The stabilizing sling for the long head of the biceps tendon in the rotator cuff interval. A histoanatomic study.

A histoanatomic study of the rotator cuff interval was done in 13 cadaveric specimens to investigate the relation of its ligamentous structures to the long head of the biceps tendon, with a special focus on revealing a stabilizing function. After macroscopic evaluation, the lateral half of the rotator cuff interval capsule was cut into three sections: medial, middle, and lateral. These sections were embedded in methacrylate, and then serial sections were made and stained for polarized light microscopy. The superior glenohumeral ligament was seen to form a fold having the macroscopic appearance of a U-shaped anterior suspension sling for the long head of the biceps tendon. Microscopic evaluation revealed an important role of the fasciculus obliquus in the roof of this sling. Fibers of the supraspinatus tendon join the posterosuperior part of the sling. The subscapularis tendon is not involved in this suspensory mechanism. As a result of these observations, we determined that the superior glenohumeral ligament and the fasciculus obliquus are the most important ligamentous reinforcements of a stabilizing sling for the long head of the biceps tendon in the rotator cuff interval. Their histologic appearance indicates they function to protect the long head of the biceps against anterior shearing stress. A lesion of this sling might lead to anterior instability of the biceps tendon.