The biceps muscle, is a muscle of the upper arm which is important for elbow bending (flexion) and more importantly turning the palm up (supination). It has two tendons close to the shoulder (proximal) and one tendon at the elbow (distal biceps tendon). Sometimes, the distal biceps tendon can rupture, either completely or partially. This usually occurs in middle aged men, who have done a lot of heavy lifting in the past.
The distal biceps tendon usually ruptures suddenly when it is being strained, i.e. when something heavy is being carried. When it ruptures, the patient usually feels a snap or pop, followed by pain. There can be a variable amount of swelling. Over the next few days, bruising usually develops in the lower forearm.
If a clinician is suspicious that a patient has had a rupture of the distal biceps tendon, there are a number of clinical signs (s)he can look for:
- Proximal Retraction of the muscle belly: (Figure) When the elbow is flexed against resistance, the biceps muscle belly contracts and moves up the upper arm to the shoulder. This can be easily detected by comparing one arm to the other.
- Absent Distal Biceps Tendon: The distal biceps tendon is a cord like structure that is easily palpable in the front of the elbow (flexion crease). If it is ruptured, it usually retracts up the arm and is no longer palpable at the front of the elbow. Once again, comparing one side with the other is important. Sometimes, the bicipital aponeurosis, which is another part of the biceps muscle, can remain intact and can confuse the picture.
- Weakness of Supination: This is the most sensitive clinical sign by far. With the elbow held at a right angle, the biceps muscle is an important muscle for turning the palm up (supination). If it is ruptured there will be weakness of supination when comparing the ruptured side with the intact side. With a partial tear the patient will have alot of pain and weakness when performing this test.
If the diagnosis is suspected, further information can be attained by imaging the tendon with an ultrasound or MRI, however these investigations can often be misleading and therefore assessment by a physician experienced in managing elbow disorders is important.
A ruptured distal biceps tendon can be managed non-operatively, or with an operation to repair the tendon. If the rupture is managed non-operatively, the patient must expect to lose at least 40 - 50% of the power of supination. In addition there will be a cosmetic difference between the upper arms. The advantage of an operation is that if successful it will restore most of the power of supination, and will improve the cosmesis of the limb. These benefits must be weighed against the risks of any operation.
If the decision is made to manage the ruptured distal biceps tendon with an operation, then the sooner the operation occurs the greater the chance of success as the technical difficulty of the operation increases as the weeks pass. It is important for patients to be aware that it is not uncommon for them to experience post-operative numbness on the outer aspect of the forearm. This is usually only a temporary side effect, and is due to bruising of a nerve as the muscle is brought out to length. After the operation, the patient wears a sling only for comfort, and can begin actively moving the elbow immediately. (S)He must not carry anything over 1 kg in the effected limb for the first 6 weeks, and must protect the repair for at least another 3 months.