The biceps muscle tendon complex may be injured at the musculotendinous junction, in continuity tear of the tendon, and by a complete or partial tear or avulsion from the radial tuberosity. By far the most common injury is that of tendon avulsion, and a complete avulsion is much more common than a partial one. In the past, the rarity of the condition was exemplified by the fact that only 24 cases were reported in a 43-year period from the original surgical description by Johnson¹ in 1897 and Acquaviva² in 1898. By 1956, the world’s literature contained 152 reported cases.³ Currently the injury is well known and the incidence is either increasing or the recognition is more common.^{4,5,6,7,8,9,10,11} Even with the increased reports in the literature, we have encountered only a single instance of involvement in the female in the English literature,¹² and have personally experienced these partial but no complete rupture occurring in a female patient. In addition, over 80% of the reported cases have involved the right dominant upper extremity, usually in a well-developed male,^13,14 averaging about 50 years of age.^15,16,17

In virtually every reported case,^16,17,18 a single traumatic event, often lifting 40 kg or more against resistance with the elbow in about 90 degrees of flexion, has been implicated. This mechanism, along with a tendency for anabolic steroid abuse, accounts for the surprisingly common occurrence in well-conditioned, healthy, competitive weight lifters. Pre-existing degenerative changes in the tendon predispose to the rupture.^19,20 Acute pain in the antecubital fossa is noted immediately. Rarely a patient complains of a second episode of acute pain several days later. Such a history suggests the possibility of an initial partial rupture or of secondary failure of the lacertus fibrosus.^6,21

The histologic pathology is degeneration of the biceps tendon and is consistent with the roentgenographic changes that are often observed on the volar aspect of the radial tuberosity^14,16,22 (Fig. 26-1). During pronation and supination, inflammation and subsequent attenuation of the biceps tendon may occur in concert with a chronic radial tuberosity bursitis.²³ Predisposition to this and other tendon injuries has been associated with hyperparathyroidism,^24,25 those with chronic acidosis,²⁶ and in systemic disease such as lupus erythematosus.²⁷ One interesting study has also implicated a hypovascular zone of tendon near its attachment as a cause or contributing factor to the injury.²⁸

The common symptom of distal biceps tendon rupture is a sudden, sharp, tearing type pain followed by discomfort in the antecubital fossa or in the lower anterior aspect of the brachium. The intense pain usually subsides in several hours, but a dull ache persists for weeks. Activity is possible, but difficult, immediately after the injury. If surgical repair is not performed, however, chronic pain with activity is common.²⁹ Flexion weakness of about 15% is inevitably present but tends to decrease with time.³⁰ Loss of supination strength has been reported as the source of variable, but significant dysfunction averages about 40%.¹⁷ Diminution of grip strength also has been recognized.^4,17,30 Ecchymosis may be present in the antecubital fossa^16,31 and occasionally over the proximal aspect of the ulna.¹³ With elbow flexion, the muscle contracts proximally, and a visible, palpable defect of the distal biceps muscle is obvious. Local tenderness is present in the antecubital fossa. If the defect is not palpable and symptoms are otherwise consistent with the diagnosis, a partial rupture may have occurred. Flexion weakness usually is detectable by routine clinical examination. The loss of strength may be profound,¹⁶ especially supination, immediately after injury. Loss of grip strength is variable in degree but present in most. Some have recommended the routine use of the magnetic resonance imaging (MRI) to make or confirm the diagnosis.⁹ While occasionally helpful (Fig. 26-2),
we have not found this study to be routinely necessary except for concerns of partial rupture.