Physical Examination

Patients who have an acute distal biceps tendon rupture often describe the sensation at the time of injury as tearing, ripping, popping, or electric. The sensation is usually sudden and dramatic. The pain is not excruciating, and it often subsides after several days. Chronic pain in the region of the distal biceps tendon suggests an incomplete or partial tear. Range of motion is normal following an acute distal biceps tendon rupture. Significant swelling and ecchymosis about the medial and anterior elbow regions are common (Fig. 9.1). Ecchymosis is due to the bleeding associated with the rupture from the radial tuberosity. Ecchymosis typically does not appear until 1 or 2 days after injury and begins to resolve within 1 or 2 weeks. It can vary from a small patch that forms in the region of the flexor-pronator origin to an area that extends from the distal third of the medial forearm to the middle portion of the medial upper arm.

Because the biceps muscle is the strongest supinator in the upper extremity, weak supination after tendon rup

FIGURE 9.1. Ecchymosis along the medial aspect of the elbow.

ture is always present. Rupture of the distal biceps tendon makes resisting attempts at passive forearm pronation while the elbow is flexed difficult for even the most muscularly well-developed patient. Weak elbow flexion is not always present. Any of the other muscles that cross the anterior aspect of the elbow can contribute to elbow flexion; therefore, patients who have complete ruptures of the distal biceps tendon may appear to have normal strength when resisted elbow flexion is tested. However, a computerized muscle evaluation, such as Cybex® testing (Cybex II & Human Software, Ronkonkoma, New York), usually demonstrates marked differences in strength between the injured arm and the uninjured arm. The difference is more marked when testing supination than when testing elbow flexion.

Usually, but not always, the biceps brachii muscle belly migrates proximally with a complete distal biceps tendon rupture (Fig. 9.2). When the muscle migrates proximally, a palpable defect exists in the antecubital fossa. In patients who have muscularly well-developed arms, the defect may be difficult to appreciate; however, when the elbow is supported and the arm is relaxed, the difference between the injured and uninjured arm is apparent. The injured arm no longer has the gentle convex curve associated with an intact biceps tendon. The retracted muscle gives a more rounded appearance to the mid-third portion of the arm, creating the so-called Pop-eye arm.

The absence of proximal migration does not rule out the diagnosis of a distal biceps tendon rupture. A tendon may be detached completely from the radial tuberosity, but adherent to either the tendon sheath or the lacertus fibrosis. A tendon also may be ruptured almost completely, but still have enough fibers attached to the radial tuberos-ity to prevent proximal migration. In either case, careful examination reveals thickening about the biceps tendon in the antecubital fossa or softening of the distal portion

FIGURE 9.2. The right arm shows proximal migration of the biceps brachii muscle belly. Note the loss of fullness in the antecubital fossa due to retraction of the biceps tendon and the compensatory contracture of the brachioradialis with resisted elbow flexion.

of the biceps muscle. The thickening may be subtle, but comparing one arm with the other reveals the loss of the normal sharp edge to the medial and lateral aspects of the biceps tendon. The thickening is due to the bleeding and swelling along the tendon sheath. The softening is detected while palpating the distal portion of the biceps muscle while the patient resists elbow flexion. The softening also can be subtle, but comparison with the unin-volved arm assists the examiner in making the diagnosis.

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