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 signal modifications observed in MRI in the supraspinatus tendon apart from any pathology of the shoulder, and due, according to certain authors, to an artefact associated with MRI. Five macroscopically normal supraspinatus tendons were removed from 4 young subjects (14-28 years), 30 min after cardiac arrest, with the authorization of the ethical committee. 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, using a T2-weighted spin-echo sequence, and then studied histologically using 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 signal on the first echo of the sequence. There was a complete correlation 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 exhibited heterogenic images at the first echo, in the second echo the hyposignal was uniform and obvious. The good correlation obtained suggests that modifications of the tendon signal from the supraspinatus m. are not related to an artefact described in MRI, but are linked with premature degeneration of this tendon, probably associated with the severity of the mechanical constraints to which it is subject.