The biceps muscle is one of the two major muscles in the arm responsible for elbow flexion. It runs from the shoulder region down the arm to attach to the radius forearm bone. In addition to enabling us to do curls, it supplies the majority of strength needed to rotate our palms up ("supinate" our forearms.) This supination strength allows us to do everyday tasks such as opening doors, unscrewing jars, or handling screwdrivers and similar handheld tools. As a result, rupture of the distal biceps tendon can be disabling for individuals who require upper extremity strength for vocational and recreational activities.
Distal biceps tendon rupture is most likely to occur in the dominant extremity of men between 40 and 60 years of age. While most reported cases of complete distal biceps tendon rupture have occured in men, women have been noted to have partial ruptures of the tendon. The rupture typically occurs at the tendon's insertion site on the forearm bone when an unexpected extension force is applied to the flexed arm. For instance, a water-skier might have their elbows flexed up while awaiting a water start, but if the boat revs up too fast it could overcome the resistance of the biceps tendon and lead to a rupture. Weight lifters commonly refer to this type of eccentric contracture as a "negative" biceps curl. In other cases, the rupture can occur in an area of preexisting tendon degeneration resulting from heavy labor or physical training.
The most common symptom associated with distal biceps tendon rupture is a sudden, sharp, painful tearing sensation in the antecubital region of the elbow (around the elbow crease.) The intense pain subsides in a few hours and is replaced by a dull ache, which can last for several weeks. Over time, this soreness can become chronic activity related pain. Weakness in elbow flexion and forearm supination will be more profound initially, but gradually diminish as the pain resolves.
On physical examination it is very important to compare injured to uninjured extremities. Assessment of any gross deformities, bruising, or palpable defect in the antecubital fossa region can be accentuated with active flexion of the elbow as the biceps muscle belly draws the detached tendon up the arm. Inability to palpate the distal biceps tendon in the antecubital fossa is indicative of a complete rupture.
Immediate surgical repair of the ruptured biceps tendon is advocated for optimal return of function. If diagnosed early (within four weeks,) these injuries are easily treated by anatomically reattaching the torn tendon back onto the bone. Failure to diagnose this injury or deciding not to surgically repair the tendon can lead to as much as fifty percent loss of flexion and supination strength in the arm. While this loss of strength may not be incapacitating for many activities of daily living, any jobs that require sustained strength and endurance (especially heavy laborers) can be severely limited.
