Diagnosing Shoulder Problems with MRI

Magnetic Resonance Imaging (MRI) is a useful tool when diagnosing some, but not all, shoulder problems. In this review article, the preoperative use of MRI for the shoulder is discussed. MRI scans are most helpful when trying to detect rotator cuff tears, impingement syndrome, and shoulder instability.

Anatomy of the rotator cuff is presented, as knowledge of these sites is needed when viewing shoulder MRIs. Healthy tendons don't produce a signal on MRI. Partial-thickness rotator cuff tears (RCTs) are seen as high signal intensity. Full-thickness tears show up as bright fluid throughout the entire tendon.

Shoulder pain caused by impingement from variations in anatomy can be determined from an MRI. Impingements refers to pinching of the soft tissues during shoulder motion.

A flattened surface on the acromion where it should be curved or a hooked undersurface can lead to an impingement syndrome. The acromion is an extension of bone from the shoulder blade that curves around over the shoulder to meet at the collarbone.

The authors also review the anatomy and MRI findings for shoulder instability. Because the shoulder has so much free motion, the muscles and tendons around the joint are important in holding the shoulder in place. Any tears in the joint capsule, ligaments, or cartilage can cause shoulder instability. Instability causes pain but can also lead to dislocation.

The MRI doesn't give the surgeon all the information needed. For example, cartilage tears don't always show up very well. An arthroscopic exam is needed for that. And the surgeon relies on the arthroscopic evaluation to determine what type of surgery is needed. CT scanning is used when details of the bone surfaces are needed.

Reference: 

Robert A. Pedowitz, MD, PhD et al. Effective Use of MRI: Scanning the Shoulder. In The Journal of Musculoskeletal Medicine. December 2006. Vol. 23. No. 12. Pp. 845-848.

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