Authors’ Disclosure Statement: The authors report no actual or potential conflict of interest in relation to this article.
Biceps-labrum complex (BLC) disease is a well recognized source of shoulder pain. The BLC can be divided into 3 anatomical zones: inside, junction, and bicipital tunnel. Despite our evolving understanding, diagnosis of BLC pathology through physical examination, standard imaging techniques, and standard diagnostic glenohumeral arthroscopy can be challenging. Selection of the most appropriate surgical technique in refractory cases should take into account decompression of the extra-articular bicipital tunnel. In this article we review the recent literature regarding diagnosis and treatment options for BLC disease.
Pathology of the biceps-labrum complex (BLC) can be an important source of shoulder pain. Discussion of pathoanatomy, imaging, and surgical intervention is facilitated by distinguishing the anatomical zones of the BLC: inside, junction, and bicipital tunnel (extra-articular), parts of which cannot be visualized with standard diagnostic arthroscopy.
The recent literature indicates that bicipital tunnel lesions are common and perhaps overlooked. Systematic reviews suggest improvement in outcomes of BLC operations when the bicipital tunnel is decompressed. Higher-level clinical and basic science studies are needed to fully elucidate the role of the bicipital tunnel, but it is evident that a comprehensive physical examination and an understanding of the limits of advanced imaging are necessary to correctly diagnose and treat BLC-related shoulder pain.
Anatomy of Biceps-Labrum Complex
The long head of the biceps tendon (LHBT) and the glenoid labrum work as an interdependent functional unit, the biceps-labrum complex (BLC). The BLC is divided into 3 distinct anatomical zones: inside, junction, and bicipital tunnel.1,2
Inside
The inside includes the superior labrum and biceps attachment. The LHBT most commonly originates in the superior labrum.3-5 Vangsness and colleagues3 described 4 types of LHBT origins: Type I biceps attaches solely to the posterior labrum, type II predominantly posterior, type III equally to the anterior and posterior labrum, and type IV mostly to the anterior labrum. The LHBT can also originate in the supraglenoid tubercle or the inferior border of the supraspinatus.3,6
Junction
Junction is the intra-articular segment of the LHBT and the biceps pulley. The LHBT traverses the glenohumeral joint en route to the extra-articular bicipital tunnel.2 The LHBT is enveloped in synovium that extends into part of the bicipital tunnel.2 The intra-articular segment of the LHBT is about 25 mm in length7 and has a diameter of 5 mm to 6 mm.8
A cadaveric study found that the average length of the LHBT that can be arthroscopically visualized at rest is 35.6 mm, or only 40% of the total length of the LHBT with respect to the proximal margin of the pectoralis major tendon.1 When the LHBT was pulled into the joint, more tendon (another 14 mm) was visualized.1 Therefore, diagnostic arthroscopy of the glenohumeral joint visualizes about 50% of the LHBT.9The morphology of the LHBT varies by location. The intra-articular portion of the LHBT is wide and flat, whereas the extra-articular portion is round.8 The tendon becomes smoother and more avascular as it exits the joint to promote gliding within its sheath in the bicipital groove.10 The proximal LHBT receives its vascular supply from superior labrum tributaries, and distally the LHBT is supplied by ascending branches of the anterior humeral circumflex artery.4 There is a hypovascular zone, created by this dual blood supply, about 12 mm to 30 mm from the LHBT origin, predisposing the tendon to rupture or fray in this region.11The LHBT makes a 30° turn into the biceps pulley system as it exits the glenohumeral joint. The fibrous pulley system that stabilizes the LHBT in this region has contributions from the coracohumeral ligament, the superior glenohumeral ligament, and the supraspinatus tendon.12-14
The floor of the pulley consists of the superior glenohumeral ligament with reinforcing fibers from the superior border of the subscapularis tendon.15 The roof consists of the coracohumeral ligament fibers with supraspinatus fibers contributing posteriorly (Figure 1).12
Bicipital Tunnel
The bicipital tunnel, the third portion of the BLC, remains largely hidden from standard diagnostic glenohumeral arthroscopy. The bicipital tunnel is an extra-articular, closed space that constrains the LHBT from the articular margin through the subpectoral region.2
The bicipital tunnel itself can be divided into 3 zones (Figure 2).2
Zone 1 is the traditional bicipital groove or “bony groove” that extends from the articular margin to the distal margin of the subscapularis tendon. The floor consists of a deep osseous groove covered by a continuation of subscapularis tendon fibers and periosteum.2Zone 2, “no man’s land,” extends from the distal margin of the subscapularis tendon to the proximal margin of the pectoralis major (PMPM). The LHBT in this zone cannot be visualized during a pull test at arthroscopy, yet lesions commonly occur here.1 Zones 1 and 2 have a similar histology and contain synovium.2Zone 3 is the subpectoral region distal to the PMPM. Fibers of the latissimus dorsi form the flat floor of zone 3, and the pectoralis major inserts lateral to the LHBT on the humerus in this zone. The synovium encapsulating the LHBT in zones 1 and 2 rarely extends past the PMPM. Taylor and colleagues2 found a higher percentage of unoccupied tunnel space in zone 3 than in zones 1 and 2, which results in a “functional bottleneck” between zones 2 and 3 represented by the PMPM.
