The Long Head of the Biceps Tendon - Part I

Injuries to the long head of the biceps tendon (LHBT) are reasonably common injuries in throwing athletes and athletes in sports with repetitive hand-above-head positions. These include swimmers, tennis players, cross-fit athletes and gymnasts. Injuries can be as simple as a tendinitis or tenosynovitis, and extend to more traumatic injuries such as full ruptures.

The anatomy of the LHBT and its corresponding structures has been extremely well researched over the last century. You might therefore expect that the function of this structure and its role in shoulder injury is well understood. However, conjecture remains over the exact anatomy and function of this unique anatomical tissue. 

Relevant anatomy

The LHBT is unique as it has both an intra-articular structure that originates inside the glenohumeral joint, becoming extra-synovial as it passes through the anterior rotator interval to enter the bicipital groove. The proximal long head tendon is approximately 9cm long and 5 to 6mm in diameter. The articular portion is flatter and a little larger than the groove portion, which is round and smaller and has an oblique inclination of 30-40 degrees. The tendon then runs through intertubercular groove and courses further down into the bicipital groove, protected by a synovial sheath⁽¹⁾.

In terms of its anatomy and function, LHBT may be likened to the components of a boat:

1. The ‘anchor’ is the proximal attachment of the tendon onto the supraglenoid tubercle and labrum (approximately 50% originate on the tubercle and 50% onto the labrum)⁽²⁾.
2. The ‘pulley’ is the tendon component that runs over the humeral head and is supported by the ligaments that create the ‘biceps reflection pulley system’ (discussed in next section).
3. The ‘gunwale’ is formed by the hard edges of the humerus bone, which form the bicipital groove and houses the tendon and its corresponding sheath as it courses down the humerus to join the biceps muscle.

The ‘biceps reflection pulley system’

Proximal to the bicipital groove, the tendon is stabilised by a ‘biceps reflection pulley system’ (see figure 1). The superior glenohumeral ligament (SGHL) and the coracohumeral ligament (CHL) are the structures that envelope the tendon, and which make up the pulley system - with the SGHL being the more important stabiliser of the LHBT⁽³⁾.

Furthermore, in the bicipital groove, the tendon is stabilised by the transverse humeral ligament, which is formed by fibres from the subscapularis and supraspinatus tendons⁽⁴⁾. However, the transverse humeral ligament is not a significant stabiliser of the ‘biceps pulley’ at the entry of the groove. Doubt has been expressed about the existence of the transverse ligament as a distinct entity, and it may simply be a continuation of the insertion of subscapularis⁽⁴⁾. Furthermore, the pectoralis major tendon also crosses over the tendon in the bicipital groove.