We have been using the supination-pronation test in our clinical practice for 2.5 years. In our experience, opportunities to use the supination-pronation test are very limited and specific. This type of tendon avulsion is rare, and the number of patients who warrant clinical examination using the supination-pronation test is small. We have had 5 positive supination-pronation tests in patients with suspected distal biceps tendon ruptures. To confirm if the supination-pronation test correctly demonstrated a full biceps tendon rupture in these 5 patients, we followed their clinical examination with MRI of the involved arm. Only 4 of the 5 patients were able to obtain MRI. Of these 4, all studies showed complete tearing of the distal biceps tendon from its attachment on the radial tuberosity. All 5 patients were taken into the operating room to confirm the clinical diagnosis and then repair it surgically. Through surgical exploration, we observed a full and complete tear of the distal biceps tendon in all patients, and the tears were repaired successfully. Postoperatively, all patients showed a full recovery with no complications, and all were able to regain full range of motion and strength in the involved arm. All 5 patients were discharged with no complaints.
Although we have not encountered false positive and false negatives using the supination-pronation test in clinical practice, we speculate that there would be a low rate of incidence for these outcomes. There is a possibility of a false-positive test in obese patients in whom the contours of the biceps are difficult to appreciate (although we have not observed this clinically). In these patients, the examiner may not see the migration of the biceps that is occurring. In practice, we have found that, if the contours of the bicep are difficult to appreciate, the test can be performed with the examiner placing his/her hand on the muscle belly during the test to actively feel for movement. This could decrease the risk of a false-positive supination-pronation test. A false negative may occur if the distal biceps tendon is almost completely torn. In this case, enough of the tendon fibers may remain intact to pull the biceps muscle belly distally as the hand is pronated. In our experience, this was not observed but should be noted as a potential risk for a false-negative test.
If the lacertus fibrosus is intact, and the distal biceps tendon is ruptured, the biceps will still change shape as the elbow is flexed and extended but will not change shape with supination and pronation. The biceps brachii muscle attaches distally to the radial tuberosity of the radius; contraction of the muscle pulls the tuberosity anteriorly, rotating the forearm into supination. When the forearm rotates into pronation, the tendon is pulled distally and the muscle lengthens, which causes the contour to be more elongated. Since the lacertus fibrosus attaches to the proximal ulna, it is not involved in forearm supination and pronation. It does, however, assist with elbow flexion.
It is very important to isolate the biceps brachii tendon from the lacertus fibrosus and the brachialis because the examiner may miss a distal tendon rupture by not isolating supination and pronation. The supination-pronation test is a novel clinical test that allows the examiner to isolate the biceps brachii tendon in supination and pronation to evaluate for distal biceps tendon rupture. It has been well established that early anatomic repair of distal biceps tendon rupture is advocated for optimal results in returning flexion and supination strength.3,4,6 Although some patients may choose nonoperative management of complete ruptures, prompt diagnosis of the injury is vital so that the option of surgical management at the time of presentation is not compromised by delay in diagnosis. Clinically, we have found that a delayed diagnosis results in more difficulty performing the surgery, and it may not be possible to obtain enough excursion for the biceps to be reattached with the passage of time. The literature suggests that patients with chronic ruptures (more than 4 weeks) often present with proximal retraction of the biceps muscles and scarring to the brachialis, which can make anatomic repair a difficult challenge.3,7
It is important to note the differences in treatment of proximal versus distal bicep tendon ruptures. Proximally, there are 2 tendon attachments. The tendon of the short head attaches to the coracoid process of the scapula. The tendon of the long head runs into the shoulder joint, attaching intra-articularly to the superior aspect of the glenoid. This tendon is often involved in degeneration concurrently with the adjacent rotator cuff and is vulnerable to rupture. Rupture of this tendon is usually treated nonoperatively. Because proximal rupture nearly always affects only the tendon to the long head, the muscle preserves 1 proximal attachment and continues to function, both as a supinator and as a flexor. Also, this type of rupture tends to occur in more elderly and less active patients who are less adversely affected by the modest loss of function associated with proximal ruptures.