腱板断裂の MRI 評価における至適上腕骨回旋肢位

概要

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The optimal position of the humerus when evaluating rotator cuff tears on MRI has yet to be determined.Obtaining a reproducible MR view without individual differences is important but it is sometimes difficult because the inclination of the scapulars are different. We defined the ideal position of the humerus during MRI as follows: 1. Supraspinatus muscle runs straight and is parallel to the scapular plane. The center of the insertion of the supraspinatus tendon was nearly at the border between the superior and inferior facets (S/M border). We rotated the humerus so that the scapular plane was parallel to the S/M line. The S/M angle was defined as the angle between two lines drawn from the center of the humeral head to S/M border and to the bicipital groove. We defined θ as the angle between the scapular plane and the horizontal plane, and β as the angle made by the line drawn from the center to the bicipital groove and the axis of the flexed forearm. The internal rotation angle of the humerus was caluculated as θ + S/M angle+β - 90. Each facet on MR view was investigated. The S/M angle of 50 shoulders converged at 45.4°. θ of 140 shoulders varied. β was 15.2°. The internal rotation angle was expressed as θ - 30, mean 15°. Each facet was easy to evaluate. Rotating the humerus so that the scapular plane ran at S/M border 45°to the bicipital groove produces high quality images.