Biceps pulley injury

Biceps pulley injuries can be challenging and difficult to diagnose. They can be missed during open and arthroscopic examination, and therefore have sometimes been referred to as a “hidden lesions”.

Anatomy of Biceps Pulley:

The biceps pulley or “sling” is a complex capsuloligamentous structure that helps  to stabilise the long head of the biceps tendon in the bicipital groove. The pulley complex is composed of the superior glenohumeral ligament, the coracohumeral ligament, and the distal attachment of the subscapularis tendon, and is located within the rotator interval between the anterior edge of the supraspinatus tendon and the superior edge of the subscapularis tendon.  

Pathology

Anterior extension of supraspinatus tendon tears may involve the rotator interval capsule. This allows impingement of the biceps tendon between the acromion and coracoacromial ligament, resulting in biceps tendinopathy.

Aetiology

• traumatic: after falling on outstretched arm with full external or internal rotation, as well as backward fall on the hand or elbow
• secondary to rotator cuff tears

Classification

Bennett classification of biceps subluxation instability:

• type 1: injury of the intra-articular subscapularis tendon without involvement of medial head of coracohumeral ligament (CHL)
• type 2: injury of the medial sheath (composed of SGHL-medial CHL ligament complex), without subscapularis involvement
• type 3: injury involving both the medial sheath and subscapularis tendon
• type 4: injury involving the supraspinatus and lateral head of CHL
• type 5: injury involving all structures; intra-articular subscapularis tendon, medial sheath, supraspinatus tendon and lateral CHL

Radiographic features

MRI

SGHL, CHL, and rotator interval capsule structures have intermediate signal filling the rotator interval and surrounding the biceps tendon. These structures may appear thickened when the shoulder is internally rotated as the rotator interval structures will not be taut in this position. Intra-articular fluid (effusion or contrast arthrogaphy) allows better visualisation. 

• identifying the abnormality is not always possible by MRI, however, if there is biceps tendon subluxation or dislocation injury to biceps pulley may be suspected
• injury to superior border of subscapularis tendon has is suspicious for a reflection pulley
• It is often not possible to distinguish between type 1 and type 2 lesions at MRI
• type 3: the biceps tendon can dislocate into the joint
• type 4: the combination of rupture of the LCHL and loss of the normal tension of the MCHL allows the biceps tendon to sublux superficial to the subscapularis tendon and coracohumeral ligament
• type 5: the biceps tendon is free to dislocate anteriorly or into the joint

Treatment and prognosis

Treatment is controversial but mostly biceps tenodesis is usually preferred. There are few published studies on surgical repair.