Key points

Anatomy

The biceps brachii is a diarthrodial muscle, which acts as a powerful forearm supinator. The muscle is located in the anterior compartment of the arm and is innervated by the musculocutaneous nerve. As the name implies there are 2 heads of the biceps brachii, short and long. The short head originates from the coracoid tip, whereas the long head originates from the supraglenoid tubercle and/or superior labrum. The distal biceps tendon can be found in the antecubital fossa between the brachioradialis and the pronator teres. The tendon courses distally and inserts onto the radial tuberosity 23 mm distal to the articular cartilage of the radial head. The footprint on the radial tuberosity measures 21 mm by 7 mm and is located on the posterior ulnar surface, with the short head inserting more radial and distal to the proximal and ulnar long head ( Fig. 1 ). A secondary attachment includes the lacertus fibrosis, which attaches medially to the deep fascia of the anterior compartment and may prevent retraction of the ruptured distal biceps tendon.

Cadaver specimen with the short and long head insertions mapped out with red and blue ink. Note that the short head inserts distal to the long head and occupies a larger area.

( From Jarrett CD, Weir DM, Stuffman ES, et al. Anatomic and biomechanical analysis of the short and long head components of the distal biceps tendon. J Shoulder Elbow Surg 2012;21:942–8; with permission.)

Anatomy

The biceps brachii is a diarthrodial muscle, which acts as a powerful forearm supinator. The muscle is located in the anterior compartment of the arm and is innervated by the musculocutaneous nerve. As the name implies there are 2 heads of the biceps brachii, short and long. The short head originates from the coracoid tip, whereas the long head originates from the supraglenoid tubercle and/or superior labrum. The distal biceps tendon can be found in the antecubital fossa between the brachioradialis and the pronator teres. The tendon courses distally and inserts onto the radial tuberosity 23 mm distal to the articular cartilage of the radial head. The footprint on the radial tuberosity measures 21 mm by 7 mm and is located on the posterior ulnar surface, with the short head inserting more radial and distal to the proximal and ulnar long head ( Fig. 1 ). A secondary attachment includes the lacertus fibrosis, which attaches medially to the deep fascia of the anterior compartment and may prevent retraction of the ruptured distal biceps tendon.

Cadaver specimen with the short and long head insertions mapped out with red and blue ink. Note that the short head inserts distal to the long head and occupies a larger area.

( From Jarrett CD, Weir DM, Stuffman ES, et al. Anatomic and biomechanical analysis of the short and long head components of the distal biceps tendon. J Shoulder Elbow Surg 2012;21:942–8; with permission.)

Background

Ruptures of the distal attachment of the biceps brachii are a rare injury with a reported rate of 1.2 per 100,000 patients or 2.55 per 100,000 patient-years. Ruptures typically occur in the dominant arm of men in the fourth or fifth decade of life. Patients report an eccentric extension load on a flexed elbow followed by a pop with pain, swelling, and ecchymosis in the region of the antecubital fossa. Frequently, patients present with anterior arm pain and weakness with elbow flexion and supination and a deformity secondary to retraction of the biceps.

Nonoperative treatment

Nonoperative treatment includes early range of motion and advancement to resistive exercises and functional rehabilitation within 4 weeks of injury. Nonoperative treatment leads to acceptable functional outcomes in sedentary or low-demand patients. However, active patients generally are limited by a decrease in supination strength and endurance of 21% to 55% and 86%, respectively. Elbow flexion strength is also decreased by 8% to 13%, and endurance is decreased by 62% in nonsurgically treated patients. As a result of this decrease in function, surgical repair is commonly recommended for young active patients.

Operative treatment

Current indications for distal biceps repair include full-thickness tears or partial-thickness tears, which have failed conservative treatment in active, healthy, compliant patients who desire full strength and endurance. Nonanatomic and anatomic repairs have been described. Nonanatomic repairs in which the biceps is repaired to the brachialis reconstitutes the contour of the biceps muscle; however, nonanatomic repairs do not restore supination strength or biceps endurance power. Contemporary techniques utilize either 1 or 2 incisions. A variety of fixation devices have been described that facilitate strong repairs.

Before 1961, operative treatment was fraught with complications with a rate of radial nerve injury close to 15%. In 1961, the Boyd-Anderson 2-incision technique was proposed for the anatomic repair of the distal biceps tendon in order to reduce the incidence of radial nerve palsy. This technique used an anterior incision to retrieve and deliver the distal biceps tendon to a posterior incision where the biceps is repaired to the exposed biceps tuberosity. Exposure of the biceps tuberosity posteriorly required subperiosteal elevation of the anconeus, which led to a high rate of heterotopic ossification (HO) and synostosis. Using this technique, Karunakar and colleagues demonstrated that 66% recovered strength and endurance of supination and flexion with no radial nerve palsies.

Although patient satisfaction remained high, the Mayo modification of the 2-incision technique has been described to perform a muscle-splitting approach through the extensors in an attempt to prevent HO and synostosis. Recently, the one-incision technique has been advocated by some surgeons. Proponents of this technique report a decreased rate of HO and synostosis with low rates of posterior interosseous nerve (PIN) injury. Critiques of the one-incision technique include failure to anatomically restore the distal biceps attachment and an increased rate of lateral antebrachial cutaneous nerve (LABC) neuropraxia. Although most surgeons agree that repair in active healthy patients is indicated to restore function, currently there is no consensus on whether the one- or 2-incision technique should be used. Recent studies show no difference in complication rates; however, the anterior-only approach is associated with an increased rate of LABC neuropraxia.

Results

Functional results of the operative treatment of distal biceps ruptures are generally favorable with high patient satisfaction rates (>90%). Most studies report greater than 80% recovery of flexion and supination strength and endurance, with some studies reporting increased strength and endurance when compared with the atraumatic contralateral side. Patients must also be counseled on the cosmetic differences between operative and nonoperative treatment. Nonoperative treatment of a retracted ruptured biceps tendon may lead to a change in contour of the anterior arm. Although the contour may be reestablished with operative treatment, scars on the anterior arm may prove to be unsightly for some patients.

General complications

Overall complication following with repair of the distal biceps tendon vary, with studies reporting ranges between 0% to 50%. The total complication rate is estimated between 15 and 35%. These common complications include neurologic injuries (10%–15%), HO (0%–50%), reruptures (1%–5%), hardware failure (0%–20%), chronic regional pain syndrome (CRPS) (2%), wound problems (2%–30%), stiffness (4%), and weakness (15%–50%), with some more rare complications being reported. Multiple studies have shown no difference in complication rates between 2-incision and one-incision techniques; however, an anterior-only repair is associated with a higher rate of LABC palsy. Several studies support an increased complication rate with the use of suture anchors or transosseous screws when compared with cortical button or transosseous suture repair ; however, a recent study by Banerjee and colleagues suggested a higher complication rate with cortical button repair. Researchers have suggested that repair of the distal biceps tendon has a steep learning curve, suggesting that more experienced surgeons may have a lower complication rate.

Lateral antebrachial cutaneous nerve

The LABC is a continuation of the musculocutaneous nerve from the lateral cord of the brachial plexus and provides sensation to the radial aspect of the forearm. The anterior exposure for repair of the distal biceps often encounters the LABC as it emerges from between the biceps and brachialis and then runs laterally between the biceps and the brachioradialis where it divides into volar and dorsal branches.

Current literature reports a 5% to 57% rate of injury to the LABC. Most injuries to the LABC are transient neurapaxias and typically result in temporary numbness along the lateral aspect of the forearm; however, some may persist for years. In the case of neurotmesis, a painful neuroma may develop and permanent numbness and dysesthesias may result.

To prevent injury to the LABC, the nerve should be identified and protected during the anterior approach, especially in the case of chronic ruptures in which adhesions must be released to allow for additional excursion of the tendon for repair. Proximal retrieval of the biceps tendon may jeopardize the nerve as it passes between the brachialis and biceps muscle bellies. In the case of partial biceps tendon attrition, some researchers advocate a posterior-only approach in order to prevent injury to the anterior structures.

In the event of an injury to the LABC in which the nerve was visualized in continuity, intraoperatively, watchful waiting is generally undertaken. Although rare, an intraoperative laceration of the nerve may require repair to prevent permanent decreased sensation over the radial aspect of the forearm and neuroma formation.

Posterior interosseous nerve

The radial nerve arises from between the brachialis and brachioradialis muscles and gives rise to the PIN and superficial radial sensory nerve. The PIN courses between the deep and superficial heads of the supinator and then lies on the dorsal cortex of the radius proximally, innervating the muscles of the dorsal compartment of the forearm. The terminal branch of the PIN lies in the floor of the fourth dorsal compartment sending sensory branches to the wrist joint.

Injury to the PIN can occur with both the one-incision and 2-incision approach and may occur via errant drill bit placement, entrapment under a cortical button, or dissection along the proximal radius. Injury to the PIN leads to weakness with finger and thumb extension and radial deviation with attempted wrist extension. Historically, repair of the distal biceps tendon was complicated by injury to the PIN in 10% to 15% of patients. More recent literature has suggested that injury to the PIN has decreased to less than 10%, with rates as low as 1%.

Prevention of injury to the PIN is important no matter what technique is used to repair the distal biceps tendon. When using an anterior approach, the arm is supinated to protect the PIN and when passing pins or drilling. Oscillation or tapping of the slotted passing pin is recommended to prevent ensnarement of the posterior soft tissues. The PIN is also at risk during placement of transosseous sutures or a cortical button, which is seated on the posterior-lateral radius. A small posterior-lateral incision can be made to ensure that the PIN is not under the cortical button. Intraoperative fluoroscopy to ensure that the button is seated appropriately on the proximal radius with no soft tissue interposition is recommended. In either case, the cortical button should be deployed just as it exits the posterior cortex, so as to avoid soft tissue entrapment. Multiple cadaveric studies have determined the most dangerous orientation of drill bit use in the proximal forearm is distal and radially directed drilling at the radial tuberosity. This technique put the PIN at the most risk, with drill bits impaling or penetrating within 1 mm of the PIN. Drilling is recommended with the forearm in full supination with the drill directed anterior to posterior in a slightly ulnar direction. Cadaveric studies show the cortical button to be an average of 9.3 mm from the PIN, with the closest being 7 mm when drilled anterior to posterior in full supination.

When performing the posterior portion of the 2-incision approach, pronation of the forearm is important to move the PIN anterior to the surgical field. Although this may help to protect the PIN, it may also lead to compression. Some researchers advocate performing the anterior approach followed by placement of a blunt instrument over and around the ulnar side of the radius. The blunt instrument is advanced through the extensor digitorum communis, and an incision is made over the now subcutaneous instrument on the posterior-lateral aspect of the elbow. When using retractors along the radius, some surgeons discourage the use of a Hohmann retractor over the radial aspect of the proximal radius to avoid injury to the PIN ( Fig. 2 ). No matter what approach and instrumentation is used, if dissection within the supinator is performed, visualization of the PIN is recommended.

Anterior approach to left arm. ( A ) Superficial branch of the radial nerve and the vascular leash of Henry can be seen. ( B ) Leading proximal edge of supinator can be seen. ( C ) PIN (not seen) is protected by a Hohmann retractor.

In the event of an observed, intraoperative injury to the PIN, standard nerve repair principles should be adhered to in order to prevent long-term functional deficits. If embarrassment of the PIN is found on the postoperative examination and the nerve was not visualized intraoperatively, early exploration with release of the offending structures or repair of the lacerated nerve should be considered. If the nerve was visualized in continuity at the end of the procedure with no impingement of hardware, a wait-and-see approach may be used, as a neurapraxic injury is most likely. Electrodiagnostic studies may be performed as early as 3 weeks in order to give a baseline status for the nerve. Exploration and nerve repair or neurolysis should be performed early if there is a lack of evidence of reinnervation on serial neurodiagnostic studies. Waiting beyond 6 months for exploration, neurolysis and/or nerve repair is likely to lead to poor results. In the case of chronic PIN injuries greater than 6 months, tendon transfers are recommended to reestablish finger extension and thumb interphalangeal joint extension.