Distal biceps tendon rupture: a comprehensive overview

Abstract

• Distal biceps tendon (DBT) is a relatively rare injury mainly occurring in middle-aged men while in eccentric biceps muscle contraction.

• Clinical appearance with proximal avulsion of the muscle and specific clinical tests are most of the time sufficient for diagnosing DBT, but if needed ultrasonography and MRI, most often in FABS view, can be used to ensure diagnosis of DBT and partial DBT.

• Surgical anatomical reinsertion has shown to be a successful method of treatment, although conservative treatment can be initiated in older patients.

• Two different approaches are described in literature: single- and double-incision techniques with different fixation methods proving to have similarly good results.

• Major complications of surgical intervention are posterior interosseous nerve palsy and symptomatic heterotropic ossification.

• Overall outcome of surgical intervention has shown high subjective satisfaction with slight weakness in flexion and supination but mostly without loss in range of motion.

Anatomy

The biceps tendon, as the name suggests, originates as two headed muscle with a long head and a short head from the supraglenoid tubercle and coracoid process, respectively. Distally the muscle inserts as one tendon into the radial tuberosity while an aponeurosis, the lacertus fibrosus, envelopes the proximal part of the flexor muscles of the forearm and inserts into the proximal medial side of the forearm (proximal ulnar and antebrachial fascia). The biceps brachii is innervated by the musculocutaneous nerve, originating from C5-C7, and is supplied by branches of the brachial artery.

Function

The main function of the biceps brachii is the flexion and supination of the forearm due to distal insertion at the radial tuberosity of the short head and proximal insertion at the radial tuberosity of the long head, respectively (Fig. 1). Therefore, the short head contributes to a greater flexion force and the long head to a greater supination force (1, 2). Additionally, due to the origins at the scapula the biceps also flexes the arm at the glenohumeral joint (1).

Figure 1.

Radial tuberosity with proximal insertion of the long head (LH) and distal insertion of the short head (SH). Copyright MoRe foundation.

Epidemiology

Although proximal biceps tendon rupture of the long head is more common, with more than 50% of all biceps ruptures, the literature is more investigated and controversial in the rupture of the distal biceps with 3% of all ruptured biceps. Distal biceps tendon ruptures are relatively uncommon with an incidence of 1.2–2.55 per 100 000 (3, 4). Another study in the Finnish and Swedish population suggests an increase in the incidence of distal biceps rupture from ca. 1 in 2001 to ca. 6 in 2015 (5). More than 95% of patients are middle-aged males, usually with an active lifestyle of heavy lifting (3).

Aetiology

The most common way of rupturing the distal biceps tendon is due to applied forces on the eccentric contraction of the biceps typical in weightlifting during elbow flexion and abrupt elbow extension (6) (Supplementary Video 1, see section on supplementary materials given at the end of this article).

Risk factors and pathophysiology

Mostly an underlying degenerative factor including smoking, increased BMI, overuse and age in combination with forceful biceps movement leads to a ruptured biceps. Smoking is a significant risk factor for tendinopathy by reducing blood supply (2). Overuse and biceps tendon impingement, leading to inflammation, friction and degeneration of the tendon, also play an important role (7). An increased height and volume of the radial tuberosity might lead to impingement and friction, followed by distal biceps tendon pathologies (8). Del Buono et al. have shown that obesity reduces the immune response to tendon injury (9) leading to 36–66% of cases being obese (3, 4). Corticosteroids degenerate tendon strength by reducing the activity of fibroblast (10) and anabolic steroids result in excessive muscle strength leading to a higher amount of stress on the tendons (11). Less common risk factors are the usage of statins and quinolones (12, 13), gout, diabetes and chronic kidney disease.

Diagnosis

Clinical diagnosis

Typical symptoms of biceps tendon rupture include pain, ecchymosis, oedema and sometimes a popping sound might be heard during the act of rupture. Furthermore, palpation of the footprint of the radial tuberosity elicits pain in situations of rupture, partial tear or tendinitis (14). The avulsion of the distal biceps tendon leads to weakness in the elbow and proximal retraction of the muscle belly (Fig. 2). As a consequence, decreased strength in flexion by 30–40% and decreased strength in supination by over 50% is commonly seen (15). Another case study suggests an initial strength reduction of flexion and supination by 17–21% and 13–19%, respectively (16). Although strength loss is noticeable at first, chronic biceps tendon rupture and recovery of acute biceps tendon injury do not always show great deficits in strength and endurance due to compensation of the brachialis muscle (16).

Figure 2.

Complete distal biceps tendon rupture: proximal retraction. Copyright MoRe foundation.

There are several clinical tests to confirm a complete distal biceps tendon rupture. The hook test, described by Shawn O’Driscoll, is performed with the patient’s elbow 90 degrees flexed and supinated. The examiner then hooks a finger under the distal biceps tendon from the lateral side. It is important that the hook test should not be performed from the medial side as a false negative result might appear by hooking under the intact lacertus fibrosus. In a ruptured biceps, the tendon has moved proximally so that there is no structure to hook the finger under. In partial biceps tendon rupture, the hook test is neither positive nor negative as the tendon structure is felt, but with a different feeling compared to the contralateral side. In his cohort, the hook test was painful in 75% of the time but the sensitivity and specificity were 100% (17). The biceps squeeze test, developed by Ruland RT et al., is performed with the elbow flexed between 60 degrees and 80 degrees and a slight pronation. The examiner then squeezes the biceps brachii belly firmly resulting in a supination in case of an intact biceps tendon or no movement in case of a ruptured tendon (18). The supination–pronation test is performed by moving the forearm of the patient into supination and pronation. During supination, the biceps are bulked up while in pronation the biceps are elongated. In a ruptured biceps, these changes are not visible (19). The fourth test is the biceps crease interval where the length between the antecubital fossa and the distal biceps muscle is measured. The test is positive with a measurement of more than 6 cm or a biceps crease ratio of more than 1.2. This seems quite reliable as the test offers a 96% sensitivity (20).

In a recent study, by Caekebeke et al., there has been a suggestion for a clinical test to diagnose partial biceps tendon rupture and tendinitis. The distal biceps provocation test is performed by flexing the elbow with resistance at 70 degrees angle in the pronated and supinated forearm position. A positive test result can be found when the pain is bigger during the pronated resisted flexion than in the supinatedresisted flexion due to compression of the tendon during pronation (21).

Clinical examination is most of the time sufficient to diagnose a full biceps tendon rupture (22). In cases of doubt and partial rupture, MRI or ultrasonography might be needed (23, 24), although the latter method is highly user dependent.

Ultrasonography is widely available and inexpensive to use, while MRI seems to have a higher accuracy with 86.4% compared to ultrasonography with 45.5% in complete rupture. In partial rupture, the accuracy between ultrasonography and MRI were identical with 66.7% (Table 1) (25). Festa A et al. reported a sensitivity and specificity for MRI of 100% and 82.8% in complete rupture, respectively, and 59.1% and 100% in partial rupture, respectively (26).

Table 1.

Accuracy of MRI and ultrasonography (USG) in complete and partial rupture (31).

	MRI	USG
Complete rupture	86.4%	45.5%
Partial rupture	66.7%	66.7%
Total	80.6%	51.6%

Since 2004 a new position by Giuffrè et al. has been suggested for imaging the distal biceps tendon for MRI, the flexion–abduction–supination view (FABS), allowing the examiner to observe the biceps tendon from the musculotendinous junction to its insertion usually in one image (27). The patient therefore has to be placed in a prone position with the arm fully abducted above his head, his elbow flexed by 90 degrees and forearm supinated (Fig. 3). Contradictory to two studies published in 2020 and 2021, the FABS position did not show significant superiority in sensitivity and specificity compared to other imaging positions (28, 29). Schenkel et al. also showed that the inter-rater reliability was higher in the FABS view and the accuracy of grading the extent of pathology was better than in surgical grading (29).

Figure 3.

(A) Flexion–abduction–supination view (FABS), (B) FABS MRI of a healthy tendon showing the whole tendon (from musculotendinous junction to insertion) in one image. Copyright MoRe foundation.

Therefore, in order to diagnose distal biceps tendon rupture, clinical diagnosis should be performed first. If the examiner is unsure, ultrasonography (USG) should be used depending on the experience of the examiner. In case of unclear USG evaluation, MRI should be used. USG and MRI are also suitable in suspicion of partial tendon rupture.

Treatment

As mentioned in clinical diagnosis, strength and endurance loss is a common symptom of complete distal biceps tendon rupture and therefore is usually treated surgically (30). Morrey et al. showed in his biomechanical study a mean loss of 40% in supination and a mean loss of 30% in flexion in patients treated conservatively compared to immediate anatomical reattachment (31). Therefore, conservative treatment is a viable option in very low-demand patients having concerns about problems connected to the surgery, but surgical treatment should be striven for (32).

Partial tears are usually treated conservatively first (suggestion of 6 months) (7) and if unsatisfactory results occur, a surgical treatment is suggested (32). In a cohort study in 2010, 82% of participants had a failed non-surgical treatment (33) and in a more recent study by Bauer et al., they concluded a failed non-surgical treatment of 55.7% (34). In this study, high-need patients reported a better recovery, if they undergo surgery compared to those of non-surgical treatment. Typically, a conservative treatment is recommended initially, if less than 50% of the tendon is involved in a partial tear, while more than 50% involvement in a surgical approach is recommended (35).

In chronic biceps tendon rupture, scarring and a proximally retracted tendon, unless the lacertus fibrosus is intact, cause difficulties in anatomical tendon reinsertion (36). Therefore, non-surgical treatment is a viable option, especially when taking the mentioned difficulties into consideration. Anatomical reinsertion is the desired surgical approach due to a high unsatisfactory results rate of 40% in non-anatomical insertion (37). Morrey et al. suggest to perform primary distal biceps tendon repairs in up to 90 degrees of flexion as the outcome has shown to be good. In the postoperative state, full extension could be achieved with a low rate of complications (38). Similar results have also been shown by Bosman et al. (39). In cases where the tendon cannot be reinserted into the radial tuberosity or the tendon appears to be poor in quality, an auto- or allograft can be used. Morrey et al. concluded that the quality of the graft has a higher importance than the depth of biceps retraction in graft augmentation (38). Literature describes the usage of semitendinosus (40), quadriceps tendon (41), lacertus fibrosus (36) and fascia lata (42) as autografts and Achilles tendon (43), semitendinosus and tibialis anterior (44) as allografts with good outcomes; yet, if possible, a primary reinsertion is preferred (40).

The operative goal in complete distal biceps tendon rupture is to operate in earlier stages as complications and costs of operation are higher in later stages (45, 46, 47).

Conservative treatment

Non-surgical treatment most importantly consists of rest, nonsteroidal anti-inflammatory drugs (NSAIDs) and physiotherapy (16) for pain release and for regaining of strength (48). Additionally, cryotherapy (49), steroid injection, shockwaves (16, 50) or taping could be used, although some of them are questionable in usefulness (51).

Surgical treatment

Two approaches have been established over time: single-incision technique and double-incision technique. One doesn’t seem to be superior compared to the other (52).

During the single-incision technique, a transverse cut is made at or just distal to the antecubital fossa between the brachioradialis and pronator teres. Antebrachial cutaneous nerve and cephalic vein need to be identified and preserved. After mobilising the distal biceps tendon and freeing it from scar tissue, it can be fixated into the radial tuberosity (Fig. 4). The most common complication during this procedure is the injury to the posterior interosseous nerve (53).

Figure 4.

Single-incision technique: (A) debridement and preparation of the distal biceps tendon. (B) suturing fixation method (anchor) to distal biceps tendon (C) biceps tendon fixated to radial tuberosity.

First descriptions of the double-incision technique were made by Boyd and Anderson in the year 1961 (54). In the double-incision technique, one incision is made anteriorly transversely over the antecubital fossa and the second incision posterolaterally over the radial aspect of the ulnar border. After preparing the retracted biceps tendon, it is passed from the front to the back between pronator teres and brachioradialis. The fibres of the common extensor muscles are split and the tendon is retrieved between ulna and ancaneus and fixated to the radial tuberosity (52). This procedure reduces the risk of posterior interosseous nerve damage but increases the risk of heterotropic ossification and therefore reduces the range of motion (46). This is thought to be caused by a damage to the periosteum of the ulna mainly by detaching the ancaneus from the ulna. Morrey et al. proposed a modified version of the double-incision technique where the extensor carpi ulnaris or the extensor digitorum communis is split instead of detaching the ancaneus leading to reduced damage of the periosteum of the ulna (55).

Boyed and Anderson developed the double-incision technique in order to avoid difficulties and complications typical in the single-incision technique when approaching the radial tuberosity. More importantly, due to intraoperative rotation of the forearm, a more precise reinsertion of the distal biceps tendon into the radial tuberosity is possible (54). Forthman et al. described in 35% of cases an anatomical variation of the orientation of the radial tuberosity with a higher degree of pronation. Thus, a precise anatomical reinsertion via single-incision technique is not possible and therefore double-incision technique seems more promising due to the intraoperative rotation of the arm (56). Few studies, especially biomechanical cadaveric studies, support the double-incision technique due to the more precise reproduction of the anatomical footprint and orientation of the radial tuberosity (57, 58). Yet, it is not clear whether the advantage in more precise anatomical reinsertion, seen in double-incision technique, translates to a significantly better functional outcome as collateral musculature of the arm minimises the advantage in anatomical reinsertion (46, 52, 59, 60).

Overall, there is no clear evidence to choose one approach over the other as higher risks of nerve injuries appear in the single-incision technique and higher risk of heterotropic ossification appears in the double-incision technique. It is important to familiarise with the complication profile of each approach (46, 52, 59, 60).

The literature describes a hand full of fixation methods for the distal biceps tendon: cortical button, interference screw, suture anchors, bone tunnel and possibly intramedullary. Biomechanical studies showed that cortical buttons and cortical button–-interference screw combination had the best outcome in point of load to failure (32, 52, 61). Caekebeke et al., in 2020, suggest a new method of fixation, intramedullary fixation. These results were comparable with cortical button method but with less risk of posterior interosseous nerve injury (32, 62). These have promising results but still need further clinical evaluation. On the other hand, the clinical relevance is questionable as a clinical outcome is similar regardless of the fixation method (63).

Endoscopic repair of the distal biceps tendon has been successfully described in the literature but need more clinical evaluation (64). Thus far endoscopic usage has been mainly useful in debridement, partial rupture repair, retrieval of the retracted tendon in complete rupture and evaluation of the rupture (Fig. 5). In complete rupture, an open method is still preferred (32, 65, 66).

Figure 5.

(A) MRI in FABS position showing partial distal biceps tendon rupture. (B) Endoscopy showing same distal biceps tendon rupture. Copyright MoRe foundation.

Complications

The overall complication rate in distal biceps tendon repair is 25%, while minor and major complication rates made up 20.4% and 4.6%, respectively. The most common major complications are posterior interosseous nerve palsy (1.6%), re-rupture (1.4%), symptomatic heterotropic ossification (0.3%) and median nerve palsy (0.3%). Most common minor complications are lateral antebrachial cutaneous nerve palsy (9.2%), heterotropic ossification (3.7%) (Fig. 6), superficial radial nerve palsy (2.4%), infection (1.3%) and stiffness (1%) (46, 60). As mentioned before, there is no significant difference in complication rate between the single-incision technique and double-incision technique; the use of the single-incision technique has a higher risk of nerve palsy, while the double-incision technique has a higher risk of heterotropic ossification (46, 59, 60). Watson et al. suggest that cortical buttons and bone tunnels seem to have a lower complication rate compared to other fixation methods but further investigation is needed in order to draw conclusions (60). Controversially, Amarasooriya et al. suggest the cortical button with interference screw as fixation method with the lowest complication rate (1.8% major complication, 16.4% total) while cortical button alone has a higher complication rate (4.2% major complication, 32.8% total) (Table 2) (46). In case of very severe complications, a reoperation is indicated and accounts for 1% of distal biceps tendon operations (Table 3) (46). Different studies also show that the repair of chronic ruptures leads to a higher complication rate compared to acute ruptures, usually doubling in rate (47, 55).

Figure 6.

Lateral x-ray after anatomical reinsertion showing correct position of anchor and non-symptomatic heterotropic ossification.

Table 2.

Complications of incision technique and fixation method (57). Data are presented as percentages.

	Single incision	Double incision	Suture anchor	Cortical button	Interference screw	Button and screw	Bone tunnel
Major
PIN	1.5	1.5	1.7	3.3	2.9	0.9	1.7
Re-rupture	1.4	0.5	1.7	0.8	1.5	0.9	1.2
Symptomatic HO	0.0	1.0	0.0	0.0	0.0	0.0	1.4
Total	2.9	2.9	3.4	4.2	4.3	1.8	3.8
Minor
HO	3.6	5.8	5.4	6.1	5.8	1.5	4.9
LABCN	7.0	4.9	7.7	18.6	13.0	8.0	5.9
SRN	2.4	1.0	4.2	3.3	1.5	4.9	0.5
Total	13.0	11.6	17.3	28	20.3	14.5	11.3
Total	15.9	14.5	20.8	32.5	24.6	16.4	15.1

HO, heterotropic ossification; LABCN, lateral antebrachial cutaneous nerve; PIN, posterior interosseous nerve, SRN, superficial radial nerve.

Table 3.

Reasons of reoperation (57).

Reason	Per cent
Heterotropic ossification	43.8
Deep infection	9.4
Re-rupture	31.2
Nerve exploration	15.6

Rehabilitation

There are different rehabilitation protocols that are tailored to the patient. Generally, it consists of four phases. An acute recovery phase (6 weeks), where the patient mobilises joints that are not affected by the biceps with the application of cryotherapy. Later in the first phase, passive elbow flexion and extension are introduced. In the intermediate phase (weeks 6–12), isometric triceps exercises are introduced, while in the third phase, the advanced strengthening phase (weeks 12–16), isometric biceps exercises begin, followed by isotonic biceps movements. During the last phase, the focus is set on the return of the preferred movement (after 16 weeks) (67).

Outcome

Regardless of the incision technique and the fixation method, the rate of satisfaction is very high. Similar results appear in long-term follow-up examinations in flexion and supination in the range of motion and strength between the arm of the ruptured biceps and the contralateral arm. Huynh et al. showed slight weakness in flexion and supination with a maintained range of motion in a mean 3.7 years follow-up examination after surgery (Table 4) (68). Subjective questionnaires can be used to evaluate the personal satisfaction rate of the patient. Literature showed that the outcome of distal biceps tendon reinsertion in Arm, Shoulder and Hand score (DASH) and American Shoulder and Elbow Surgeons elbow score for pain/function (ASES-e) has been satisfying with a mean score of 7.4 and 4.5/33.6, respectively (68, 69).

Table 4.

Range of motion and strength of ruptured and non-ruptured tendon (86). The values are given as mean ± s.d.

	Ruptured tendon	Non-ruptured tendon
Range of motion (°)
Flexion	134 ± 11	134 ± 10
Supination	87 ± 9	88 ± 11
Strength (kg)
Flexion	25 ± 7	26 ± 9
Supination	168 ± 42	187 ± 34

Conclusion

Distal biceps tendon rupture is a relatively rare injury with many possibilities to diagnose and treat. It is important to familiarise with the complications profile in order to treat accordingly. The outcome of anatomical reinsertion gives in most cases very satisfactory results in objective measurements and subjective patient-rated self-evaluations.

ICMJE conflict of interest Statement

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding Statement

This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.