy of the supraspinatus m. using MRI is possible with a knowledge of these t wo parameters.