Anatomy and Function The long biceps tendon arises from the supraglenoid tubercle and partly from the superior glenoid labrum (E). The tendon is intra-articular but extrasynovial, with a surrounding synovial-lined sheath that communicates with the glenohumeral joint and extends into the bicipital groove. As it passes anteriorly and laterally to the bicipital groove, the intra-articular portion of the LHBT is cradled and stabilized by the superior glenohumeral ligament (SGHL) and coracohumeral ligament (CHL), which fuse along the lateral half of the rotator interval with fibers from the subscapularis and supraspinatus to form the biceps pulley (F). The LHBT undergoes a rather abrupt angulation of 30 to 40 degrees as it passes through the pulley and into the bicipital groove1. The intra-articular portion of the long biceps tendon has a flattened and slightly larger cross-sectional contour and transitions to a more rounded and smaller cross-section as it passes into the bicipital groove(G)2. The tendon is smallest in caliber as it exits the bicipital groove3. Within the bicipital groove the deeper, sliding surface of the tendon is avascular and composed of fibrocartilage2. The LHBT is 5-6 mm in diameter and approximately 10 cm in length with the musculotendinous junction found deep to the pectoralis major tendon4. Further distally the long head of the biceps muscle joins with the short head of the biceps muscle to form the biceps muscle belly. Cheng described the arterial supply to LHB tendon as arising from 3 potential sources consisting of branches of the brachial artery entering the tendon at the musculotendinous junction, thoracoacromial artery branches that cross the tendon-bone interface at the glenoid, and a more variable supply via branches of the anterior circumflex humeral artery that travel in a mesotenon to supply the mid-portion of the LHBT5. A relatively consistent zone of hypovascularity is seen 1.2 - 3 cm from the tendon origin5. The tendon of the long head of the biceps is innervated by a network of sensory and sympathetic fibers that are asymmetrically distributed with a higher concentration of innervating fibers at the tendon origin. This distribution is felt to play a role in the pathogenesis of shoulder pain arising from biceps tendon injury.
Posted on: Fri, 14 Nov 2014 19:39:58 +0000
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