The long extensor tendon to the thumb is called the Extensor Pollicis Longus (EPL). This tendon straightens the end joint of the thumb and also helps pull the thumb in towards the index finger. The tendon runs around a bony prominence on the back of the wrist called Lister’s tubercle. In this area it is confined to a tight tunnel.
This tendon is vulnerable to rupture in the tunnel at the wrist. There are two situations that are associated with rupture. The first is after a fracture of the wrist, in particular where the fracture is not very displaced. The second is in Rheumatoid Arthritis where there is inflammation round the tendon in this area.
- There may be pain felt at the wrist but not always.
- Inability to straighten the end joint of the thumb easily.
- Inability to place the hand flat on the table and lift the thumb off the table.
Some patients may be able to feel a “ping” when the tendon ruptures. Many patients simply notice the thumb has an abnormal posture and isn’t working as it should be.
Investigations may include an x-ray of the wrist and hand. Ultrasound is often used to confirm the rupture.