Supraspinatus Myotendinous Junction Injuries: MRI Findings and Prevalence.

OBJECTIVE: The purpose of this study is to describe the MRI findings and evaluate the prevalence of supraspinatus myotendinous injuries. MATERIALS AND METHODS: Among 1001 consecutive shoulders that underwent either conventional MRI or MR arthrography between January and December 2016, 843 shoulders were included. All MR images were retrospectively analyzed for identification and classification into the appropriate grade of acute or chronic rotator cuff myotendinous injuries. Other MRI findings, such as the presence of rotator cuff tendon insertional tears, and clinical information were also evaluated. RESULTS: At MRI, 0.47% (4/843) of shoulders had supraspinatus myotendinous injuries involving the anterior muscular bundle exclusively. Chronic grade III (n = 2), acute grade III (n = 1), and acute grade II (n = 1) injuries were identified in three men and one woman (mean age, 44 years) with a clinical history of trauma (n = 2) or of progressive shoulder pain (n = 2). A concurrent supraspinatus insertional tendon tear with either partial (n = 1) or full (n = 1) thickness was present in half the cases. Loss of tension of the myotendinous junction in grade III myotendinous junction injuries led to severe atrophy and fatty infiltration of the anterior supraspinatus. CONCLUSION: Supraspinatus myotendinous junction injuries are uncommon at MRI. These lesions invariably involve the anterior bundle of the supraspinatus muscle and may occur with a concomitant insertional tendon tear. High-grade chronic injuries lead to selective atrophy and fatty infiltration of the anterior supraspinatus muscle.