The tendon that connects your biceps muscle into your forearm inserts on a small prominence in upper part of your radius bone called the biceps tuberosity. Rupture of the distal biceps tendon is relatively common. The classic mechanism of injury is a sudden lengthening of the contracting muscle (eccentric force). This might be when catching a very heavy load or when doing heavy weights (e.g. biceps negative) in the gym. This rupture normally occurs at, or very close to it’s insertion into the radius bone, but occasionally the damage is near the muscle-tendon junction. The typical patient is an active male (rupture is very rare in ladies) in his 30s-50s. Many patients will have done lots of weight training in the past, or have a heavy manual job. The risk of rupture is increased in those who have used growth factor supplements to increase muscle gain (e.g. Deca or anabolic steroids) because these drugs allow the muscle to grow too quickly for the tendon to adapt.
Most patients feel a sudden pop or ripping sensation at the front of their elbow with immediate pain in their lower arm and upper forearm. It normally happens after lifting or dropping a heavy load. This pain is followed by swelling and bruising in the elbow crease and into the forearm. Patients report weakness in bending their elbow and in twisting their forearm. They often also notice an altered contour of the biceps muscle – the muscle belly will likely sit higher up in the arm (compare to opposite side). Also, patients sometimes notice that the biceps muscle belly will not move when they twist their forearm.
Photographs of the left and right arms of a 40 yr old man showing a retracted, chronic left distal biceps rupture
Yes, it is possible to rip off only part of the tendon. The injury mechanism is normally the same, but the deformity will not be present if there is only a partial rupture. If the symptoms remain severe, an MRI is useful in this situation to quantify the damage and plan management.
Most active working-aged patients will elect to have distal biceps repair surgery to restore optimum function if their tendon is fully torn, but it is not mandatory for every ruptured tendon to be repaired. As the biceps is a strong clockwise rotator of the right arm, right-handed patients with a right-sided injury tend to suffer more disability (e.g screwdrivers etc. are designed to be used clockwise in the right hand). If you have injured your left biceps and have a desk job you may do fine without surgery.
In a study assessing patients with distal biceps ruptures, those with un-repaired distal biceps ruptures had lost 30% of their flexion power and 45% of forearm outwards twisting (supination) torque. They also experienced cramping and loss of endurance in the injured arm. After repair approximately 95% of normal power in both movements is typically restored. If you have injured your non-dominant arm and have a low-demand job and lifestyle, you may manage well without surgery. If however, you have injured your dominant arm and engage in an active lifestyle, it is likely you will do better with surgery.
If you have a partial rupture of your tendon it is worth holding off with surgery to see how you recover as your tendon may heal. If you struggle to recover at three months, your tendon can still normally be repaired at that point