Distal biceps ruptures occur from eccentric loading of a flexed elbow. Patients treated nonoperatively have substantial loss of strength in elbow flexion and forearm supination. Surgical approaches include 1-incision and 2-incision techniques. Advances in surgical technology have facilitated the popularity of single-incision techniques through a small anterior incision. Recently, there is increased focus on the detailed anatomy of the distal biceps insertion and the importance of anatomic repair in restoring forearm supination strength. Excellent outcomes are expected with early repair of the distal biceps, with restoration of strength and endurance to near-normal levels with minimal to no loss of motion.
Key points
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Distal biceps ruptures usually occur with eccentric extension loading of a flexed elbow.
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Surgical approaches include 1-incision or 2-incision techniques, with recent studies showing more anatomic repair and improved supination strength with a 2-incision technique.
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Fixation techniques include bone tunnels, cortical buttons, suture anchors, and biotenodesis screws, with cadaveric studies demonstrating the highest load to failure with the button technique.
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Chronic distal biceps ruptures may require reconstruction with tendon allograft due to proximal retraction, and often, poor tissue quality.
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Complications include elbow stiffness, heterotopic ossification, rerupture, and nerve injury, with transient neurapraxia of the lateral antebrachial cutaneous nerve being the most common.
Introduction
Distal biceps ruptures occur at an incidence of 1.2 per 100,000 persons per year, representing 10% of all biceps injuries. They are most common in the dominant arm of men in their fifth and sixth decades of life. Other risk factors include smoking, anabolic steroid use, and weight-lifting. The mechanism of injury is most commonly forceful eccentric extension of a flexed elbow. Proposed etiologies of distal biceps ruptures include decreased vascularity, impingement of the tendon against the radial tuberosity, and degenerative changes due to radial bursitis. There is a 2-cm hypovascular zone in the distal biceps between the perforators from branches of the posterior interosseous recurrent artery distally and the brachial artery proximally. With forearm rotation from supination to pronation, there is a 50% reduction of the space in the proximal radioulnar joint, with the distal biceps occupying 85% of the space in full forearm pronation.
Introduction
Distal biceps ruptures occur at an incidence of 1.2 per 100,000 persons per year, representing 10% of all biceps injuries. They are most common in the dominant arm of men in their fifth and sixth decades of life. Other risk factors include smoking, anabolic steroid use, and weight-lifting. The mechanism of injury is most commonly forceful eccentric extension of a flexed elbow. Proposed etiologies of distal biceps ruptures include decreased vascularity, impingement of the tendon against the radial tuberosity, and degenerative changes due to radial bursitis. There is a 2-cm hypovascular zone in the distal biceps between the perforators from branches of the posterior interosseous recurrent artery distally and the brachial artery proximally. With forearm rotation from supination to pronation, there is a 50% reduction of the space in the proximal radioulnar joint, with the distal biceps occupying 85% of the space in full forearm pronation.
Anatomy
The biceps functions as the primary supinator of the forearm and also contributes to elbow flexion, along with the brachialis muscle. The biceps muscle is innervated by a single branch of the musculocutaneous nerve 61% of the time at an average of 134 mm distal to the acromion. The biceps is formed by 2 muscular bellies, the long head and the short head, whose corresponding tendons continue as discrete units with well-defined attachments to the bicipital tuberosity. At the musculotendinous junction, the short head is medial to the long head. The distal biceps externally rotates as it approaches the radial tuberosity (right distal biceps spirals counterclockwise, whereas the left spirals clockwise) ( Fig. 1 A ). The long head, which is more radial, inserts proximally on the bicipital tuberosity, and makes up the bulk of the distal biceps tendon and functions as a powerful supinator. The short head inserts distally as it fans out over a larger surface area, allowing it to serve more as an elbow flexor. A bursa lies between the tendon and volar radius. The bicipital aponeurosis, or lacertus fibrosis, is a broad sheet of connective tissue that originates from the short head of the biceps and fans out medially to blend with the deep anterior forearm fascia, inserting onto the ulna. An intact lacertus fibrosis prevents proximal retraction of the distal biceps tendon.
The distal biceps footprint is on the posterior and ulnar aspect of the bicipital tuberosity, centered 30 to 65° anterior to the coronal plane with forearm fully supinated, allowing the tuberosity to increase the moment arm as well as serve as a cam with the forearm pronated ( Fig. 1 B). The bicipital tuberosity has a mean length of 22 to 24 mm and width of 15 to 18 mm, whereas the distal biceps tendon inserts in a ribbon-shaped configuration with mean dimensions ranging from 18 to 21 mm in length and 3 to 7 mm in width. Therefore, the footprint occupies only 63% of the length and 13% of the width of the biceps tuberosity.
Clinical evaluation
Diagnosis begins with a thorough history and physical. Distal biceps ruptures usually occur from a single traumatic event with sudden eccentric contraction while the elbow is flexed. Patients report a sudden sharp pain and sometimes an audible “pop.” Those with acute ruptures will demonstrate ecchymosis in the antecubital fossa with pain and weakness with resisted forearm supination. Patients may note some weakness with flexion, but this is more subtle, as the brachialis and brachioradialis are still competent to provide strong elbow flexion. In complete ruptures, there is a palpable absence of the distal biceps tendon with a hook test. O’Driscoll and colleagues described the hook sign, which is the inability to hook the examiner’s finger under the lateral edge of the intact biceps tendon when the elbow is flexed to 90° and the forearm is supinated. The hook test is reported to have a sensitivity and specificity of 100%. It is important to hook under the lateral edge of the tendon, as one could mistake the lacertus fibrosus as intact tendon. The squeeze test, as described by Ruland and colleagues, is 96% sensitive for diagnosing a complete distal biceps rupture. The patient sits relaxed with the elbow flexed at 60° and the forearm in slight pronation. When the examiner squeezes the biceps with both hands, the forearm should supinate if the biceps is intact. One may also note a “reverse Popeye sign,” from proximal retraction of the biceps muscle ( Fig. 2 ).
Partial ruptures can be difficult to diagnose. Those with partial ruptures will have pain with palpation over the distal biceps tendon and pain with resisted supination, but will have a palpably intact tendon. Ruch and colleagues found that partial distal biceps tears tended to involve disruption of the lateral side of the tendon insertion involving the short head of the biceps. The lateral portion of the tendon is more of the gliding portion and abuts the bursa and thus chronic inflammation of the bursa may make the lateral portion of the tendon more prone to rupture.
Plain radiographs will often be normal, but are important to obtain to assess for other elbow trauma. MRI is not necessary for a diagnosis in acute ruptures, but may be helpful in chronic ruptures to determine the level of retraction of the biceps tendon, in diagnosing partial ruptures, and in determining if the tear is at the insertion or at the musculotendinous junction. It is best if a FABS (flexed, abducted, and supinated) view is obtained, as this gives the clearest view of the longitudinal course of the biceps tendon and allows for optimal fat-suppressed images. The patient lies prone with the shoulder abducted 180°, the elbow flexed, and the forearm supinated. Ultrasound also can be used to diagnose distal biceps tears, but does not give the same level of detail as MRI.
Management
As patients lose a significant amount of supination strength without repair, surgery is recommended for those with complete distal biceps ruptures as long as they are fit to undergo an operation. With nonoperative management of a complete rupture, patients will lose 21% to 55% of supination strength, 79% of supination endurance, 10% to 40% of flexion strength, and 30% of flexion endurance. In a study of 22 middle-aged active men, Hetsroni and colleagues compared the outcome of 12 patients managed with early repair with those managed nonoperatively. Although there was no significant difference in functional outcomes, with 9 of 10 nonoperative patients reporting good to excellent outcomes, there was a mean loss of 20% of maximum flexion strength, 35% maximum supination strength, and 40% loss of supination endurance. Patients are often pain free but complain of weakness and easily fatigue with activities requiring forearm supination, such as use of a screwdriver. Acute repair should occur within 2 to 3 weeks of injury. Delay can lead to need for more extensile exposure as well as difficulties with mobilization and reduction of the tendon due to adhesion formation and loss of elasticity. With the 2-incision technique, complications are more common in repairs performed after 2 to 3 weeks.
Low-demand patients or those with significant medical comorbidities are not candidates for distal biceps repair. Patients with associated neurologic deficits that would inhibit a functional recovery would also not benefit from a repair. In addition, patients should be able to comply with the postoperative rehabilitation protocol and be willing to abide by activity limitations. Patients receiving workers compensation take longer to return to work and have worse Disabilities of the Arm, Shoulder, and Hand (DASH) scores.
In partial distal biceps ruptures, patients with high-grade tears (>50%) or those with persistent pain following conservative management also may benefit from surgical repair, although the management of partial tears is debatable. Debriding the distal biceps tendon in partial tears has been described, but most advocate for complete detachment and debridement, followed by reattachment of the distal biceps tendon.
Surgical approach
The 2-incision technique was initially described by Boyd and Anderson in an attempt to minimize anterior dissection and avoid complications associated with a large single incision. It went on to be modified by Kelly and colleagues, whereby the extensor carpi ulnaris (ECU) muscle is split and dissection of the supinator muscle and subperiosteal dissection of the ulna is minimized in an attempt to decrease the risk of radioulnar synostosis. With the development of new fixation techniques, such as suture anchors, cortical buttons, and biotenodesis screws, there has been a trend toward single-incision repairs in the past decade to limit the theoretic complications of heterotopic ossification and bridging radioulnar synostosis thought to be associated with the 2-incision technique.
Single-Incision Technique
For the anterior approach, either a longitudinal or transverse incision can be used. Longitudinally, the incision begins 1 to 2 cm distal to the elbow crease, medial to the brachioradialis muscle, and extends distally. A transverse incision, centered over the bicipital tuberosity, is more cosmetic and can be used in acute ruptures, but limits extension of the incision. For more extensive exposure in chronic cases or tendon reconstruction, a long S-shaped incision is typically used.
After incision through skin and subcutaneous tissue, care must be taken to identify and protect the lateral antebrachial cutaneous (LABC) nerve ( Fig. 3 A ). Proximally the interval is between the brachioradialis and brachialis, whereas more distally the interval is between the brachioradialis and pronator teres. The distal biceps tendon stump can be found proximally in a bursal sac. After control of the tendon is gained, the biceps tuberosity is exposed. The leash of radial recurrent vessels overlies the proximal radius and frequently needs to be ligated to expose the bicipital tuberosity and avoid a postoperative hematoma. The superficial radial nerve is deep to the brachioradialis muscle ( Fig. 3 B). The posterior interosseous nerve pierces the supinator muscle to lie on the dorsal radial cortex. It is important to keep the forearm fully supinated to protect the PIN when working around the bicipital tuberosity from the anterior approach.
Two-Incision Technique
In the 2-incision technique, the same anterior incision is used. The dorsal incision is made over the bicipital tuberosity, found by pronating and supinating the arm or using a blunt instrument through the anterior incision to tent the skin. Dissection is carried down through the common extensors, preferably the ECU, and the supinator is split, taking care to avoid exposure of the ulna. The forearm is placed in pronation for preparation of the bicipital tuberosity.
Single-Incision Posterior Technique
Kelly and colleagues described a single-incision technique using a posterior incision for partial distal biceps ruptures. This involves making an incision centered over the mobile wad centered over the tuberosity. The extensor digitorum communis fascia is split in line with the skin incision. With the forearm pronated, the supinator is split longitudinally over the radial tuberosity, exposing the biceps tendon at its insertion. Partial tears usually occur on the undersurface of the tendon. A stay suture is placed and the tendon is pulled out of the wound to expose the torn undersurface of the tendon. The intact tendon is then detached, any degenerative tissue is debrided, and the tendon is then repaired.
Surgical procedure
Exposure and Mobilization of the Biceps Tendon
In acute ruptures, the tendon can be identified in the proximal portion of the wound. In subacute ruptures, a pseudosheath can form as the tendon retracts. The tendon stump should be freed from scarring and adhesions to allow for full mobilization of the tendon. In chronic ruptures, tendon retraction can be limited by an intact lacertus fibrosis. However, with significant retraction, a second transverse incision proximally may be necessary to allow for extraction and mobilization of the tendon. In partial ruptures, the intact tendon can be traced down to its insertion on the tuberosity. Tourniquet deflation can aid in tendon retrieval in cases in which the tendon has retracted proximally. Endoscopic visualization has been described for visualization of the distal biceps tendon in partial ruptures to determine the extent of the tear.
Bicipital Tuberosity Preparation
No matter the fixation technique, the bicipital tuberosity is exposed and prepared. The forearm should be held at 90° of supination to minimize the risk to the PIN. The location of the drill hole for the suture anchor, cortical button, or tenodesis screw is determined. Fluoroscopy can aid in determining the correct location. All bony debris should be removed with judicious irrigation, and there should be minimal trauma to the periosteum to help prevent heterotopic ossification formation.
Tendon Preparation
Use a running, locking, braided, synthetic suture such as No. 2 FiberWire (Arthrex Inc., Naples, FL) to prepare the tendon, incorporating 3 to 4 cm of the distal tendon. Any degenerative distal tendon stumps should be debrided back to healthy fibers.
Fixation techniques
Bone Tunnel Fixation
Before the advent of more advanced fixation techniques, bone tunnel fixation using a 2-incision exposure was the standard of treatment. The distal biceps tendon is prepared as described previously through the anterior approach. With the forearm supinated, a hemostat is advanced along the medial border of the radius and into the dorsolateral forearm to help identify the site for the posterolateral incision. The forearm is pronated, which helps protect the PIN and brings the bicipital tuberosity into view. Through the posterolateral incision, the tuberosity is prepared by first inserting a guide pin, then drilling out the cortex so it can accommodate the tendon (usually a 10–15-mm oval-shaped hole). Next, 2 or 3, 2-mm holes are drilled through the lateral side of the radius. The sutures attached to the biceps tendon are shuttled into the posterior incision and then passed from the cavitation in the tuberosity and out the drill holes. The sutures are then tied across the bone bridges with the forearm in pronation.
Suture Anchors
This technique is performed through a single anterior incision. After exposure of the bicipital tuberosity, 2 suture anchors are placed ulnarly over the tuberosity to reproduce the insertion footprint of the biceps tendon. The advantage of suture anchors is that there is a reduced risk of PIN injury, as the posterior cortex is not drilled. However, biomechanical studies suggest that there is a lower load to failure (see later in this article). In addition, there is a risk of gapping between the distal biceps tendon and the bicipital tuberosity, as the tendon is not pulled into a bone tunnel.
Biotenodesis Screw
This technique also uses a single-incision approach. After exposure of the bicipital tuberosity, a guide pin is drilled through the tuberosity. The tendon width is measured and a drill hole is made in the bicipital tuberosity with a cannulated drill to accommodate the tendon in addition to the biotenodesis screw. The tendon is prepared with a No. 2 nonabsorbable suture, which is then passed through the biotenodesis screw. The distal end of the tendon is passed to the screw tip. The screw and the tendon are advanced into the hole and screwed flush with the tuberosity.
Cortical Button
Bain and colleagues first described the use of a suspensory cortical button for distal biceps repair. After exposure and mobilization of the tendon, the bicipital tuberosity is prepared. In the technique originally described by Bain and colleagues, a slotted Beath pin is drilled from anterior to posterior through the bicipital tuberosity. Drilling should be slightly ulnarly to minimize risk of injury to the posterior interosseous nerve. Care also must be taken to avoid overdrilling beyond the far cortex, as to avoid damage to the dorsal soft tissues, in particular, the PIN. A cannulated drill is then used to overdrill both cortices to accommodate the button. The anterior hole is enlarged with a surgical burr or an appropriately sized cannulated drill (typically 7–9 mm) to accommodate the width of the tendon. The tendon is prepared with a running, locking synthetic suture with the 2 tails placed through the 2 middle holes of the cortical button. Note that 2 to 3 mm of suture must be left between the distal tendon stump and the cortical button as to allow the button to pass through the dorsal cortex and be flipped. Two separate sutures are passed through the 2 outer holes of the cortical button; these will act as control sutures. The Beath pin is then passed through the drill hole and out the dorsal forearm soft tissue. The sutures are then toggled and pulled to flip and lock the button over the dorsal radial cortex. An appropriately tensioned biceps tendon will feel taut with the elbow extended. Fluoroscopy is used to confirm the cortical button is secured against the dorsal radial cortex. Gapping between the cortical button and the dorsal cortex can lead to entrapment of dorsal compartment soft tissues, including the PIN.
Sethi and Tibone described the “tension-slide” use of the cortical button. This obviates the need to predetermine the length of suture between the button and the biceps. It also eliminates the need to pass a Beath pin or needle through the dorsal forearm, thereby decreasing the risk of injury to the PIN. After tendon preparation, one strand of suture is threaded through the left and then back up through the right hole of the cortical button. Similarly, another suture is threaded in the opposite direction, through the right and then back up the left hole of the cortical button, so that the suture ends face the biceps tendon. The guide pin is drilled from anterior to posterior over the radial tuberosity. The anterior cortex is prepared with a cannulated drill after sizing the diameter of the distal biceps tendon ( Fig. 4 A ). The button inserter is used to push the button with an attached distal biceps tendon through the prepared radial tuberosity hole ( Fig. 4 B). Tension is pulled on the strands to secure the button down ( Fig. 4 C). Fixation can be supplemented with an interference screw to push the distal biceps insertion ulnarly, in a more anatomic position ( Fig. 4 D). The “tension slide” technique with a cortical button has been shown to lead to less gap formation, but this has not translated into clinical outcome improvements.
Siebenlist and colleagues reported good outcomes when using intramedullary cortical button fixation, which, in theory, minimizes the risk of PIN injury. In addition, by using double intramedullary buttons, more anatomic repair of both heads of the distal biceps can be performed to its footprint.
Single-Incision Power Optimizing Cost-effective Technique
Tanner and colleagues recently reported on the SPOC (single-incision power optimizing cost-effective) method of distal biceps repair. This technique is thought to reattach the biceps tendon onto the more anatomic posterior and ulnar surface of the radius, thereby maximizing supination strength, but using a standard single anterior incision ( Fig. 5 ). This is an intraosseous suture technique using two 2.5-mm drill holes over the bicipital tuberosity. Using suture shuttles, the distal biceps tendon is repaired down to the posterior aspect of the drill hole over the tuberosity, back to its more anatomic and biomechanically advantageous position.
Comparison of fixation techniques
Biomechanical Comparison
The repaired distal biceps needs to allow for early active range of motion in the postoperative period. The mean force required to actively flex the elbow ranges from 25 N at 30°, up to 67 N at 130° of elbow flexion. The force required to rupture the intact distal biceps is approximately 200 N. Current fixation methods include bone tunnels, suture anchors, biotenodesis screws, and cortical buttons. Traditional bone tunnel techniques fail through fracture between the bone tunnels, suture breakage, and the suture cutting. A systematic review in 2008 found that the cortical button had the best pullout strength. However, most current repair techniques approach native tendon strength ( Table 1 ). Adding an interference screw to the cortical button construct does not add strength to the construct. However, it enables a more anatomic construct by pushing the distal biceps more ulnarly, closer to the anatomic footprint on the bicipital tuberosity, which may improve clinical outcomes.
| Study | Bone Tunnel | Suture Anchor | Interference/Tenodesis Screw | Cortical Button |
|---|---|---|---|---|
| Greenberg et al, 2003 | 178N | 254N (Mitek G4 Super) | — | 584N |
| Lemos et al, 2004 | 203N | 263N (Super Mitek × 2) | — | — |
| Idler et al, 2006 | 125N | — | 178N | — |
| Spang et al, 2006 | — | 230N (5 mm × 2) | — | 275N |
| Krushinski et al, 2007 | — | 147N (3.5 mm × 2) | 192N (8 mm) | — |
| Kettler et al, 2007 | 210N | 196–225N (Various) | 131N (5.5 mm) | 259N |
| Mazzocca et al, 2007 | 310N | 381N | 232N | 440N |
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