A new method for measurement of subcoracoid outlet and its relationship to rotator cuff pathology at MR arthrography.

Abstract

Orthopaedic surgical studies have shown that variations in the vertical distance between the tip of the coracoid process and the supra-glenoid tubercle alter the shape of the subcoracoid outlet. Our objective was to measure the vertical distance between the coracoid tip and the supra-glenoid tubercle (CTGT) on MR and to assess whether this showed better correlation with rotator cuff pathology compared with the axial coraco-humeral distance. A retrospective review was performed of 100 consecutive shoulder MR arthrograms. Vertical distance between the coracoid tip and the supraglenoid tubercle was measured in the sagittal oblique plane. Separate assessment was then made of tendon pathology of the subscapularis, supraspinatus and long head of biceps tendons. Axial coraco-humeral distance was then measured. Correlation between tendon abnormalities and the two measurements was then made. Of the 100 cases, 42 had subscapularis tendon lesions, 21 had lesions of the long head of biceps and 53 had supraspinatus tendon lesions. Mean vertical distance from the coracoid tip to supraglenoid tubercle was greater in those with lesions of any of these tendons and was statistically significant for the supraspinatus group (P = 0.005). Reduced axial coraco-humeral distance was also seen in patients with tendinopathy, although with less statistically significant difference (p = 0.059). Our results support orthopaedic studies that have shown that the vertical distance between the coracoid tip and the supraglenoid tubercle increases the incidence and risk of rotator cuff disease by altering the shape of the subcoracoid outlet.