Proximal Biceps Tendinitis and Tendinopathy

Excerpt

The long head of the biceps (LHB) brachii tendon originates at the supraglenoid tubercle and superior glenoid labrum. Its labral origin is mostly posterior in over half of cases. Inside the joint, the tendon is extrasynovial and passes obliquely, heading toward the bicipital groove. The LHB tendon distally joins the short head of the biceps (SHB) tendon as both transition into their respective muscle bellies in the central third of the upper arm, and after crossing the volar aspect of the elbow, inserts on the radial tuberosity and medial forearm fascia. The latter occurs via the bicipital aponeurosis.

The blood supply to the LHB tendon occurs via the anterior humeral circumflex artery. Two critical areas of avascularity of the LHB tendon have been demonstrated to be located on the deep undersurface of the tendon in the groove, and proximally near its insertion at the superior glenoid.

The bicipital groove is an anatomic landmark that sits between the greater and lesser tuberosities and serves as a critical location of proximal biceps stability. The soft tissue components of the groove create a tendo-ligamentous sling to support the LHB tendon. They include portions of the rotator cuff muscles (subscapularis and supraspinatus), coracohumeral ligament (CHL), and the superior glenohumeral ligament (SGHL).

Biomechanically, the LHBT has a controversial role in the dynamic stability of the shoulder joint. It has been demonstrated, mostly in biomechanical cadaveric-based studies and animal models, that the tendon at least plays a passive stabilizing role in the shoulder. Neer proposed in the 1970s that the LHBTs stabilizing role varied depending on the position of the elbow. Several subsequent studies refuted the theory that the LHBT played any active shoulder stabilizing effect. Jobe and Perry evaluated the activation of the biceps during the throwing motion in athletes. The authors reported the peak muscle stimulation occurred in relation to elbow flexion and forearm deceleration, with very little proximal biceps activity during the earlier phases of throwing.

Thus, in most healthy patient populations, the LHBT plays a negligible role in the dynamic stability of the shoulder. The main function of the biceps muscle is forearm supination and elbow flexion. The biceps also contributes 10% of the total power in shoulder abduction when the arm is in external rotation.