What does the EPL do?
The extensor pollicis longus or EPL tendon pulls the thumb straight and opens the palm. It runs in an oblique direction in a tunnel around the bony prominence (Listers tubercle) at the back of the end of the radius bone. The EPL is responsible for extending the end joint of the thumb and permitting the thumb to lift off from a flat surface, a function called retropulsion.
Why might the tendon rupture?
The most common cause of a rupture is a fracture of the distal radius. which gives a sharp edge to the bone. (See Distal radial fracture).The EPL tendon lies directly on the bone as it passes around Lister’s tubercle, so that each time the thumb is moved it runs back and forward against a sharp edge causing damage to the tendon. It is a bit like pulling a rope over the edge of a saw – the tendon eventually frays and snaps. An EPL rupture can happen at any age, and is not related to the severity of the fracture.
Other causes of EPL rupture include: 1) Rheumatoid arthritis, where the tendon can rupture due to the chronic inflammation and joint damage seen in this condition. 2) Spontaneous rupture can be been after strenuous use of the tendon. 3) Attrition rupture can be caused by plates and screws put into the wrist by surgeons.
What are the symptoms and signs of EPL rupture?
Patients may experience some discomfort when the tendon is about to rupture. When the tendon does rupture, a “ping” may be felt. The thumb adopts a slightly abnormal posture and doesn’t function normally.
The problem most people have when the EPL tendon ruptures is inability to easily get the hand around things like a glass or a handle. The hand does not open well.
What happens if I do nothing? / What is the natural history?
Although having a rupture of the EPL tendon is a nuisance, many people do not find the loss of function terribly disabling, and manage to adapt. The tendon never heals or repairs itself because the ends tend to retract. Some people find that the tendon sticks down with scar tissue, and this can allow a trick movement to open the hand – When the wrist is flexed or bent the thumb extends, and when the wrist is extended the thumb flexes down – this is known as a tenodesis effect.
It is very safe to do nothing with an EPL rupture caused by a fracture of the radius – there is no long term risk other than the loss of function seen immediately.
If the rupture has been caused by arthritis or by the presence of plates and screws in the wrist, then there is an inherent risk of the same thing happening to other tendons, and the natural history is not usually benign.
What is the treatment?
In cases of EPL rupture following a distal radial fracture or spontaneous rupture, there is really only one good alternative to doing nothing that will maintain movement of the thumb joint; If you look closely at the anatomy picture at the top of the page, you will see that the index finger has 2 extensor tendons, but will work normally with just one. We take the second tendon, Extensor Indicis, and cut it at the base of the index finger. It can then be re-routed to the thumb and merged with the EPL tendon to make the thumb work again. This operation is usually called an Extensor Indicis to EPL transfer. After surgery, a plaster cast or splint is applied to keep the thumb in an extended position in order to protect the tendon transfer. This stays on for around 6 weeks, and is then removed to allow the hand to function.
This operation can be done at any time following this type of EPL rupture, as long as the thumb is kept supple.
Fusion of the inter-phalangeal joint of the thumb can be considered if tendon transfer is not suitable and if stability of the thumb is a problem. This has the disadvantage of not allowing movement at the thumb tip joint, but provides a strong and stable thumb.
Where there is another disease process responsible for the rupture of EPL, then the same operation can be done, but the underlying problem should also be addressed. This sometimes includes surgery to the underlying wrist joint, or removing any metal plates and screws from the wrist.
What are the risks to surgery?
The main risk specific to this operation is failure of the surgery to achieve the goal of active extension of the thumb. Although it is unusual to see complete failure, it is not unusual for people to be a bit disappointed by the result – the operation does not give back a normal tendon and the power is rarely as good as the normal tendon.
Other general risks are common to all operations, and you can read more about these here.
What is the outcome?
High level of patient satisfaction and improvement has been demonstrated in a recent audit of patients undergoing this procedure in NHS Fife.
© Fife Hand Service 2021