Clinical abnormalities that affect the rotator cuff: A guide for MR interpretation

Rotator cuff disease can be related to a number of factors that include degenerative, vascular, traumatic and mechanical causes. The most common cause of rotator cuff pathology is primary degeneration of the rotator cuff tendons with wear and aging. External and internal impingement, microinstability of the shoulder, trauma, overuse associated with athletic and occupational activities, underlying systemic disorders that weaken the tendon such as diabetes, renal and collagen vascular disease, steroid use and smoking contribute to rotator cuff pathology. Identification of the problem and the origin of the disease can often augmented by the use of magnetic resonance imaging (MRI). It is important to be aware of these causes because they may not be apparent by just identifying the pathology seen on MRI. When finding these lesions on an MRI, the interpreting radiologist and referring clinician should correlate them with symptoms, keeping in mind that there can be a discrepancy between MRI findings and symptoms related to rotator cuff disease. The clinician and the radiologist also need to associate various combinations of abnormalities together and connect them with the etiology. Tendinosis, partial and full thickness tears of the rotator cuff are common, especially as people get older. The supraspinatus tendon is most often involved, followed by the infraspinatus and subscapularis tendons. The teres minor is rarely abnormal, and when it is torn, it is often related to posterior shoulder instability. Rotator cuff defects can be seen in 30% of asymptomatic persons over the age of 60 years (1) and 65% of asymptomatic persons over 70 years of age (2). Tears can be seen in professional throwing athletes without any pain or decrease in performance (3). Many tears do not interfere with normal shoulder activity (4). Yet, there are many symptomatic patients with rotator cuff tears who benefit from therapeutic intervention by arthroscopic or open repair. MRI aids in the assessment of the tendons and muscles for clinical decision-making. It can show which tendons are involved, the type and size of the tear, and if there is retraction or fraying of the tendon ends. Muscle atrophy and fatty infiltration may play a big role in determining if surgery should be attempted. Other findings, such as labral and biceps tendon tears in association with rotator cuff tears are also of crucial interest to the referring clinician.