Distal biceps tendon injuries typically occur from forced eccentric contraction against a heavy load and are more common in males than females. Most patients who rupture their distal biceps tendon undergo operative repair to minimize strength loss and fatigue. Single-incision and two-incision techniques have been developed in recent decades and achieve satisfactory outcomes. Cortical button and bone tunnel fixation demonstrate superior strength relative to suture anchors and interference screws for acute repairs. Patients who present late or who undergo surgery greater than 4 to 6 weeks from their injury are deemed chronic ruptures and may require autograft or allograft reconstruction.
Key points
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Injury to the distal biceps typically occurs in middle aged, higher demand patients who often require surgical reconstruction to optimize outcome and performance.
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Although MRI is not required to make the diagnosis, it is often performed to confirm a complete rupture and plan surgical management.
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There exists significant controversy regarding the best method of treatment of distal biceps injuries, namely, single-incision versus two-incision surgical techniques.
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Most studies demonstrate good clinical outcomes, regardless of surgical technique chosen.
Introduction
The treatment of distal biceps tendon injuries has evolved considerably over the past several decades. Initially, early reports advocated tenodesis of the biceps to the brachialis because of the high risk of neurovascular injury. With a greater appreciation and understanding of the regional anatomy of the elbow, there has been increased attention on anatomic repair of the biceps tendon. Most orthopedic surgeons advocate for early repair of the distal biceps tendon in young, active patients. There are several studies detailing different methods of fixation, approaches to the radial tuberosity, and patient selection criteria. The following article details the epidemiology, pathoanatomy and biomechanics, and clinical presentation and treatment of distal biceps injuries.
Epidemiology
Distal biceps tendon ruptures account for approximately 3% of biceps brachii injuries. The incidence of these injuries has slowly risen and is estimated at 2.55 per 100,000 population per year. The average age of patients with distal biceps tears is 50 years (range, 18–72; most commonly between ages 40 and 60), and most patients who present with this injury are male. Although the injury can occur in either extremity, it is far more common in the dominant arm and these injuries typically occur in active people. Tobacco use, anabolic steroid use, and elevated body mass index have been associated with an increased risk of distal biceps tendon injuries to variable degrees.
Anatomy and biomechanics
The biceps brachii muscle originates proximally in the upper arm at the level of the deltoid tuberosity. The muscle is contained in the anterior compartment of the arm and is comprised of two heads, the long head and the short head. The long head of the biceps has its’ proximal attachment at the shoulder where it attaches to the superior glenoid tubercle. The short head attaches proximally more medially at the coracoid process of the scapula. After converging in the upper arm, the distal tendon gives rise to the bicipital aponeurosis (lacertus fibrosus), which spreads out in an ulnar direction and blends with the forearm fascia. , With rupture of the distal biceps tendon, is not uncommon for the lacertus fibrosus to remain intact, tethering the biceps tendon in the antecubital fossa and preventing superior migration. Distal to the lacertus fibrosus, the distal biceps tendon then travels deep into the antecubital fossa before attaching to the bicipital (radial) tuberosity of the radius. The distal tendon has been found to have two distinct attachment sites. The tendon of the short head attaches more distal on the tuberosity and is thought to be primarily a flexor of the elbow. The tendon of the long head inserts farther from the axis of rotation of the forearm and acts primarily as a supinator of the elbow. The biceps muscle is innervated by the musculocutaneous nerve, which travels down the arm between the biceps and the brachialis. The most distal continuation of the musculocutaneous nerve is the lateral antebrachial cutaneous nerve, which supplies sensation to the volar and lateral aspect of the forearm. This nerve traverses the antecubital fossa and is easily injured during surgical dissection or retraction at the time of surgery. Vital neurovascular structures (median nerve, radial and ulnar arteries, radial recurrent artery, radial nerve) are in close proximity to the antecubital fossa during surgical approaches to the tendon.
Because of the dual insertion of the distal biceps tendon, the biceps provides power to the elbow in flexion and supination. The biceps contributes more to flexion power as the elbow is supinated. In addition, the biceps contributes maximum supination strength with the elbow at or greater than 90° of flexion. In a prior study by Morrey and colleagues, it was shown that patients who received conservative treatment of distal biceps tendon ruptures demonstrated a 40% loss of supination strength and a 30% loss of flexion strength. Other studies have demonstrated similar findings, with one study demonstrating an 86% decrease in supination endurance in patients treated nonoperatively. Anatomic restoration of the insertion site during repair of the distal biceps tendon is likely critical to achieve optimum power after surgery. In a cadaveric study evaluating one-incision and two-incision techniques, the authors found that the two-incision approach was able to restore the anatomy closer to the native state. This resulted in a 15% increase in supination torque at neutral rotation and 40% more supination power at 45° supination than the nonanatomic, one-incision approach. The optimal method of biceps tendon fixation continues to be hotly debated.
Clinical presentation
History
Most patients who present with distal biceps tendon ruptures will not have had prior pain around the elbow. Often times, the history is one of a forceful, eccentric contraction of the elbow. Patients report their arm being driven or forced into extension while they forcefully contract their elbow to prevent dropping something (ie, carrying a heavy piece of furniture and it is heavier than anticipated). Distal biceps ruptures can occur in competitive weight-lifters during eccentric biceps contractile exercises in addition to football players attempting to make a tackle with one arm as another player is running away, causing an eccentric pattern of contraction to the muscle. Patients often describe a pop or tearing sensation in their arm or forearm. There is often localized swelling around the elbow and antecubital fossa. Days after the injury, patients may notice bruising in the fossa or around the forearm. Once swelling subsides, typically there is a cosmetic deformity of the biceps as it retracts proximally in the upper arm. Patients may report weakness or pain with attempted flexion or supination of the elbow and/or forearm. Once the acute inflammation and swelling subsides, the pain is minimal in some cases, causing a minority of patients to forego prompt medical treatment. Patients who sustain a partial tear to the tendon may report more vague symptoms, such as soreness after activities or pain in the forearm that is poorly localized and deep.
Physical Examination
Patients with distal biceps tendon ruptures may have obvious bruising or swelling around the forearm. There may be an abnormal flexion crease proximal to the elbow where the biceps has retracted. There may also be an obvious cosmetic deformity (commonly referred to as a “Popeye” deformity) ( Fig. 1 ). Palpation of the bicep elicits tenderness at the distal portion of the muscle and the tendon can often be palpated in the forearm or upper arm. If the lacertus fibrosus is intact, the tendon can sometimes be palpated deep to the lacertus, but there may be less of a deformity in these cases. Weakness and pain can often be elicited with resisted forearm flexion and supination. Full range of motion of the elbow is typically the norm for most patients. Patients who present with chronic ruptures (>4 weeks) may no longer have tenderness or overt signs of rupture but likely demonstrate atrophy of the biceps muscle and diminished strength. In cases of complete rupture such tests as the biceps squeeze test or the hook test can further help to make the diagnosis. In the squeeze test, with the forearm in neutral rotation, the examiner squeezes the biceps brachii muscle. If the biceps is intact, the forearm supinates (similar to the Thompson test for Achilles rupture). The hook test is performed by placing the arm at 90° of flexion and the examiner attempts to hook the lateral edge of the biceps tendon with the index finger (pulling from a lateral to a medial direction) ( Fig. 2 ). A positive test elicits a cordlike, intact tendon. An abnormal test (positive rupture) does not elicit a palpable tendon in the antecubital fossa. Comparing the injured extremity with the opposite extremity is helpful in less obvious cases. In patients with a partial tear, direct compression of the radial tuberosity during pronation and supination may elicit tenderness and could help to raise suspicion of a partial tear in patients with an otherwise normal clinical examination.
Imaging
Imaging typically starts with a routine radiographic elbow series (anteroposterior, lateral, oblique views). Most patients have no evidence of fracture or other osseous injury. There may be soft tissue swelling in the antecubital fossa on radiographs and, in rare cases, a bony avulsion off the radial tuberosity. MRI is a useful adjunct to confirm the diagnosis but is not often necessary when the clinical picture is as described previously for acute ruptures ( Figs. 3 and 4 ). Specialized imaging protocols, such as the elbow flexed, shoulder abducted, and forearm supinated view (FABS view), allow for complete imaging of the distal biceps on MRI. MRI is especially helpful in cases of partial tendon injury and in patients who have a body habitus that precludes an accurate clinical assessment. Although ultrasound is not routinely used for diagnosis of distal biceps tendon injuries, it is a useful tool in the hands of experienced ultrasonographers.
