Clinical Anatomy

The biceps brachii is a long, spindle-shaped muscle located in the anterior compartment of the arm and arising by the short and long heads. The two heads merge at the level of the deltoid tuberosity to form a single muscle belly. ^, This muscle belly ends in a flattened tendon, which passes deep in the antecubital fossa to insert into the bicipital tuberosity on the proximal radius. The distal biceps tendon inserts on the ulnar aspect of the tuberosity as a ribbon-shaped insertion footprint. Anatomic descriptions show that the long head of the distal tendon inserts onto the proximal aspect of the bicipital tuberosity, whereas the short head of the distal tendon inserts onto the distal aspect of the tuberosity. ^, On average, the biceps tendon insertion starts 23 mm distal to the articular margin of the radial head. A bursa interposes between the distal biceps tendon and the front part of the tuberosity. At the junction of the musculotendinous unit and the distal biceps tendon, the lacertus fibrosus, or bicipital aponeurosis, arises from the medial side of the muscle belly and passes obliquely in an ulnar direction, merging with the fascia covering the proximal flexor mass of the forearm.

Knowledge of the anatomy of the antecubital fossa is essential to the management of distal biceps tendon injuries. The antecubital fossa is the triangular area that is formed between the pronator teres medially and the brachioradialis laterally. The floor of the fossa is formed by the brachialis and by the supinator laterally. Direction should be specified for anatomic orientation. It contains the biceps tendon, brachial artery, and median nerve, from lateral to medial. The brachial artery usually bifurcates at the apex of the antecubital fossa into the radial and ulnar arteries. Close to its origin, the radial artery gives off the recurrent radial artery, which traverses laterally and proximally across the antecubital fossa.

The biceps receives innervation via the musculocutaneous nerve (C5, C6) from the lateral cord of the brachial plexus. Its terminal branch, the lateral antebrachial cutaneous nerve, descends lateral to the biceps tendon into the superficial fascia, and it is vulnerable to iatrogenic injury. The radial nerve pierces the lateral intermuscular septum and courses between the brachialis and brachioradialis to the front of the lateral epicondyle, where it divides into a superficial branch and a deep branch. The superficial branch continues into the forearm beneath the brachioradialis and lateral to the radial artery. The deep branch (posterior interosseous nerve) courses around the lateral neck of the radius and enters between the two planes of fibers of the supinator, where it can be at risk for injury during surgery.

Biomechanics

The biceps brachii is the most powerful supinator of the forearm and contributes to elbow flexion in conjunction with the brachialis muscle. It was reported that the short head, inserted distal to the radial tuberosity, is a more powerful flexor of the elbow, whereas the tendon of the long head, inserted on the tuberosity further from the axis of rotation of the forearm, is a stronger supinator. These functions of the biceps are influenced by the position of the forearm. It is well known that the biceps muscle becomes less active on the prone forearm. The flexor function is augmented when the forearm is in a supinated position, and the biceps becomes the primary supinator of the forearm with progressive flexion of the elbow at 90 degrees.

Demographics and Pathophysiology

Distal biceps tendon rupture was considered a rare injury; only 65 cases were reported before 1941. However, Safran and Graham reported recently an incidence of 1.2 ruptures per 100,000 persons per year. The rupture typically occurs in the dominant extremity of active men between the fourth and sixth decades of life; however, recent research showed that those of any age and of either sex can be affected. There are a few case reports in the literature of partial or complete distal biceps ruptures in women. It has been proposed that the extra strength in males, secondary to the larger cross-sectional area of the biceps, may explain the sex difference in rates of biceps rupture. This cross-sectional sex difference often is particularly evident in the biceps musculature when male and female cohorts are compared.

Acquaviva reported that distal biceps tendon ruptures generally occur as a result of excessive eccentric tension. During a single traumatic event, a sudden extension force is applied to a flexed, supinated forearm, resulting in rupture of the distal biceps. Although the rupture itself is an acute event, a variety of degenerative, hypovascular, and mechanical factors contribute to or even finally cause the tendon tear. Seiler et al. described the interplay of mechanical impingement on the biceps tendon during forearm rotation and hypovascularity as a potential cause. They identified three vascular zones in the distal biceps tendon and reported that a hypovascular zone averaging 2.14 cm was evident between the proximal and distal zones. Also, the same group found that the cross-sectional area through the proximal radioulnar joint at the radial tuberosity decreased almost 50% from full supination to full pronation. However, mechanical failure of the distal biceps tendon at its insertion may be multifactorial. Eames et al. reported that increased tension of the lacertus fibrosus during strong forearm rotation may contribute to mechanical impingement. Other reports suggest that a prominent edge of the bicipital tuberosity erodes the tendon during pronation, rendering it vulnerable to rupture when exposed to high forces. This may be analogous to subacromial impingement and rotator cuff tears.

Finally, abuse of anabolic steroids and nicotine has been discussed in the literature as being possibly related to distal biceps degeneration and rupture. It was reported that there is a 7.5 times higher risk of complete distal biceps rupture in smokers compared with nonsmokers.

Evaluation

Clinical Examination

Patients with complete distal biceps tendon tears usually report an acute event in which an unexpected large load was applied to the flexed arm; others report that they attempted to prevent a fall. This is usually associated with a sudden “pop,” or giving way, followed by pain and weakness in the upper extremity. The initial pain typically subsides in a few hours, and is followed by a dull ache that may last for weeks to months. In the acute phase, there is usually swelling and ecchymosis in the antecubital fossa, extending both distally and proximally. A defect in the antecubital fossa can be palpated, and the biceps muscle belly can be seen retracting proximally with active elbow flexion. If the bicipital aponeurosis is intact, the deformity is not as marked.

Establishing the diagnosis in cases of a partial rupture or subacute or chronic injury may pose a clinical challenge. In cases of partial distal biceps rupture, pain to palpation in the antecubital fossa with resisted supination is the most common finding ( Fig. 84-1 ). Active flexion and supination strength are usually limited by pain. Patients with chronic distal biceps rupture usually present late after a discrete traumatic event with dull pain and weakness in elbow flexion and forearm supination. Asymmetry in the contour of the muscle and dysesthesias in the lateral antebrachial cutaneous nerve distribution are also noted.

Marked pain to palpation into the antecubital fossa with resisted supination is the most common finding in cases of partial distal biceps rupture.

The “biceps squeeze” test has been recently described; to perform this test, the examiner squeezes the biceps muscle belly and looks for forearm supination. Also, the “hook” test might be a valuable test for diagnosing distal biceps tendon avulsions, whether acute or chronic. Its specificity and sensitivity were reported to be very high (both 100%).

Classification

Distal biceps tendon ruptures can be classified as partial or complete. Partial ruptures are often precipitated by minor trauma or may not even be associated with a traumatic event. The latter situation suggests pre-existing degeneration in the tendon. Ramsey further subdivided partial ruptures into insertional (to bone) and intrasubstance (tendon elongation), as seen on MRI.

Complete ruptures are categorized into acute and chronic, based on the interval between injury and diagnosis. Ruptures occurring within 4 weeks are considered acute; injuries presenting after 4 weeks are classified as chronic, and are further subdivided based on the integrity of the lacertus fibrosus. In chronic ruptures, direct reattachment of the biceps may be difficult, if not impossible, in cases of a torn lacertus with proximal retraction of the biceps tendon. The value of defining the chronicity of the rupture and the integrity of the lacertus fibrosus lies in its usefulness in predicting the ease of repair and the anticipated outcome.

Surgical Indications

In the past, nonoperative management of distal biceps tendon ruptures was typical. Nevertheless, it was found that conservative treatment of distal biceps tears leads to an appreciable decrease in strength and endurance in flexion and supination. Nonoperative treatment showed a 40% loss of supination strength and an average 30% loss of flexion strength. Pearl et al. reported that, in the same patient with bilateral rupture, the unrepaired biceps tendon showed 48% less supination strength and 39% less flexion strength than the repaired side.

Acute surgical repair with anatomic reinsertion of the ruptured tendon to the bicipital tuberosity is currently favored in active patients of all ages. Candidates for nonoperative management include elderly low-demand patients, those in whom surgery is contraindicated because of other medical reasons, and those who are unable to follow the strict postoperative rehabilitation program.

In chronic injuries, anatomic reattachment, with or without autograft or allograft, should be attempted. Some surgeons prefer nonanatomic attachment of the biceps tendon to the brachialis muscle to avoid complications associated with deep surgical dissection and the use of the graft; however, this procedure does not restore supination. In this situation, the significant loss of supination strength may be unacceptable for patients with high functional requirements in supination, such as manual workers and athletes, and must be discussed before surgery.

Partial distal biceps tendon ruptures are initially treated conservatively with nonsteroidal anti-inflammatory drugs, orthosis, and physiotherapy. Some physicians recommend local corticosteroid injections. Surgical treatment is reserved for refractory cases.

Surgical Treatment

Complete Ruptures

The goal of any surgical procedure to repair distal biceps tendon rupture should be restoration of the preinjury anatomy and function as closely as possible; thus, early anatomic repair is recommended. Single-incision and two-incision techniques, with various modifications, have been extensively described, each having its advantages and drawbacks. Controversy remains over which approach is superior.

The two-incision technique was first described by Boyd and Anderson in an effort to limit surgical dissection and prevent neurologic injury. This technique involves a small anterior incision and a second posterolateral incision. Their technique, however, was associated with an increased incidence of proximal radioulnar synostosis. Failla et al. claimed that the development of synostosis was related to proximal interosseous membrane damage and stimulation of the ulnar periosteum as a result of subperiosteal exposure of the ulna. They recommended a modified two-incision technique using a limited muscle-splitting approach through the extensor muscle mass; thus, subperiosteal exposure of the ulna is avoided. They also recommended copious wound irrigation to remove bone dust produced from the use of a burr to create a trough in the radial tuberosity. Although this modified approach decreases the risk of radioulnar synostosis and heterotopic ossification, the chance of synostosis has not been eliminated.

Historically, anatomic repair was performed through an extensile single anterior approach with sutures to bone, with an increased incidence of injury to the radial and posterior interosseous nerves, leading to the two-incision technique originally described by Boyd and Anderson. With the advent of newer fixation devices, such as bone suture anchors, EndoButton (Acufex, Smith & Nephew, Andover, MA), and interference Bio-tenodesis screws (Arthrex, Naples, FL), a single-incision anterior approach without extensive dissection of the proximal radius has become increasingly more popular. This limited single anterior exposure theoretically diminishes the risk of neurologic injury and reduces the risk of radioulnar synostosis and heterotopic ossification associated with a dorsal incision. Bone quality must be considered because many of the newer-generation suture anchors require and depend on anterior cortical bone of the bicipital tuberosity for fixation. One of the criticisms of this technique has been nonanatomic reinsertion of the ruptured biceps tendon. If the biceps tendon is not repaired to its anatomic position and is merely inserted into the center of the bicipital tuberosity, the power of supination may never be restored to preinjury levels. Therefore, the bony and insertional anatomy of the biceps tendon and bicipital tuberosity becomes important to reestablish the anatomic footprint during repair.

Author’s Preferred Technique

The patient is placed supine on the operating table, with the affected arm extended on an arm board. A single, modified, anterior Henry incision, centered over the antecubital fossa, is used for the procedure. The lateral antebrachial cutaneous nerve is identified and retracted laterally. The deep fascia is incised, and the distal biceps tendon is identified. If the lacertus fibrosus is intact, the tendon will remain in the tendon sheath. If the lacertus fibrosus is ruptured, the tendon will retract proximally into the anterior compartment of the arm. In chronic cases, the tendon may be enclosed in a cocoon of connective tissue that might give the impression of tendon continuity to the bicipital tuberosity. The tendon sheath is incised longitudinally, the tendon is retrieved and adequately debrided.

The arm is placed in the supinated position, and the interval between the brachioradialis and pronator teres is identified. The brachioradialis is retracted laterally, and the pronator teres is retracted medially. The radial recurrent vessels are ligated to facilitate retraction, which allows safe distal exposure of the bicipital tuberosity. The radial attachment of the supinator is not released. The radial nerve and posterior interosseous nerve are not exposed; instead, they are protected by gentle retraction and, most importantly, by keeping the forearm supinated at all times. Care should be taken to avoid rigorous retraction of the supinator because this will damage the posterior interosseous nerve.

The bicipital tuberosity is exposed and cleared of soft tissue, including residual tendon stump, with a small periosteal elevator.

Two Mitek GII anchors (DePuy Mitek, Norwood, MA), loaded with No. 2 nonabsorbable sutures, are placed in parallel into the bicipital tuberosity under direct visualization. The anchors are centered in the tuberosity, approximately 1 cm apart. The two sutures attached to the anchors are independently passed trough the distal 3 cm of the tendon with a sliding Kessler stitch and then tied through the biceps footprint ( Fig. 84-2 ). The elbow is maintained in full supination and approximately 60 degrees of elbow flexion during suture tying. Routine closure of the wound is then completed. The arm is placed in a well-padded posterior splint with the elbow in 90 degrees of flexion and the forearm in 20 degrees of supination.

A, Schematic illustration of the modified Kessler sliding stitch used to secure the distal biceps tendon to the bicipital tuberosity. The two sutures attached to the anchors are independently passed trough the distal 3 cm of the tendon using a single-incision approach.

(Adapted with permission from Vardakas DG, Musgrave DS, Varitimidis SE, et al. Partial rupture of the distal biceps tendon. J Shoulder Elbow Surg. 2001;10:377-379.)

B, Intraoperative image of the repaired distal biceps tendon into its anatomic position. In this case of acute complete distal biceps rupture, the lacertus fibrosus was disrupted ( arrowheads ).

Chronic Ruptures

Chronic distal biceps ruptures, presenting 4 to 6 weeks after the original injury, pose the additional problem of muscle retraction, distal tendon shortening, and adhesion formation. Chronic ruptures are more difficult to repair than acute ruptures, and the results of late reconstruction are considered inferior and less predictable. In such cases, the surgeon has three options: attempt to mobilize the biceps, perform nonanatomic repair of the distal biceps to the brachialis muscle, and perform distal biceps tendon reconstruction.

Distal biceps mobilization can be achieved by sectioning the lacertus fibrosus (if it is intact), releasing adhesions, releasing the tourniquet, performing relaxing incisions to the epimysium, and applying traction to the distal biceps stump for several minutes. These measures, although helpful, are seldom effective. Even though tenodesis of the retracted tendon to the distal brachialis muscle may increase elbow flexion strength, it does not improve supination strength.

Frequently, suitable graft material is needed for late reconstruction of retracted chronic tears. Autograft options that have been reported include fascia lata, semitendinosus, and flexor carpi radialis. Achilles tendon allograft has also been advocated and can be used if the patient wishes to avoid donor site morbidity. Late reconstruction through a single anterior approach using Achilles tendon allograft is our preferred technique. Although this technique is a demanding procedure and involves a prolonged rehabilitation period, it is an excellent alternative for patients with high functional demands in pronosupination. Although no significant complications were encountered in our series, the possibility of infection and remote disease transmission from the allograft must be considered and discussed with the patient before the procedure.

Partial Ruptures

Partial distal biceps tendon ruptures, confirmed by MRI, that do not respond to conservative treatment are best managed surgically. Surgical excision of degenerative tendon, through either a single- or two-incision technique, debridement of the frayed tendon end, and anatomic reinsertion to the radial tuberosity are recommended.

From our series, we described seven patients who underwent surgical debridement and reattachment of the biceps tendon using a single-incision technique with suture anchors. Intraoperatively, in all cases, the tendon had significant degeneration and softening at the insertion site, but was in partial continuity with the radial tuberosity. The affected portion of the tendon varied from 60% to 90% of the tendon diameter. Approximately 1 cm of the degenerated portion of the tendon was excised to normal tendon substance. Postoperatively, there was a significant decrease in pain, and flexion and supination strength were almost equivalent to those in the noninjured arm. Recently, Dellaero and Mallon, using the same technique (a single incision via suture anchors) reported successful outcomes in all patients.

Postoperative Regimen

After surgery, regardless of the repair technique, the arm is immobilized with the elbow in 90 degrees of flexion and the forearm in 20 degrees of supination. A dynamic, hinged extension block brace is applied at the first postoperative visit, approximately 7 to 10 days postoperatively, in 45 degrees of extension. This dynamic brace uses elastic bands to allow active assisted elbow flexion. The brace is adjusted weekly to allow more extension. It is kept in place to protect the repair for 6 to 8 weeks. Range of motion is advanced to full extension progressively, starting at the third postoperative week. Resisted supination and flexion are not allowed for 12 weeks after surgery. Strengthening exercises are begun at the fourth postoperative month, and unrestricted activities are typically allowed at 4 to 6 months. Chapter 85 provides a detailed discussion of postoperative rehabilitation and orthoses.

Complications

Complications can be stratified according to surgical approach. The main complication of the original single-incision technique is neurologic injury. Lateral antebrachial cutaneous nerve paresthesia and posterior interosseous nerve palsy are the most common nerve injuries. However, the introduction of suture anchors has made an anterior single-incision technique feasible by limiting extensive soft tissue dissection, resulting in minimal morbidity and a low complication rate. McKee et al. reported only three neurologic complications among 57 patients (5.2%) and an overall complication rate of 7.5% (4 of 53) for all patients who were treated via an anterior single-incision technique with suture anchors.

The major complications with the two-incision technique are radioulnar synostosis and heterotopic ossification. Nerve injuries have also been reported.

Early resection of the synostosis, if it develops, is the only treatment to restore a functional range of forearm rotation, but the results are variable. Kelly et al. reported the complications of the two-incision technique using the muscle-splitting modification. In their study of 74 repairs, nerve injuries (which included five sensory nerve paresthesias and one temporary palsy of the posterior interosseous nerve) developed in six patients. Heterotopic ossification developed in four cases; there were no cases of radioulnar synostosis. Conversely, Bisson et al., using the same modified two-incision technique in 45 repairs, reported functional radioulnar synostosis in three patients (7%) and loss of forearm rotation unrelated to heterotopic ossification in two patients. They found an overall complication rate of 27%.

Rerupture is a rare complication with any method of biceps repair, even when, anecdotally, patients do not comply with their postoperative rehabilitation restrictions.