The injury typically occurs in men in their fifth decade but may also occur in athletes, especially those involved in contact sports. The cause may be different in these two groups with evidence of tendon degeneration in the non-athlete group.
How is this injury diagnosed?
The diagnosis of chronic distal biceps tendon rupture is made on clinical grounds by taking a detailed history and performing a physical examination. Typically the biceps muscle will be bunched in the upper part of the arm, the distance between the elbow crease and the biceps muscle with the elbow bent is increased, the biceps muscle does not move on passive rotation of the forearm and the patient will have a positive hook test.
In this test the shoulder is flexed forward to 90 degrees, the elbow is bent to 90 degrees and the hand is turned so that the palm is towards the face. The examiner can then attempt to hook their index finger underneath the tendon from the side. If the tendon is torn there will be not tendon to hook the finger under.
If there is doubt about the injury then an ultrasound scan may be helpful. Some surgeons prefer a magnetic resonance imaging (MRI) scan. This is best performed with the patient lying on their tummy (prone) with the shoulder flexed to 180 degrees and the elbow flexed to 90 degrees with the palm facing the top of the head (Flexion Abduction Supination (FABS) view).
Chronic distal biceps tendon tears can be left untreated if the individual is managing daily activities, occupation and hobbies without pain or weakness. Some people will notice that the arm feels weaker, especially for activities that require a strong twisting motion such as using a screwdriver. Others may experience a cramping type of pain in the biceps muscle. Many men simply do not like the appearance of the arm because this injury will typically cause bunching of the biceps muscle and a characteristic Popeye sign.
If the individual has symptoms these can be addressed by bridging the gap between the retracted biceps muscle and the radius bone. This can be done using a tendon tissue graft taken from the patient themselves (autograft) or from a tissue donor (allograft). Both techniques have advantages and disadvantages. The main advantage of the autograft is that there is no risk of transmission of infection from the donor to the patient, however it does mean having surgery at two sites in the body, as the graft is most commonly taken out of the leg, and this may be associated with complications. The graft from a tissue donor avoids this second site surgery but in theory there is a very small chance that infection could be transmitted from a donor to the patient. There are no descriptions of this ever having happened. The most commonly used donor tissue is achilles tendon graft (taken from the back of the heel of the donor).