To provide a comprehensive assessment of the condition of the rotator cuff, I believe it is imperative to have an extensive understanding of the composition of the tissues to provide the most reliable interpretation of abnormal findings.
An excellent presentation by one of the world’s leading musculoskeletal radiologists, Professor Martinoli, courtesy of Canon medical on their excellent e-learning platform, Medical Imaging Education (https://medicalimagingacademy.co.uk). Professor Martinoli uncovers a common pitfall which many medical professionals who use ultrasound to investigate the rotator cuff fall foul of.
When assessing the rotator cuff tendons, most literature demonstrates each tendon as a solitary fibrillar complex, extending from a muscle, inserting onto articular cartilage over the humeral head (Image 1).
Image 1: Ultrasound image of the supraspinatus tendon. This is how the normal ultrasound anatomical features are typically represented in literature. Sorced at https://www.fysio.dk/globalassets/documents/fagkongres/2018/praesentationer/ultrasound-imaging-evidence-and-clinical-practice-stuart-wildman.pdf
However, Professor Martiloni highlights that rotator cuff tendons are typically bilayered structures (image 2 and 3) with a superficial fibrillar component which is continuous with the intramuscular aponeurosis which is in fact intimately contiguous with a deeper, non -fibrillar layer composed of the underlying glenohumeral joint capsule!
Image 2: Ultrasound image demonstrating the subscapularis tendon but labelled to demonstrate its actual bilayered composition as described by Professor Martinoli. Sorced at (https://medicalimagingacademy.co.uk).
Image 3: Cadaveric image of the shoulder, demonstrating the subscapularis tendon with its two intimately related layers (tendinous layer and capsular layer). Sorced at (https://medicalimagingacademy.co.uk).
The importance of recognising this composition becomes clear when describing rotator cuff tendon tears.
Consider Image 4 below, an articular sided rotator cuff tear would actually represent damage to the capsular layer (red stars) rather than to the rotator cuff tendon fibres (yellow arrows).
Image 4: Ultrasound image of the subscapularis tendon demonstrating the fibrillar layer extending from the intramuscular aponeurosis (yellow arrows) with the deep capsular layer beneath it (red stars). Sorced at (https://medicalimagingacademy.co.uk).
Therefore, a tear through the articular component likely represents a capsular break and could affect the stability of the shoulder.
Food for thought!
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