Anisotropy is the most common cause of interpretation errors in musculoskeletal ultrasound. It occurs when the ultrasound beam is not perpendicular to the tendon. A normal tendon is hyperechoic. In case of anisotropy the tendon becomes anechoic, mimicking a tear.
By changing the angle of the transducer, the anisotropy can be avoided.
In case of a dislocated or luxated long head of the biceps brachii tendon, an intact tendon can be found medial to the bicipital groove. Beware not to mistake the short head of the biceps brachii tendon for the long head. The short head inserts on the coracoid
In case of a full thickness biceps brachii tendon rupture, the proximal part of the tendon can not be identified in the bicipital groove or the rotator cuff interval. Many tears occur where the tendon anchors on the glenoid labrum. Some ruptures occur distal to the tendon anchor, often because of degenerative changes in the tendon. This degeneration or tendinosis can be caused by friction of the tendon in an irregular biciptal groove. In these cases the proximal stump of the tendon retracts and is also absent in the bicipital groove or rotator cuff interval. The distal stump of the tendon also retracts but can be identified distal to the bicipital groove and the stump is in some cases surrounded by fluid.
In case of a partial tendon rupture there is no retraction. A tendon defect can be identified in the tendon. A longitudinal tendon split is also possible and can be caused by friction for example in cases of instability of the tendon.
In older patients treatment of a full thickness biceps brachii tendon rupture is conservative.In younger patients a tenodesis can be performed. The tendon is attached to the humerus at the level of the bicipital groove. In these cases after treatment there is still an empty rotator cuff interval.
When surgical treatment is considered it is important to examine the biceps brachii muscle. In case of an older rupture atrophy occurs of the long head of the biceps brachii muscle. The muscle becomes hyperechoic compared to the short head of biceps brachii muscle. This difference in echogenicity is sometimes called black and white sign. Severe atrophy of the muscle is a contraindication for surgical treatment.
For more examples of pathology of the long head of the biceps brachii tendon visit