Shoulder pain secondary to biceps tendon pathology can be quite severe, causing significant disability. Often the exact etiology of the pain is not clear, as the pathogenesis of biceps ten-donopathy is intimately related to existence of other shoulder disorders. Yamaguchi and Bendra10 classified three major groups of pathologic processes in order to help describe and manage biceps disorders: inflammatory, instability, and traumatic. This classification system was designed to characterize the pathologic process present in the biceps tendon, taking into account that overlapping conditions may exist.
Primary bicipital tendonitis, where there is isolated inflammation of the long head of the biceps with no identifiable inciting cause, is rare. In younger athletes, biceps inflammation is usually caused by repeated microtrauma from overuse activities. The development of subacromial impingement is a more common scenario, which can be potentiated by weak periscapu-lar musculature that fatigues with repetitive use. Rotator cuff muscle fatigue results in an elevation of the humeral head further potentiating the impingement. In older patients, degenerative changes of the biceps are frequently associated with impingement and rotator cuff disease. Many times the cause of biceps inflammation is multifactorial.
The long head of the biceps is surrounded by a synovial extension of the glenohumeral joint, and the development of an inflammatory process can be directly related to the structures in proximity. Inflammatory tenosynovitis almost always occurs with concomitant rotator cuff disease as the biceps is subject to the same mechanical wear from the undersurface of the acromion. Neer's11 opinion was that biceps tendonitis was intimately associated with subacromial impingement, and he noted that biceps tendonopathy rarely occurs without a tear of the supraspinatus tendon. With associated tears of the supraspina-tus tendon, the biceps can subluxate medially over the lesser tuberosity. In an autopsy study of 77 cadavers, Petersson12 noted that medial displacement of the tendon was always found in connection with full-thickness supraspinatus tendon ruptures.
In the acute painful stage of biceps tendonitis, inflammation is usually found initially along the tendon in the bicipital groove. This can be easily visualized arthroscopically by using a probe to pull the tendon back into the glenohumeral joint (Fig. 24-1). The biceps tendon can appear swollen, partially frayed, or syn-ovitic. Later on in the course of disease, the tendon can further degenerate and become adherent to the surrounding soft tissue. Microscopic changes include atrophy of collagen fibers, fibrinoid necrosis, and fibrocyte proliferation.13 In the prerupture stage, the tendon can appear either hypertrophic or atrophic and have multiple fissures. In cases of spontaneous rupture, symptoms will often completely resolve.
As the biceps travels from the supraglenoid tubercle to the intertubercular groove, it turns and angles 35 degrees anteriorly. Any damage to the soft-tissue restraints in the rotator interval can cause medial subluxation and even dislocation of the biceps tendon. Patients with this condition usually present with pain and tenderness over the bicipital groove, and a reproducible pop during rotation of the humeral head. When the shoulder is in abduction and external rotation, the biceps is forced medially. During internal rotation, the biceps is forced laterally in the bicipital groove.14 Although this entity has been reported in younger athletes who participate in throwing sports, the cause is not well defined.15 Fixed subluxation of the biceps tendon occurs with complete loss of soft-tissue constraints and is often seen in patients with a disrupted rotator interval or degenerative rotator cuff tears.16 Frank dislocation is almost always associated with a complete tear of the subscapularis tendon or a complete rotator cuff tear involving the rotator interval. The position of the dislocated tendon will usually be evident on magnetic resonance imaging.
Traumatic rupture of the biceps tendon requires a high-energy force, and this is uncommon with no history of biceps tendonitis and degeneration. The mechanism can be a powerful deceleration of the forearm while throwing or in forced supination. Full-thickness tears can be less symptomatic than partial tears. As the biceps originates from the glenoid labrum and the supraglenoid tubercle, many biceps tears are intimately associated with SLAP lesions, as described by Snyder et al.17 In 140 cases of injuries to the superior labrum, the most common cause was a fall or direct blow to the shoulder.18
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