Rupture of the Extensor Pollicis Longus (EPL) tendon
What and where is the EPL tendon?
The tendon of EPL is located over the back of the wrist, where it bends through a tunnel, adjacent to a slight prominence of bone. This oblique direction is so that it can pull the thumb up and back, as if trying to “hitchhike”. Unfortunately, this arrangement makes the tendon prone to damage, from various causes, and then it can rupture. This is not generally very painful, but the thumb is then unable to extend actively.
Why does it rupture?
The most common cause of rupture is following a wrist fracture, of the end of the radius bone. This is an extremely common fracture in all age groups. The severity or displacement of the fracture is not indicative of the likelihood of EPL rupture, which is up to 1%. The rupture is probably due to bleeding and poor blood supply to the tendon in its tunnel, and often occurs weeks or months after the original injury.
Another cause of EPL rupture is rheumatoid arthritis. In that case, the damage to the tendon is both from the inflammation and damage to the joint beneath, and also direct tendon damage from the rheumatoid process, known as “teno-synovitis”.
What can be done?
In both cases, it is impossible to repair the tendon directly.
The best treatment is to move another tendon and join it on to the EPL tendon, this is known as “tendon transfer”. The tendon of “Extensor Indicis Proprius” (EIP) is used. The index finger has two extensor tendons that straighten it, and there is no demonstrable loss of function from moving one away. The tendon is always present.
What does the operation involve?
The operation can be done under local or general anaesthetic. A tourniquet (like a blood pressure cuff) is worn on the upper arm during the procedure to prevent bleeding.
Three small incisions are required: one (1cm) on the back of the index finger knuckle, one (2cm) on the back of the wrist, and one (3cm) on the back of the base of the thumb. The extensor indicis proprius tendon is divided next to the knuckle in the first incision, and then passed back to the wrist incision. It is then passed forward to the thumb incision. There, it is woven through the original thumb EPL tendon, taking care to ensure the correct tension.
The wounds are closed with a dissolveable suture, and a plaster of paris splint is applied to the palm side of the wrist and thumb.
What happens after the operation?
The operation is nearly always done as a “daycase”, with a hospital stay of just a few hours. The hand must be elevated, particularly for the next 48 hours.
After 10-14 days, the bandages will be removed, and our hand therapist will apply a new lightweight custom-made plastic splint to keep the thumb up, allowing the tendon transfer to heal without stretching.
Over the next four weeks, there is a carefully graduated exercise programme to allow increasing strengthening and movement, whilst protecting the woven tendon repair. The splint is normally discarded six weeks after the operation.
Are there any risks?
This is generally a very safe and effective procedure, with few problems. However, there are a few potential risks, as with any operation.
- Wound infections occur in less than 1% of cases, and usually quickly resolve with antibiotics.
- The scar may be tender. This is rarely significant, and usually improves with scar massage.
- The tendon transfer can become a little too loose, so that the thumb does not completely extend. This rarely causes a problem with function, and further treatment is not generally needed. Conversely, there can be some stiffness in achieving full flexion of the thumb into the palm. This usally improves with hand therapy, and again and further treatment is not generally needed. Grip strength can also take some months to return to normal.
- Numbness over the back of the thumb, caused by damage to a branch of the nerve.
- This rarely causes any functional problems, but there is often discomfort, and scar tenderness. This is treated with scar massage.
- Chronic Regional Pain Syndrome “CRPS”. This is a rare but serious complication, with no known cause or proven treatment. The nerves in the hand “over-react”, causing swelling, pain, discolouration and stiffness, which very slowly improve.
- Very rarely, the repair can pull apart completely, and need to be re-done.
- Any operation can have unforeseen consequences and leave a patient worse than before surgery. This is rare for EI to EPL tendon transfer.