TENDON OF THE NORMAL SUPRASPINATUS MUSCLE - CORRELATIONS BETWEEN MR-IMAGING AND HISTOLOGY

The aim of this study was to attempt to specify the nature of the sign al modifications observed in MRI in the supraspinatus tendon apart fro m any pathology of the shoulder, and due, according to certain authors , to an artefact associated with MRI. Five macroscopically normal supr aspinatus tendons were removed from 4 young subjects (14-28 years), 30 min after cardiac arrest, with the authorisation of the ethical commi ttee. These tendons were examined by MRI in the frontal oblique plane along the axis of the muscle with a surface coil of 4 cm diameter, usi ng a T2-weighted spin-echo sequence, and then studied histologically u sing the same plane of section, 22 control subjects (18-24 years) were examined by MRI with the same T2-weighted spin-echo sequence. All the tendons examined possessed a dark signal with zones of intermediate s ignal on the first echo of the sequence. There was a complete correlat ion between the MRI appearances of the 5 tendons and their histologic description. Three histologic appearances were described : fibrillary degeneration, fibrous dystrophy, and eosinophil transformation of the tendinous collagen. All the tendons examined in healthy volunteers exh ibited hetereogenic images at the first echo; in the second echo the h yposignal was uniform and obvious. The good correlation obtained sugge sts that modifications of the tendon signal from the supraspinatus m. are not related to an artefact described in MRI, but are linked with p remature degeneration of this tendon, probably associated with the sev erity of the mechanical constraints to which it is subject.