Distal Biceps Tendon Rupture

Original Editor - Matteo Ghezzi Top Contributors - Matteo Ghezzi, Khloud Shreif and Carina Therese Magtibay

Anatomy and Function

The biceps brachii muscle (biceps) is a powerful muscle of the arm composed of two heads. The long head originates from the supraglenoid tubercle of the scapula, while the short head arises from the coracoid process. The two heads converge to form a single, large muscle belly that inserts at the radial tuberosity. A fibrous membrane extending from the distal part of the muscle, known as the bicipital aponeurosis (or lacertus fibrosus), inserts into the deep fascia of the forearm.

Owing to its points of origin and insertion, the biceps brachii functions as a bi-articular muscle, participating in movements at both the shoulder and elbow joints. At the shoulder, the long head is involved in abduction and internal rotation, whilst the short head assists in adduction of the arm. Simultaneous contraction of both heads results in flexion of the arm.

In the elbow joint, the biceps brachii acts as a flexor, alongside the brachialis and brachioradialis, and serves as a supinator of the forearm, assisted by the supinator muscle. Maximum electromyographic activity of the biceps brachii occurs during simultaneous flexion and supination of the forearm.

Epidemiology and Risk Factors

The incidence of distal biceps tendon rupture (DBTR) is reported to be 2.55 per 100,000 patient-years. However, this figure is based on surgically treated patients, so the true incidence is likely higher. The vast majority of DBTRs occur in males aged 40 to 60, typically with an active lifestyle involving heavy lifting. Predisposing factors for tendon rupture include smoking, steroid use and increased body mass index (BMI) due to increased muscle mass or obesity. A higher BMI places additional load on tendons, while smoking restricts blood flow and impairs healing. Steroids weaken tendon structure by disrupting collagen synthesis.

Mechanism of Injury

The mechanism of injury originally described by Dobbie in 1941 was a “considerable extension force suddenly applied to a resisting, actively flexed forearm”. Over the years, this description has been refined to emphasize “an eccentric contraction that occurs during mid-flexion”. A common example is when an individual carries a heavy box with a flexed, supinated elbow. If the bag slips and an attempt is made to catch it, the sudden extension force may lead to an eccentric contraction, potentially causing a biceps tendon injury.

However, this mechanism of injury has recently been challenged. Video analysis of available footage distal biceps tendon ruptures revealed that the most common position at the time of injury was a supinated arm with full or near-full elbow extension (0° to 10° flexion). Furthermore, the predominant force at the time of rupture was isometric. Common activities leading to injury included deadlifting, biceps curls, lifting heavy objects, and arm wrestling.

Clinical Examination

Reverse Popeye Sign (Right Arm)

Common symptoms of a biceps tendon rupture include pain, ecchymosis and oedema around the antecubital fossa. A popping sound at the moment of rupture is often reported. Avulsion of the distal tendon results in weakness at the elbow, with reported decreases in elbow flexion and supination of up to 40% and 50%, respectively. Palpation of the attachment site on the radial tuberosity may elicit pain, and a palpable defect is often present. If the lacertus fibrosus is also torn, the biceps may retract proximally, resulting in what is known as a reverse Popeye sign.

Several clinical tests can confirm a complete distal biceps tendon rupture. The most commonly used tests include the hook test, the biceps squeeze test, the supination-pronation test, and the crease interval test.

Imaging

A thorough understanding of epidemiology, risk factors, mechanisms of injury, and a comprehensive clinical examination are usually sufficient to diagnose a distal biceps tendon rupture. However, if uncertainty remains, MRI or ultrasound can be employed to confirm the diagnosis, with MRI being more accurate than ultrasound (86.4% versus 45.5%), though ultrasound is more cost-effective.

Management

Surgical Management

Surgery is typically advised for young, physically active patients. If a distal biceps rupture is suspected, prompt referral to orthopaedics is recommended, with surgery ideally performed within 2 to 6 weeks. Delaying surgery increases the risk of muscle and tendon retraction, and dense scarring may form around the torn tendon. In some cases of significant delay, it may become impossible to reattach the tendon to the radius.

Conservative Management

Due to the loss of strength in flexion and supination associated with distal biceps tendon rupture, non-operative treatment is primarily recommended for elderly patients with low functional demands, and it has demonstrated acceptable functional outcomes. However, all patients who choose not to undergo surgery must be informed about the long-term implications of non-operative treatment on elbow and supination strength.

Rehabilitation

Following distal biceps tendon rupture, both post-surgical and conservative rehabilitation follow common strength and conditioning principles. In the UK, rehabilitation protocols vary among hospitals, and thus is important to follow the specific local protocol.

Following surgery, the elbow is typically placed in a protective bandage, and the patient is provided with a sling for comfort. Early active range of motion (AROM) exercises, including elbow flexion and extension and forearm pronation and supination, are generally encouraged between weeks 0 and 4 postoperatively. Patients are also instructed in scar massage techniques to prevent scar tethering and are advised to elevate the arm regularly to facilitate the reduction of swelling. Activities such as lifting, pulling, and pushing are strongly discouraged during this period to avoid complications.

At week 4 the patient should have full range of motion, and isometric strengthening exercises are implemented. Isometric elbow flexion is initially performed with the elbow in 90 flexion and supinated, using a percentage of maximum voluntary isometric contraction (MVIC) that the patient can tolerate. If the patient feels discomfort in the supinated position, neutral or pronated positions can be tried, as these reduce the involvement of the biceps and place more emphasis on the brachioradialis and brachialis muscles, respectively. The shoulder position can also be adjusted, with shoulder extension engaging the distal biceps less, while shoulder flexion increases its activation. Isometric elbow flexion near full extension should be avoided until the later stages of rehabilitation, as it mimics the mechanism of injury.

Commencing at week 6, isotonic biceps exercises are introduced. During the initial 2-4 weeks, these exercises are typically prescribed with high repetitions (e.g., 15-20) at low resistance. The number of repetitions is then gradually reduced while the load increased. The patient is expected to achieve full function and strength by the end of week 12. The principles of modifying forearm and shoulder positions, as discussed previously, remain applicable for the progression or regression of exercises.

Conservative management follows the same phases; however, it is important to note that by 12 weeks and beyond, strength in elbow flexion and supination will be approximately 40% and 50% lower, respectively, compared to the contralateral side.