The contours of tuberosities and a pulley mechanism formed by soft tissues maintain the biceps in its groove. There are two pulleys:

There exists a close relation among the LHB, the superiormost intramuscular tendon of the subscapularis muscle, and the SGHL [4] See Fig. 14.4.

The LHB blood supply is from the brachial artery. Three arteries supply blood to the bicipital tendon [17]. Blood supply to the proximal part of LHB is from the anterior circumflex artery, with the branches running along the bicipital groove in both cranial and caudal directions. There is a characteristic vascular pattern on the superficial surface of the tendon within the groove, while the deep “sliding” surface is avascular and composed of fibrocartilage [1]. Labral branches from the suprascapular artery supply the proximal tendon [21].

The distal portion of the tendon receives branches from the deep brachial artery [17] Fig. 14.5.

Clinically, the LHB has been considered a pain generator in the shoulder. According to Alpantaki et al. [2], a rich innervation through a network of sensory sympathetic fibers may explain the bicipital pain. This pattern of innervation is asymmetrical, more concentrated at the biceps origin and less so at the musculotendinous junction. The musculocutaneous nerve is responsible for the motor innervation of the muscle.

Dierickx et al., in a review of 3,000 cases of shoulder arthroscopies, found 57 cases (1.91 %) with variations: the simple vinculum or pulley-like sling, the partial or complete mesotenon between the biceps and the capsule, the completely adherent LHB, the double tendon origin, the reversed-type split tendon, and the complete absence of the LHB. They suggested a classification of 12 variations of the intraarticular portion of the LHB [23].

Four major families, each divided into 1–5 subgroups, were described: Fig. 14.6

Many of these variations, such as the vinculum, the pulley-like sling, and the mesotenon-like adhesions, are mostly of a common kind. They refer to the human embryological evolution of the LHB tendon, which migrates intraarticularly after the fourth month of gestation. This process may apparently stop prematurely, which results in one of the mentioned conditions. These adhesions probably do not cause any pathology [23].

Comparative anatomy has demonstrated the evolutionary movement of the scapula to a more frontal plane with associated torsion of the humeral shaft, thus reducing the action of the LHB at the shoulder [15, 31, 35, 39].

Decreased retroversion of the proximal humerus has led to the groove no longer being centered in the plane of the humeral head, but lying at an angle of approximately 30°. As a consequence, the LHB is forced to bear on the lesser tuberosity at the medial wall of the groove, instead of at its middle. Such a position renders the tendon vulnerable to pathology, since the lesser tuberosity itself acts as a pulley [1].

The function of the biceps tendon has been one of debate. Some suggest that it has no role and is only a vestigial structure, being the “appendix of the shoulder.” Its role in glenohumeral kinematics is controversial. It is important for elbow function, as it is the prime forearm supinator and a significant elbow flexor.

For the shoulder, cadaveric studies have reported that it has a stabilizing effect on the glenohumeral joint in all directions. It is a humeral head depressor and is also an abductor in external rotation.

Despite the possible kinematic effect of the biceps tendon, in vivo studies are yet to establish its stabilizing effect on the shoulder. We know there is minimal functional impact of a biceps tenotomy or tenodesis. Furthermore, EMG studies have demonstrated little or no activation of LHB when the elbow is immobilized. During throwing, the biceps has been shown to function predominantly as an elbow flexor.

In summary, while important for elbow function, the biceps tendon has only a minor contribution to shoulder function. However, if a biceps lesion exists, it is often painful, and often has a significantly detrimental effect on shoulder function.

Ultrasound has proven to be an accurate diagnostic method for LHB tears; however, it is less effective when studying other disorders, such as inflammatory changes or partial tears [52].

Magnetic resonance imaging (MRI) is useful for proximal biceps pathology, both for articular and extraarticular portions. Increased fluid in the synovial sheath is suggestive of tenosynovitis. In sagittal and coronal views, a hyperintense signal under the superior labrum is suggestive of injury of the labrobicipital insertion. The presence of paralabral cysts adjacent to the labrobicipital insertion is also suggestive of injury. The use of gadolinium-enhanced MRI increases diagnostic accuracy; however, experienced radiologists must analyze it so as not to confuse normal anatomic variants such as the sublabral recess with pathological injuries [43]. The diagnostic accuracy of labrobicipital injuries is increased by abduction and external rotation of the arm, as it simulates the peel-back phenomenon, showing the medial labrobicipital complex caudal to the glenoid articular plane Fig. 14.7 [13]. The normal and pathologic anatomy of the biceps reflection pulleys may also be studied by MR arthrography. Oblique sagittal images and axial images are valuable for identifying the individual components of the pulley system [46].

The LHB tendon is one of the most important reference points for orientation during the glenohumeral arthroscopy. The arthroscopic view starts from the posterior viewing portal, where its intraarticular portion and its origin at the supraglenoid tubercle by the labrobicipital union are easily visible. With the arm at the side and in neutral rotation, a better visualization of the intraarticular portion is obtained. It is of major importance to assess the LHB extraarticular or intertubercular portion by applying downward traction with a probe, with an additional 3–5 cm view able to be obtained [26]. The extraarticular biceps portion is a common location for “lipstick synovitis,” delamination, and partial tears. The medial and lateral pulleys complex can be seen with the scope from the posterior portal with the arm in 30° flexion and neutral rotation Figs. 14.8 and 14.9. Associated tears of the subscapularis tendon are common (Fig. 14.8b). Medial displacement of the LHB with internal rotation suggests an anteromedial pulley injury, whereas lateral displacement with external rotation of the arm suggests a posterolateral pulley injury. This is the so-called swinging test [9, 14].