Partial tear of the distal biceps tendon: Current concepts

Abstract

Background

Patients with partial rupture of the distal biceps tendon can present with vague elbow pain and weakness. Understanding of the anatomy and aetiology of this disease is essential to management. Patients can present with a single or multiple traumatic events or with a chronic degenerative history. On clinical examination, patients will have an intact tendon making the diagnosis more challenging. Clinicians, therefore, should have a high index of suspicion and should actively look for this pathology.

Objectives and Rationale

This review aims to discuss the current evidence in managing partial rupture of the distal biceps tendon with a suggested treatment algorithm.

Conclusion

Several clinical tests have been described in the literature including resisted hook test, biceps provocation test, and TILT sign. However, the diagnosis is usually confirmed by a magnetic resonance scan with the arm positioned in elbow flexion, shoulder abduction, and forearm supination and commonly known as FABS MR. Partial tendon tears that involve less than 50% of the tendon can be successfully managed conservatively. Tears that include more than 50% of the tendon are more likely to fail conservative management and would benefit from surgical intervention. It is crucial, however, to involve the patient in the decision making, which is based on their objectives and needs.

1. Introduction

Partial tears of the distal biceps brachii can be a challenging condition for the orthopaedic surgeon to manage. It was first described in 1987 and the incidence remains to be unknown, as it is often not diagnosed.¹

The diagnosis and management of distal biceps tendon (DBT) partial tears can prove to be difficult due to vague symptoms. Patients can suffer with weakness in flexion and supination with an intact distal biceps tendon. Our understanding, however, of this pathology is improving with new published literature showing better understanding of the anatomy, diagnosis, investigations, and management.

2. Anatomy

The biceps brachii muscle consists of two bellies that originate from the scapula proximally and inserts into the radius distally and is supplied by branches from the musculocutaneous nerve. The distal tendonous portion inserts into the posterior aspect of radial tuberosity.^2,3 The tendon was initially thought to be a single structure until 2007 when Esme et al. described the anatomy of the DBT in a cadaveric study.³ Esme et al. showed that both heads of the biceps tendon, long and short, to have distinct insertion into the posterior aspect of radial tuberosity. The short head, which lies more medial proximally, rotates anteriorly to the long head and inserts on the distal part of the radial tuberosity, distal to the long head, making it a stronger flexor of the elbow (Fig. 1). The long head lies deeper to and inserts proximal to the short head and further medially, away from the centre of rotation, giving it a greater lever arm for supination. Esme et al. divided the distal biceps anatomy into three zones from proximal to distal, shown in Table 1.

Fig. 1.

The anatomic footprint of the distal biceps tendon.

Table 1.

Shows the anatomical zones of the DBT from Esme et al. paper.³

Zone (Name)	Description
Zone 1 (Preaponeurosis)	The muscular portion of the distal biceps, proximal to the musculotendinous junction.
Zone 2 (Biceps aponeurosis)	Begins at the level of the musculotendinous junction and consists of three layers: 1. Superficial layer: originates from the anterior radial aspect of the long head of the biceps. 2. Middle layer: attached to the short head and acts as mesentery between the superficial and deep layers. 3. Deep layer: originates from the deep radial side of the musculotendinous area of the long head of the biceps.
Zone 3 (Tendinous)	The 2 tendons continuing past the lacertus fibrosus and inserting into the proximal radius.

The insertion of both tendons in the radial tuberosity is completely encircled by the bicipitoradial bursa, which can by injected with up to 10 mls of fluid. This bursa is important to identify for injection therapy and endoscopic procedures.⁴

The blood supply to the distal biceps tendon is categorised into proximal, middle, and distal zones (Fig. 2). The proximal zone consists of the proximal tendons and the musculotendinous junction, and is supplied by branches from the brachial artery. The distal zone is supplied by the posterior interosseous recurrent artery. The middle zone is hypovascular and depends on blood supply from the proximal and distal zones, making this zone a watershed area.⁵

Fig. 2.

The blood supply to the distal biceps tendon.

Ant.: Anterior, Post.: Posterior, Zone 1: Proximal zone, Zone 2: Middle zone and Zone 3: Distal zone.

3. Aetiology

The pathophysiology of partial DBT rupture is not understood. Two theories have been discussed in the literature, acute traumatic and chronic degenerative injury.⁶ The short head of DBT is more likely to be involved in traumatic tear whilst the long head is involved in 89% of atraumatic tears.⁷ The acute tear has a similar mechanism of injury to complete tendon tear, which occurs during sudden forced muscle eccentric contraction. The chronic degenerative tear is thought to be caused by a combination of tendon hypovascularity and friction between the tendon and the radial tuberosity.^5,8 When the forearm rotates, the space between the radius and ulna is narrowed, which could abrade or compress the biceps tendon during the repeated forearm rotation. This could be further complicated with the presence of a radial tuberosity hypertrophy or bony spur.⁸

Patrial tears are more likely to occur in older patients compared to complete tears, with the average reported age of 52 compared to 46 years, respectively.^9,10 Unlike complete tears, both female and male are likely to have partial tendon tears. Also, the association with obesity, smoking, or steroid use is not proven in partial DBT but is clearly shown in complete tears.¹⁰ The majority of cases reported in the literature show partial tears to involve the insertion of the tendon. Only one recent study reports 6 patients with partial tears in the musculotendinous junction and all the patients had an acute event leading to their injury.¹¹

4. Diagnosis

4.1. Clinical evaluation

The most common clinical presentation is pain in the antecubital fossa. Patients also suffer from weakness in flexion and supination strength, which is usually limited by pain.^12,13 These symptoms can precede a traumatic event in acute injuries, or it can have an insidious presentation such as in chronic injuries. Acute injury can present with oedema, and ecchymosis in the antecubital fossa, however, this is not always present, or it is less than expected than in complete tears due to the intact lacertus fibrosis, which may confine swelling and haematoma.13, 14, 15, 16

Clinical examination demonstrates tenderness at the DBT and pain with resisted flexion and supination. The tendon will be palpable with negative finding when performing the hook test, squeeze test, and supination-pronation test making it hard to differentiate between partial tears and tendinopathy.¹⁷

Provocative tests of partial DBT tears have only been described in the last 4 years. The TILT sign was the first to be described in 2018 by Shim et al.¹⁸ The test is positive by eliciting tenderness of the DBT at its insertion. This is performed by palpating posterolaterally over the radial tuberosity in the supination/pronation arc and it is positive when tenderness is illustrated in pronation.¹⁸ The resisted hook test, which is firstly described to assess integrity of the DBT after surgical repair, has also been described in the literature to assess partial DBT tears.^19,20 The most recent provocative test published in the literature in 2021 is the biceps provocation test (BPT) (also known as the Antwerp biceps test). Caekebeke et al. described the test in their study and suggest painful flexion from 70° of a pronated forearm compared to supination.²¹ The sensitivity and specificity of each test have been studied by Caekebeke et al.²² and the results are summarised in Table 2.

Table 2.

The sensitivity and accuracy of clinical test for DBT partial tear.

	Original paper18, 19, 20, 21		Caekebeke et al.22
Test	Sensitivity	Specificity	Sensitivity	Specificity
The TILT sign	100%	NA	58%	55%
The resisted hook test	100%	98%	78%	76%
Biceps provocation test	100%	100%	95%	97%
The resisted hook test + Biceps provocation test	NA	NA	98%	73%

NA: Not Available.

4.2. Investigations

The ideal investigation for DBT tears should be able to differentiate firstly between complete tear, partial tear, and other pathologies (e.g. tendonitis or bursitis) and secondly to evaluate the extent of the partial tear to aid with the management. Radiological modalities and endoscopy have both been described in the literature to aid with the diagnosis of partial DBT tears.

X-rays have a limited role in the diagnosis of partial DBT tear, but they can show radial tuberosity hypertrophy or osteophytes, which can be predisposing factors but not diagnostic features of a partial DBT tear.

Ultrasound (US) is a useful modality in diagnosing DPT tears and it is cheaper than Magnetic Resonance (MR). Dynamic US, performed in a range of pronation/supination and flexion extension, has the advantage of differentiating between complete and partial ruptures, with a reported diagnostic accuracy of 91%.²³ US can also easily compare to the other side if needed. It is, however, operator dependant and less reproducible. US for DBT is mainly performed on the volar aspect of the antecubital fossa and is less reliable at showing the entire tendon, particularly at its insertion. Occasionally, the insertion can be visualised by scanning the dorsal aspect of the forearm in pronation.

MR scan is considered the gold standard modality in diagnosing DBT tears, however, the sensitivity of conventional MR is lower in partial (59%) compared to complete tears (100%).²⁴ Some studies showed that US and MR have similar diagnostic accuracy in partial DBT tears and are as effective as each other at differentiating between complete and partial tears.²⁵ In 2004, Giuffre et al. described a specific MR for distal biceps which shows a longitudinal view of the DBT often in one section from zone 1 to zone 3²⁶. This MR is performed with the arm positioned in elbow flexion, shoulder abduction, and forearm supination and commonly known as FABS MR scan²⁶ (Fig. 3a, Fig. 3b). The FABS MR was initially thought to be better than conventional MR to diagnose partial DBT tears, however, the more recent literature does not support that.²⁷ The main advantages of the FABS MR are that it has improved inter-rater reliability and has significantly higher accuracy at grading the injury (the percentage of torn tendon) of partial DBT tears, which can be very useful in treatment planning.²⁷ MR scans also have the advantage of diagnosing other elbow pathologies which can aid in the diagnosis of non-specific elbow pain.²⁸

Fig. 3a.

Patient positioning for FABS MR.

Fig. 3b.

FABS MR clearly showing the distal biceps tendon.

Arrow pointing towards the distal biceps tendon.

DBT endoscopy is another modality that has been described in the literature. It was first described by Esme et al. and it was suggested that the direct visualization of the tendon is likely to be better than MR scan in quantifying the extent of the partial tear.⁴ However, there is no study yet to compare the accuracy of DBT endoscopy to MR scans. Endoscopy also has the risk of damage to neurovascular structures including the median nerve, brachial artery, lateral cutaneous nerve of the forearm, and recurrent radial vessels.⁴

Despite the lack of literature, there is a role for open exploration in patients with persistent symptoms. In our practise, we offer patients an open exploration and proceed procedure if the MR results are inconclusive and a trial of conservative management has failed. This will be a diagnostic and a therapeutic procedure at the same setting, as explained in the treatment section.

Based on the current literature FABS MR appears to be the safer and more effective modality in the diagnosis of partial DBT tears and estimating the extent of injury and, for this reason, FABS MR is the primary investigation in our practise and part of the management pathway (Fig. 4).

Fig. 4.

The management algorithm used by the senior author.

5. Management

The current evidence in the literature suggests the management of partial DBT tears is based on the extent of the tear with DBT tears. Tears which are less than 50% of the tendon can be managed conservatively. Surgical management is advocated for patients with more than 50% DBT or patients that failed conservative management.²⁹

5.1. Non-operative management

Despite a paucity of robust evidence to support the optimal treatment of partial distal biceps tears, conservative management is generally considered acceptable for older people and those with less physical functional demands.³⁰ After an initial indeterminate period of rest, physiotherapy is advocated by most authors.³¹ However, the specific rehabilitation strategies employed are poorly described and rarely validated. There is no consensus on the optimum timeframe for recovery rendering it difficult to advise patients about the success rate of non-operative management.³² A systematic review concluded that further research is necessary to establish an effective conservative management regime.³³

The largest case report found to date (n = 74), suggested 56% of patients initially managed conservatively ultimately went on to have surgery.³⁴ Reassuringly, the functional outcomes after surgery in this cohort were no worse if surgery was delayed compared to acute repair. However, the inability to perform manual labour or participate in sporting activities for several weeks or months could have important implications for the patient. A shared decision-making approach is proposed, setting realistic expectations with the patient. They should be educated regarding the potential for residual weakness, especially in supination, if the tendon is not repaired, allowing them to make an informed decision regarding their management.^35,36

The fundamental aim of physiotherapy treatment is to optimise tendon load capacity whilst minimising strain on the healing tendon.³⁷ Activity modification and load management advice is required. Cadaveric studies have failed to reach consensus on the exact load-to-failure angle at which the tendon is prone to rupture, but it is considered riskier in positions of increasing extension.^38,39 It is further postulated that a pronated forearm position not only stretches the tendon over the radial tubercle, but also narrows the inter-osseous space for the tendon to move within.¹⁷ Avoidance of repetitive terminal pronation activities could reduce impingement and further microtrauma to the tendon.

Partial distal biceps tears, especially in women, are considered part of the spectrum of tendinopathy.⁴⁰ Exercise is the primary management for any load induced tendinopathy. In the absence of an evidenced-based regime and prescriptive parameters, a multi-faceted programme tailored to the specific functional requirements of the patient is endorsed. This may include isometric, eccentric, or concentric exercises. It is also suggested that plyometric exercises are avoided until asymptomatic on provocation testing and resisted loading.⁴¹

Functional upper limb movement couples forearm supination with external rotation at the shoulder. In chronic partial distal biceps tears, even after surgical repair, persistent deficits in supination range, strength and endurance have been demonstrated.^39,42 This can lead to compensatory movement strategies more proximally, with patients developing secondary shoulder pain.³² Conversely, reduced scapular control and deficits in rotator cuff strength have been shown to increase loading at the elbow. The inclusion of shoulder girdle strengthening and control exercises may negate these issues. The sequential activation of the kinetic chain can also be employed using the lower quadrant and thorax, to optimise force transmission through the elbow.⁴³

Several authors report the use of steroid injections as part of their non-operative management of partial distal biceps tears. Peritendinous fluid, synovitis and bursitis have all been demonstrated on MRI alongside partial tears and could be a source of persistent pain and a target for injection.³³ However, the literature lacks any comparable evidence on the use of physiotherapy alone compared to physiotherapy combined with steroid injection. The current evidence also lacks consensus for the timing and indication for steroid injections. Based on the deleterious effect of corticosteroid demonstrated in other tendons, multiple injections of corticosteroid are not recommended for use in partial distal biceps tears.⁴⁴

Platelet-rich plasma (PRP) injection therapy is also being used by clinicians for the management of partial distal biceps rupture. The evidence in the literature is, however, limited with only two studies examining the role of US guided PRP injections in the management of distal biceps tendinopathy with promising results. Both studies had several limitations. Firstly both studies were cases series with a very small sample size (6 and 12 patients). Secondly, both were non comparative studies, and thirdly both studies focused mainly on tendinopathy and not partial DBT tears. Partial tears were included as a part of tendinopathy spectrum, Barker et al. had 1 DBT partial tear, out of 6, and Sanli et al. had 8 DBT tears out of the 12 patients in their cohort. For those reason, the outcomes of PRP injections in partial DBT tears are still poorly understood, especially for acute injuries. A large comparative randomised study is required to confirm the benefit of PRP in partial DBT tears.^45,46

5.2. Surgical management

The primary objective of surgery in DBT tears is to improve pain and preserve functional forearm rotation. The outcomes from surgery with complete DBT tears are comprehensively documented in the literature and are shown to improve flexion and supination power. The outcomes from surgery for partial DBT tears are less investigated and a systematic review by Behun et al. published in 2016 had only level 4 and level 5 evidence with 11 case reports and 8 case-series with a total of 84 patients.³³ The limited evidence in the literature shows good outcomes following surgery with 94% of patients reporting satisfactory outcomes. The majority of those patients (75%) underwent surgical intervention following failure of conservative management.³³ Robbrecht et al. shows similar outcomes following surgical repair for partial tears or complete tears, with similar range of movement and power of flexion and supination in both groups (when female patients were excluded from the partial DBT group).⁹ Bauer et al., showed that patients with >50% tear who had conservative management are 3 times more likely to undergo surgery, and there was no difference in the outcomes between early and delayed surgery.³⁴ Another finding from this study was that high demand patients were significantly more satisfied with outcomes from surgery compared to low demand patients. Tomizuka Y et al. showed, in a cadaveric study, that there is significant loss of supination with partial tears that are >75%.³⁶ The current consensus is to treat partial tears that involve more than 50% of the tendon surgically with debridement and repair with or without releasing the tendon completely.^29,47,48 It is important to note that in the systematic review by Behun et al. nearly a third of the patients with >50% tear had successful conservative management.³⁴ All the information above from the published literature emphasises the importance of a shared decision making between the clinician and the patient, taking into account the patient's age, occupation, hand dominance, and activity level.

The surgical techniques used for partial DBT tears, including approaches and type of repair, are the same as described for complete tears. The approaches included a single anterior incision, a single posterior incision, or a two-incision technique. Each approach had advantages and disadvantages with no conclusion in the literature to decide which is best for DBT Repair. The methods of fixation that have been described in the literature included using suture anchors, cortical endobutton repair, and trans-osseous repair.²⁹ All types of repairs had a satisfaction rate over 90% and a good power of supination and flexion of the elbow.^{13,15,29,33,35,}47, 48, 49 Only one comparative study comparing suture anchor repair to the endobutton repair in partial DBT rupture showed a significantly higher re-rupture rate with the use of suture anchors.⁴⁹ The main confounding factor of this study was that in the suture anchor group the authors kept the intact portion of the tendon compared to full detachment in the endobutton group. Some of the studies have described a full release of the tendon with debridement and followed by repair with one of the methods above. Other studies suggested protecting the intact part of the tendon and using suture anchor technique to repair the injury section. There are no studies to compare the two techniques.

Debridement of the tendon and bursa is also advocated in patients with <50% tear with persistent pain and weakness despite conservative management. This can be performed with open technique or endoscopically. In our practise, patients with a partial DBT <50% or non-conclusive MR scan would undergo an open exploration and management algorithms shown in Fig. 1. Esme et al. and Caekebeke et al. both described techniques in DBT endoscopy with introducing an arthroscopy scope into the bicipitoradial bursa. Both articles commented on the safety of the procedure and how accurately it can be in diagnosing the extent of the tear.⁴ Vandenberghe and Van Riet described an algorithm for endoscopic management of partial DBT tear shown in Table 3. The outcomes from endoscopic debridement are not published yet, therefore, this procedure is yet to be used in our clinical practise.⁵⁰

Table 3.

Surgical algorithms of DBT endoscopy suggested by Vandenberghe and Van Riet.⁵⁰

Tear percentage	Management
Less than 25%	Debridement of the tear
25–50%	The tear is debrided and the tendon is reinserted using a bone anchor
>50%	The tendon is detached fully, the stump is debrided, and repair is performed using cortical endobutton

Complications following surgery were the primary reason for patients reporting surgical outcomes as unsatisfactory. Behun et al. has shown that the complication rate was 28%, with lateral antebrachial cutaneous nerve paraesthesia (17%), posterior interosseous nerve palsy (6%), elbow discomfort (2%), revision surgery (2%), and asymptomatic heterotopic ossification (1%) reported.³³ This is similar to the 37% reported complications following surgery for complete DBT tear as reported by Cains et al.⁵¹

5.2.1. Post-operative rehabilitation

Within the limited research that has been published regarding operative management, there is no standardised protocol for post-operative rehabilitation of partial distal biceps tears. Although protocols provide a good guideline, post-operative rehabilitation should be tailored to the individual, taking into consideration the severity of their injury, their tendon health and the stability of fixation achieved intra-operatively.⁵² Communication between the surgeon and therapist is essential, with slower progression through a milestone-based protocol advocated when there are concerns over the security of surgical repair.

Use of a cortical button has been shown to provide superior fixation, enabling accelerated rehabilitation with immediate post-operative mobilisation.^49,53 Table 4 illustrates the post-operative rehabilitation guidelines for surgical repair of the distal biceps tendon using a cortical button, from the specialist physiotherapist author's unit.

Table 4.

Post-operative rehabilitation guidelines for surgical repair of the distal biceps tendon using a cortical button, from the specialist physiotherapist author's unit.

	Goal	Rehabilitation
Acute Stage 1–2 Weeks	-Preserve integrity of Repair -Optimise Tissue Healing -Reduction of pain & swelling -Prevent negative effects of immobilisation	-Sling used for pain relief and to prevent arm being forced into risk positions -Active elbow range of motion exercises in supine with 90° shoulder flexion with no end range stretching -Shoulder exercises maintaining elbow flexion -Kinetic chain activation exercises
Intermediate Stage 2–6 Weeks	-Restoration of functional range of movement -Preserve integrity of Repair	-Wean from sling -Active elbow range of motion exercises to point of mild stretch (no overpressure) -Soft tissue/joint manual mobilisation if any restriction -Progress shoulder & kinetic chain exercises
Late Stage 6–12 Weeks	-Optimise function specific strength, power & endurance -Return to full work and recreational activities	-Commence stretching exercises if full range not regained by 6 weeks -Introduce light resistance from 6 weeks (<2Kg/5lb) -Resistance only to be increased as pain and control allows -Once flexion & supination strength comparable to opposite side, commence function specific strengthening and endurance exercises incorporating whole kinetic chain

*Timescales are a guideline only and progression through the stages should be based on pain levels, neuromuscular control and patient compliance. A period of immobilisation may be necessary in cases of poor tissue quality. Timescales may also be delayed where the surgeon has concerns over tension or fixation security intra-operatively.

6. Conclusion

Partial distal biceps tears can be a challenging injury to diagnose and manage, but our understanding of this pathology has improved in the last two decades. Although, MR and US are as effective in the diagnosis of partial DBT tears, the extent of injury is best diagnosed with FABS MR scan or endoscopy. Conservative management can have good outcomes when the tear involves less than 50% of the tendon. Surgical management has preferable outcomes in young, active patients with more than 50% tear or patients that failed conservative management. The management of this injury should be strictly based on a shared decision approach between the patient and clinician.

Funding/sponsorship

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Institutional ethical committee approval (for all human studies)

Review article with no human participants.

Author's contribution

Zaid Hamoodi: Conceptualization; Formal analysis; Methodology; Visualization; Roles/Writing – original draft; Writing – review & editing.

Joanna Winton: Conceptualization; Formal analysis; Methodology; Roles/Writing – original draft; Writing – review & editing.

Vijaya Bhalaik: Conceptualization; Formal analysis; Methodology; Supervision; Writing – original draft; Writing – review & editing.

All authors made substantial contributions to research and writing of the paper and have read and approved of the submitted and final version.

Declaration of competing interest

None.