On testing, it has been estimated that patients can experience strength loss of approximately 30% with elbow flexion.1 In contrast, patients with distal biceps tendon ruptures usually complain of pain, swelling, and possibly bruising in the antecubital fossa, as was the case with this patient. Similar to proximal ruptures, the patient may admit to hearing or feeling a “popping” sound if there is an inciting event. The patient may exhibit a “reverse Popeye” deformity, with a bulge in the proximal arm secondary to retraction of the biceps muscle belly proximally.1
There are two tests that can be performed to assist in making the diagnosis—the biceps squeeze test and the hook test.
Biceps Squeeze Test. The first test to assess for distal biceps tendon rupture is the biceps squeeze test, in which the clinician forcefully squeezes the patient’s biceps muscle to observe for forearm flexion/supination. This test is similar in principle to the Thompson test for Achilles tendon rupture. If there is no forearm movement, the injury is suspicious for a complete distal biceps tendon rupture. In one observational study of this test, 21 of 22 patients with a positive biceps squeeze test were found to have a complete distal biceps tendon tear at surgery.3
Hook Test. The second test is the hook test. While the patient actively supinates with the elbow flexed at 900, an intact hook test permits the examiner to “hook” his or her index finger under the intact biceps tendon from the lateral side. The absence of a “hook” means that there is no cord-like structure under which the examiner can hook a finger, indicating distal avulsion.4 In one study comparing the hook test to magnetic resonance imaging (MRI) in 33 patients with this suspected injury, the hook test had 100% sensitivity and specificity, while MRI only demonstrated a 92% sensitivity and 85% specificity.4
The need for diagnostic imaging is based somewhat on the location of the rupture—proximal or distal. Ultrasound has been shown to have a high sensitivity and specificity for identifying normal tendons and complete tears of the long head biceps tendon (ie, proximal). It is not sensitive at identifying proximal partial tears, however. For distal ruptures, ultrasound imaging of the distal biceps tendon is technically difficult and not reliable. For patients with suspected distal biceps tendon ruptures, the EP should consult with orthopedic services prior to ordering an MRI. While MRI is considered the gold standard imaging test, it is neither 100% sensitive nor specific. The bottom line is that the absence of pathologic findings on MRI is not sufficient enough to exclude biceps tendon pathology.5
Treatment and Management
Regarding management, the majority of patients with proximal biceps tendon ruptures tend to do well with conservative management. The exception is for younger, active patients who are less willing to accept the cosmetic deformity, or patients whose occupation makes them unable to tolerate minimal weakness or fatigue cramping (eg, carpenters), in which case referral for a surgical repair (tenodesis) may be appropriate.1 However, multiple systematic reviews examining tenotomy vs tenodesis have not shown any functional improvement, only cosmetic.1,6,7
Distal biceps tendon ruptures are usually treated surgically, since conservative management results in a decrease of 30% to 50% supination strength and 20% flexion strength.1,8 This surgery, however, is not without complications. Approximately 20% of the patients will have a minor complication and 5% will have major complications following surgery on the distal biceps tendon.9 It is preferable to operate on distal ruptures less than 4 weeks from the initial injury; otherwise, these injuries may be more difficult to fix, require a graft, and have less predictable outcomes.1 Nonoperative management should be reserved for the elderly or less active patients with multiple comorbidities, especially if the nondominant arm is involved.10
The PA clearly missed the correct diagnosis on this patient. A more thorough history and focused physical examination would have led to the correct diagnosis sooner, along with earlier surgical repair. It is impossible, however, to know if the outcome would have been any different in this uncommon injury.