Epidemiology, Etiology, Anatomy, History, Examination, and Imaging
- Samuel A. Taylor, MD
- Frank A. Cordasco, MD, MS
Abstract
Distal biceps ruptures are most common among middle-aged men and occur most commonly in the dominant arm and is associated with the following risk factors: smoking, history of anabolic steroid use, chronic renal disease, elevated body mass index, and history of contralateral rupture. Mechanism of injury may be related to a hypovascular zone of the tendon, mechanical impingement in the proximal radioulnar joint, and attritional interstitial tendon weakness. The insertion of the distal biceps is often bifid in nature, with separate long and short head attachments to the radial tuberosity. Physical examination maneuvers can be helpful in diagnosing this injury. Magnetic resonance imaging is very useful in assessing injury and extent of injury preoperatively.
Keywords : Distal biceps tendon, elbow, epidemiology, long head biceps, short head biceps
Important Points
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Risk factors for distal biceps tendon ruptures include male gender, dominant arm, and history of contralateral distal biceps rupture, smoking, corticosteroid use, anabolic steroid use, or chronic renal disease, and increased body mass index.
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Etiology is thought to be related to a hypovascular zone, mechanical impingement, and attritional interstitial tendon weakness.
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Distal biceps insertion may include a common tendon or a bifid attachment of the short and long heads on the radial tuberosity.
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Several different physical examination maneuvers, including the hook test, have been described to identify distal biceps tendon ruptures.
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Magnetic resonance imaging (MRI) is important to evaluate for extent of injury, quality of tendons, nature of injury, and extent of retraction.
Epidemiology
One report suggested that the incidence of distal biceps tendon ruptures was 1.2 per 100,000 patients per year ( ). A later study using the PearlDiver Technologies database, however, found an annual incidence of 2.55 per 100,000 patient-years; the average age of patients was found to be 46 years with an overwhelming (95%) male predominance ( ). Furthermore, the dominant arm is more commonly affected (86%) ( ), and a personal history of distal biceps rupture is a significant risk factor for contralateral rupture (8%) (Green et al, 2012). Additional established risk factors include smoking, anabolic steroid use, systemic corticosteroid use, chronic renal disease, and increased body mass index. Smoking specifically has been a significant risk factor and was found in one study to impart a 7.5-fold higher risk for distal biceps rupture than nonsmoking (Green et al, 2012; ).
Etiology
Although the exact etiology of distal biceps rupture is not yet fully elucidated, proposed an anatomic and mechanical rationale. Through cadaveric dissections, these investigators demonstrated a 2.1-cm hypovascular zone in the distal biceps tendon occurring between vascular contributions from the brachial artery proximally and the posterior recurrent artery distally. Furthermore, they used dynamic cross-sectional computed tomography (CT) images to show that the distance between the proximal radius and ulna was 52% shorter with the forearm in full pronation than in supination. Stated another way, the distal biceps tendon occupied nearly 85% of the space between these two bones with the arm in pronation, suggesting that some form of mechanical impingement coupled with the aforementioned vascular watershed leads to progressive tendon weakness and ultimately to tendon failure ( ).
Anatomy
The biceps muscle acts as a secondary flexor of the elbow and the primary supinator of the forearm. It has two proximal origins, or heads: the long head, which inserts on the supraglenoid tubercle, and the short head, which meshes with the coracobrachialis tendon to form the conjoined tendon on the coracoid process. Traditionally, the biceps has been thought to have a singular insertion onto the bicipital or radial tuberosity; however, later studies (discussed here) suggest otherwise. The lacertus fibrosus (bicipital aponeurosis) emanates from the biceps muscle belly at the level of the musculotendinous junction and crosses distally and medially to insert along the subcutaneous border of the ulna.
demonstrated that, in contrast to traditional teaching, there are normal variations among distal biceps tendons that include two distinct distal long head and short head tendon insertions. Others have reported bifurcate distal biceps tendon insertions in 25% to 60% of cadaveric specimens studied ( ). Voleti et al (2016) have reported on three isolated short head biceps tendon repairs ( Fig. 30A.1 ). They found all three cases to successfully return to baseline level activity following anatomic repair of the short head component with or without the independent repair of the long head component. Other groups inserted the long head of the distal biceps tendon along the proximal aspect of the bicipital tuberosity whereas the short head inserted more distally ( ) and accounted for the majority (60%) of footprint coverage ( ). The bicipital tuberosity has been shown to be 21 to 22 mm in length and 7 to 15 mm in width ( ). , in an evaluation of 18 fresh-frozen cadaveric elbows, noted similar dimensions of the radial tuberosity as well as a ribbon-shaped distal biceps morphology.
The biceps footprint has been shown to be along the posterior/ulnar aspect of the radial tuberosity ( ) to maximize functional supination of the muscle tendon unit. examined the biomechanical contributions of the short and long head attachments in six cadaveric specimens and found that the short head contributed the greatest to supination strength in the neutral and pronated forearm, whereas the long head attachment was more efficient with the forearm supinated.
For surgical exposure purposes, it should be noted that the radial recurrent artery most commonly crosses volar to the distal biceps tendon at an average of 4 mm proximal and 15.4 mm volar to the radial tuberosity. The radial recurrent artery bifurcates nearly half the time at an average of 9 mm from its origin ( ).
History and Physical Examination
Distal biceps tendon rupture frequently results from an acute injury in the setting of a heavy eccentric load applied with the elbow in 90 degrees of flexion. Although the most common injury pattern is avulsion of the biceps tendon from the radial tuberosity, some writers have reported intratendinous and musculotendinous locations of injury ( ) as well as isolated short head biceps avulsions (Voleti et al, 2016).
History should be obtained from the patient to check for important risk factors, such as prodromal symptoms prior to the acute event, contralateral distal biceps tendon rupture, hand dominance, and tobacco and anabolic steroid use. One should elicit the patient’s mechanism of injury and resulting symptoms, such as the often-described sudden, sharp, painful “pop.” The sharp pain typically resolves within hours to days and may be followed by a dull ache and ecchymosis. Some describe elbow flexion and more pronounced supination weakness. This description may come in the form of newfound difficulties with activities that require these actions, such as turning a doorknob and lifting objects.
Physical examination includes inspection and palpation. Ecchymosis is often evident in the acute setting. The visible deformity resulting from unchecked retraction of the biceps muscle belly has been termed a “reverse Popeye sign” and may be considered pathognomonic for such an injury. It is critical to remember, however, that competency of the lacertus fibrosus is variable following avulsion injury. If the lacertus remains intact, it acts as a checkrein to proximal migration of the tendon and muscle belly and can masquerade as an intact tendon.
Examination of the antecubital fossa typically reveals a void where the biceps tendon inserted.
Range of motion and strength testing is performed, particularly with respect to flexion and supination. compared side-to-side isokinetic elbow flexion and forearm supination strength and endurance in nine patients with untreated unilateral distal biceps ruptures and found that peak torque was nearly 50% lower in the affected arm for both flexion and supination. Results of fatigue testing in affected and normal arms, however, were not significantly different.
Several important tests have been described in the literature to improve our diagnostic capabilities in the office. The hook test, originally described by , is perhaps the most commonly employed test for distal biceps ruptures ( Fig. 30A.2 ). Of the 45 patients in their study, 33 had complete ruptures and 12 had partial tears. Results of the hook test are positive in all complete tears and negative in all partial tears. Of the 12 patients in this group with partial tears, 9 deemed the hook test painful despite structural integrity. The investigators claimed that the hook test was more sensitive (100% vs. 92%) and specific (100% vs. 85%) than MRI for complete tears. described the biceps crease interval test to aid in the diagnosis of distal biceps tendon ruptures. They measured the distance between the antecubital crease the elbow and the distal descent of the biceps muscle, which they called the “biceps crease interval.” A biceps crease interval greater than 6 cm or a biceps crease ratio (injured to uninjured side) greater than 1.2 resulted in 96% sensitivity and 93% accuracy for distal biceps tendon ruptures. described the passive forearm pronation test. suggested the supination-pronation test in the acute setting to aid in diagnosis. With the elbow in 90 degrees of flexion, the forearm is pronated and supinated with attention to the biceps contour. In the intact distal biceps, the biceps muscle belly shortens in supination and elongates in pronation. A positive result is determined by a failure of elongation of the muscle as the forearm is actively pronated.
evaluated the efficacy of the hook test, the passive forearm pronation test, and the biceps crease interval test in 48 patients with suspected distal biceps tendon injuries. They found 100% sensitivity and specificity when results of all three tests were all positive.
Imaging
Though often unrevealing, plain radiographs should be obtained to evaluate for osseous abnormalities such as heterotopic ossification, excrescences of the radial tuberosity, and concomitant pathologies.
MRI is an important diagnostic tool that can be particularly useful to assess the extent of injury in a partial tear and to evaluate for the degree of proximal retraction and the presence of tendinosis within the retracted tendon during preoperative planning ( Fig. 30A.3 ). evaluated the sensitivity and specificity of MRI to determine partial and complete distal biceps tendon ruptures by having two radiologists who were blinded to the intraoperative observation review preoperative MR images from 22 patients with partial tears, 24 patients with complete tears, and 10 asymptomatic controls. These investigators determined that MRI was 92.4% sensitive and 100% specific for distal biceps tendon tears. Sensitivity for complete tears was 100%, but specificity lagged behind at 82.8%. The sensitivity for partial tears was only 59.1% but the specificity was 100%.
Ultrasound can be a useful adjunct and has been shown to be 95% sensitive and 71% specific with 91% accuracy for complete versus partial distal biceps tendon ruptures ( ). It remains, however, a fairly user-dependent imaging modality.
Treatment, Outcomes, Complications, and Rehabilitation
- Samuel A. Taylor, MD
- Frank A. Cordasco, MD, MS
Abstract
Early operative treatment for distal biceps tendon ruptures leads to superior clinical outcomes. Although two-incision techniques achieve a more anatomic reinsertion of the distal biceps tendon than single-incision techniques, superiority of one technique over the other has not been demonstrated clinically. The overall complication rate for distal biceps tendon repair is relatively high regardless of technique but the complication profiles are different, in that heterotypic ossification is more common among patients treated with two-incision techniques and neurologic complications more common among those treated with single-incision techniques. Fixation measured at the time of the repair is strongest with cortical button fixation, but no clinical differences have been found among the various fixation methods.
Keywords : distal biceps tendon, rehabilitation, surgical approach
Important Points
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Nonoperative treatment may result in persistent clinical symptoms, including pain and weakness of elbow flexion and supination.
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Two-incision repair techniques theoretically provide a more anatomic repair of the distal biceps footprint but have a relatively high incidence of postoperative heterotopic ossification and postoperative fatty infiltration of the supinator muscle.
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Single-incision techniques require less surgical dissection, may result in a biomechanically less anatomic repair location on the radial tuberosity, and have higher rates of transient neurologic complications such as lateral antebrachial cutaneous and superficial radial nerve paresthesias.
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Multiple fixation methods have been described, including cortical buttons, suture anchors, transosseous sutures, and bone tunnels.
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Although biomechanical studies suggest cortical button fixation to be strongest at the time of the repair and the single-incision and two-incision approaches have different complication profiles, there is no clinical data to suggest superiority of a specific surgical approach or method of fixation.
Surgical Treatment
Although nonoperative treatment of distal biceps tendon ruptures may produce acceptable clinical results ( ), ultimate supination strength in the unrepaired arm is decreased by nearly 40%. found peak torque to be lower for flexion and extension following distal biceps ruptures. These strength deficits, along with the patient profile (active male, fifth decade of life, and dominant side) as well as the detrimental effects of delayed surgical intervention have led surgeons to regard surgery as the conservative treatment in this population.
Once the decision has been made for a patient to undergo primary repair of an acute distal biceps tendon rupture, there are two general decisions to be made: (1) the surgical approach and (2) the method of fixation.
Single-Incision Versus Two-Incision Technique
With regard to surgical approach, one may consider either a single-incision or a two-incision technique. Similar clinical and functional outcomes have been reported between the two approaches, but their complication profiles are somewhat different as are the purported biomechanics. The primary advantages of a single-incision approach are a less extensive surgical exposure and lower incidence of heterotopic ossification than that reported for the two-incision approach. The primary disadvantage is a higher prevalence of neurologic complications, such as lateral antebrachial cutaneous nerve and superficial radial nerve paresthesias secondary to retraction ( ).
Proponents of the two-incision technique argue that the single-incision technique fails to achieve anatomic reinsertion of the distal biceps tendon, consequently decreasing footprint coverage and ultimately reducing supination strength after repair. In fact, several studies exist to support this claim. noted that a single-incision exposure failed to achieve anatomic restoration of the footprint in 35% of specimens they studied. The two-incision approach more accurately covers the anatomic footprint and theoretically leads to improved function. demonstrated in a cadaveric study that a significantly larger portion of the distal biceps footprint is covered (73.4% vs. 9.7%) after a two-incision technique than after a single-incision technique.
Biomechanical data would suggest an advantage of greater footprint coverage. observed that a more anatomic repair of the distal biceps tendon footprint on the ulnar side of the bicipital tuberosity increased supination torque by 15% in comparison with nonanatomic repairs with the arm in neutral rotation and by 40% in comparison with such repairs with the arm in 45 degrees of supination.
It should be noted, however, that the cost of the more anatomic ulnar/posterior position of the tendon repair site on the bicipital tuberosity that is gained by a two-incision approach may come in the form of increased rates of radioulnar heterotopic ossification ( ). The two-incision technique has been found to result in increased supinator fat content as well ( ). Increased risk of heterotopic ossification with the two-incision technique has led some surgeons to suggest using indomethacin as prophylaxis ( ). In the event that heterotopic ossification results in significant functional limitations, it may be excised. reported excellent results at 1-year follow-up for eight patients who were treated with heterotopic ossification excision in comparison with eight matched patients who underwent uncomplicated distal biceps tendon repairs with only 14 degrees of loss in rotation arc (151 degrees vs. 165 degrees) for forearm rotation. Ultimately, however, these patients experienced no differences in strength or outcome scores, although it would be best to avoid heterotopic ossification and the need for a second operation.
Method of Fixation
The next decision that must be made is method of fixation. Various fixation methods have been described in the literature, including transosseous tunnels, suture anchors, cortical buttons, and interference screws. Various combinations of fixation techniques have also been described. Although cadaveric biomechanical studies suggest that cortical button fixation is strongest at the time of repair, there is little clinical data to suggest the clinical relevance of this finding. In fact, the outcomes reviewed in the following discussion do not show any clinically significant differences among fixation techniques.
, utilizing 12 matched pairs of cadaver elbows to compare suture anchor with bone tunnel repair, determined that bone tunnel fixation resulted in greater strength and stiffness. The bicipital tuberosity acts as a mechanical cam for the distal biceps tendon to improve supination strength. As a result, some writers have emphasized the importance of an anatomic repair of the distal biceps tendon to the ulnar side of the radial tuberosity and others have examined the impact of the iatrogenic effects of repair technique on tuberosity morphology and supination strength. examined the effect of repair technique on proximal radioulnar impingement and concluded that onlay suture anchor–type repairs resulted in the lower biceps tendon-to-ulna distances than trough or tunnel techniques in neutral rotation and pronation. They suggested that suture anchor techniques might therefore result in iatrogenic proximal impingement during pronation. demonstrated the importance of preserving the normal morphology of the radial tuberosity during distal biceps tendon repair. Their cadaveric study used 10 matched specimens to compare the effect of repair technique, specifically trough repairs with onlay repairs, on supination strength. Trough repairs exhibited a 27% lower supination moment in 60 degrees of forearm supination with a reduction of tuberosity height of 3 mm.
Outcomes
Review of the literature does not demonstrate a single surgical exposure, technique, or method of fixation to be clinically superior. The complication rates are similar, but the types of complications vary ( ).
conducted a randomized trial comparing single-incision suture anchor repair with two-incision transosseous repair techniques. No significant differences were found for patient-reported outcomes. Final isometric supination strength testing was 10% greater for the two-incision group (104% vs. 94%). compared a single-incision cortical button technique with a double-incision technique and found no differences for range of motion or strength at final follow-up. Complication rates were higher, however, for the single-incision technique, with paresthesias of the superficial radial nerve being most common. In a separate study prospectively evaluated 15 patients who underwent a biceps repair using a posterior approach; this cohort was compared with a randomized selection of 17 anterior repair recipients. Quantitative MRI analysis determined the insertion site angle of the tendon, and supinator fat content and supination strength were measured in three forearm positions. The anterior approach group had a significantly higher nonanatomic insertion site angle of the tendon than the control group and the posterior group ( p < .001). The posterior approach group had significantly greater supinator fat content ( p ≤ .019) than both the control group and the anterior approach group. After repair, the posterior approach group had significantly greater supination strength than the anterior approach group ( p = 0.027). The researchers concluded that future studies should focus on restoring the anatomic footprint without damaging the supinator muscle.
Two systematic reviews have investigated the clinical relevance of surgical exposure and method of fixation without determining an optimal technique. looked at data from 1074 patients compiled from 40 articles. They compared clinical outcomes of four different fixation methods (suture anchors, bone tunnels, interference screws, and cortical buttons). Although complication rates were lower for the double-incision approach with bone tunnels, the researchers noted no significant differences for postoperative range of motion or strength of flexion or supination. performed a systematic review comparing the complication rates for different surgical approaches and repair constructs. They studied a total of 498 elbows from 22 studies. With regard to approach, they found no significant difference between single-incision and double-incision approaches with respect to complications (33.9% vs. 25.7%). Intraosseous screw fixation had a higher complication rate (44.8%) than suture anchors (26.4%), bone tunnels (20.4%), and cortical buttons (0%). Lateral antebrachial cutaneous nerve injury was the most common complication (11.6% for single-incision approach and 5.8% for double-incision approach).
Furthermore, it can be stated that overall complication rates are quite high (36% to 52%) for primary repair of the distal biceps regardless of surgical approach or method of fixation. A wide array of complications has been reported, including neurologic problems, vascular complications, and construct failures. reported posterior intraosseous nerve palsy, lateral antebrachial cutaneous paresthesias, superficial radial nerve dysesthesias, brachial artery thrombosis, and failures (retear of the construct). Furthermore, cited an overall 42% complication rate in 50 patients who underwent single-incision repair using the Endobutton (Acufex Microsurgical, Inc, Mansfield, MA). Lateral antebrachial cutaneous nerve injury was the most common complication (36%). A posterior interosseous nerve, anterior interosseous nerve, and superficial radial nerve were each identified in 4% of patients.
Failure of fixation in the form of retear is very uncommon, occurring in approximately 1.2% to 2% of cases ( ). , reviewing a cohort of 190 patients with more than 1-year follow-up, observed a failure rate of 1.5%. reported on 198 consecutive distal biceps repairs and found a 36% complication rate, including lateral antebrachial cutaneous nerve paresthesias (26%), superficial radial nerve paresthesias (6%), superficial infection (2%), posterior interosseous nerve injury (4%), symptomatic heterotopic ossification (3%), and rerupture (2%), with an overall reoperation rate of 3%.
On a separate note, suggested that significant interstitial stretch occurs in the biceps muscle in the setting of retracted distal biceps ruptures requiring repair in varying degrees of elbow flexion. In their case-control series of 188 distal biceps repairs, these investigators identified 23 cases (19 chronic and 4 acute) that required repairs in greater than 60 degrees of elbow flexion. Average end range of motion was 3 to 138 degrees. Although 3 of the 23 patients reported easy fatigability, all returned to work and reported satisfaction. One of the 23 patients was found to have rerupture through the myotendinous junction. These clinical results suggested that retracted distal biceps repairs can effectively be performed primarily without the need for allograft reconstruction.
Authors’ Preferred Surgical Technique
See 
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- Video 30B.1
Authors’ preferred technique (single incision) for distal biceps tendon rupture.
Repair of Acute Biceps Tendon Rupture
The patient is placed in the supine position with a hand table after administration of regional anesthesia. In most cases we prefer a sterile tourniquet to avoid compromising the exposure during the skin preparation and draping. A transverse incision is made distal to the skin crease of the antecubital fossa. A mini–C-arm fluoroscopy unit is utilized to identify the radial tuberosity, which is usually 3 to 4 cm distal to the antecubital fossa. This maneuver facilitates minimizing the length of the transverse incision, particularly in large patients with increased subcutaneous tissue. Neurovascular structures are protected during the superficial approach. The lateral antebrachial cutaneous nerve is identified and retracted laterally with the brachioradialis muscle. The stump of the distal biceps tendon is often retracted proximally and is located superficially just under the skin and subcutaneous tissues ( Fig. 30B.1 ). We prefer a unicortical tensioning button (Arthrex Inc., Naples, FL) for fixation. Although we have used a bicortical button technique with a socket and screw, which has some theoretical advantages, we have not found it to be clinically superior; since it requires slightly more surgical time, higher implant-associated expense, and greater potential risks, such as fracture, we have favored the unicortical technique for the past few years. The tendon is prepared by utilizing a #2 FiberLoop (Arthrex) stitch, which is then secured to the button. After the unicortical drill hole is prepared on the distal and ulnar aspect of the footprint with the forearm in maximum supination, the button is deployed and tested to confirm that it is locked on the endosteal surface of the intramedullary canal. Pulling the tendon to the footprint and thereby reducing it anatomically completes the tension slide technique. The suture limbs are tied while tension is maintained after one limb is passed through the tendon to secure the fixation. In patients with larger radial tuberosity footprints we occasionally use more than one button or augment the repair with a suture anchor. The wound is closed in layers and a subcuticular skin closure completes the repair.
