Distal biceps tendon rupture

Several risk factors contribute to the development of distal biceps tendon rupture. One such factor is the use of anabolic steroids, which have been associated with an increased risk of tendon injury. Smoking also plays an important role, with smokers at 7.5 times greater risk than non-smokers. Other risk factors include hypovascularization, characterized by reduced blood supply to the tendon, intrinsic degeneration and mechanical impingement due to limited space available for the tendon.

Its etiology involves a variety of factors. The main mechanism is the application of excessive eccentric tension on the tendon when the arm is forcibly moved from a flexed to an extended position. This sudden, powerful movement places the flexed elbow under significant stress, challenging its stability and potentially leading to rupture. Another contributing factor is the absence of an adequate blood supply, making it more vulnerable to injury. In addition, repetitive forearm pronosupination movements can cause abrasion and wear to the tendon, weakening it over time. Rarely, rupture of the distal biceps tendon may be associated with symptoms of median nerve compression, due to their proximity, which can lead to nerve compression or irritation, causing symptoms such as pain, numbness or weakness in the hand and forearm.

Clinically, patients often report feeling a painful snapping sensation after loading the elbow eccentrically from flexion to extension. The main symptoms associated with this injury are weakness and pain, mainly felt during supination. On physical examination, visual inspection and palpation are important, as there may be a variable degree of proximal retraction of the muscle body, leading to a change in muscle contour. Medial ecchymosis may also be present. A palpable tendon defect is often appreciated, indicating the absence of the biceps tendon at its usual site of attachment. Motor examination reveals specific patterns of strength loss: there is generally a greater loss of supination strength than flexion, with a 50% reduction in sustained supination strength, 40% in supination strength and 30% in flexion strength.

Provocation tests can be performed to assess tendon integrity. The hook test is commonly used, where the patient is asked to actively flex the elbow to 90° and fully supinate the forearm, the examiner then uses his index finger to hook the lateral edge of the biceps tendon. With an intact or partially torn tendon, the examiner can insert his finger about 1 cm below the tendon. However, false-positive results may occur in cases of partial tears, intact bicipital aponeurosis (a fibrous band attached to the biceps) or presence of the underlying brachialis tendon. Another test is the Ruland biceps squeeze test (equivalent to the Thompson test for Achilles tendon rupture), in which the elbow is held at 60-80° flexion with the forearm slightly pronated. One hand stabilizes the elbow, while the other grips the distal biceps. The test is positive in the absence of forearm or wrist supination. Despite the usefulness of these tests, the real challenge is to distinguish between complete and partial tears, as the tendon may be palpable in the case of partial rupture, leading to a similar clinical picture.

Radiological examination usually involves standard X-rays and magnetic resonance imaging. X-rays, although often normal, may reveal bony avulsion of the radial tuberosity, indicating an associated injury. Magnetic resonance imaging (MRI) plays a crucial role. To optimize its sensitivity, it is generally performed with the elbow in flexion, the shoulder in abduction and the forearm in supination, this positioning allowing better visualization and assessment of the tendon and surrounding structures. It is particularly important for distinguishing between complete and partial tendon tears. It can also differentiate between lesions involving the muscle body itself and those affecting the tendon. Finally, it is also useful for determining the degree of retraction of the tendon, this information being important for surgical planning, as greater retraction may require different repair or reconstruction techniques.

Surgery is generally recommended for people wishing to restore strength and function, especially younger patients with high physical demands or who participate in activities requiring competent muscle. It is also indicated in cases of partial rupture that do not respond to conservative treatment. Tendon repair or reconstruction aims to restore anatomical continuity to its insertion site on the radial tuberosity, enabling the tendon to gain in function. Various surgical techniques are available, including single- and double-incision approaches. The timing of surgical treatment is crucial, with surgery generally recommended within a few weeks of injury. Delaying surgery beyond this time can complicate the procedure and make simple primary repair impossible. In the case of sub-acute or chronic ruptures, a more extensive surgical approach may be required, allowing the retracted and healed tendon to be recovered, thus facilitating successful repair. These ruptures can also be successfully treated by direct repair, without the need for an allograft (transplanted tissue), however during surgery the elbow may need to be hyperflexed to achieve correct tendon fixation, and it is important to note that hyperflexion of the elbow does not result in loss of joint range or contracture. Surgical management generally leads to better functional results and a higher probability of restoring near-normal strength than conservative management.

Complications can arise, the most common being injury to the lateral antebrachial cutaneous nerve, with an incidence of around 9%. This complication is often associated with over-aggressive retraction during surgery, and is more frequent when a single-incision technique is used. Another possible nerve injury is to the posterior interosseous nerve, similarly more frequently observed with the single-incision technique, with an incidence of 1-2%. Both injuries usually resolve within 3 to 6 months. Superficial damage to the radial nerve is also possible, with an incidence of 2-3%. Heterotopic ossification (abnormal bone formation in soft tissue) can occur if the interosseous membrane and ulnar periosteum are disrupted during surgery. This complication is more often associated with the two-incision technique. Synostosis (fusion of adjacent bones) may also occur. Fractures of the proximal radius are also possible, particularly when large tunnels are created or when they are located close to the radial tuberosity. Finally, suture rupture is a potential complication of the bone tunnel method.