Trigger finger (stenosing tenosynovitis) is a common condition that can affect any digit in the hand, including the thumb.
The most common symptom is clicking in the finger during flexion. Classically, the problem is worse on waking.
Sometimes the finger actually becomes trapped in a flexed position and the patient struggles to release it using the other hand.
Eventually the finger may click out – hence the analogy of pulling the trigger of a gun. Very often, the patient can feel a lump in the finger that seems to move at the level of the distal palmar crease.
Once one finger is affected, it is common for a second finger to be affected too. There is a strong association with other conditions (see box 1).
| Box 1 Associated conditions |
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Aetiology
The flexor tendons to each finger move through a series of loops, known as pulleys. These pulleys can be annular or cruciform and they are numbered in order beginning with the most proximal pulley.
The A1 pulley (the first annular pulley) is usually affected. The tendon becomes irritated and develops a fusiform swelling. This swollen area of tendon must slide through the A1 pulley whenever the finger moves and eventually it becomes too large for the space within the pulley. It is then possible for the lump to become trapped at one side of the pulley, effectively holding the finger in a fixed position.
The A1 pulley is at the level of the metacarpal head. It is also just distal to the distal palmar crease.
Treatment
Rest and NSAIDs are often tried first line. Some patients wear extension splints overnight to hold the finger straight while they sleep, preventing early morning clicking. However, very few patients choose this solution.
In clinic, the first treatment is an injection of steroid and local anaesthetic mixed in a 10ml syringe using a blue needle.
The tip of the needle needs to be close to the flexor tendon and the fluid injected within the flexor sheath. The steroid will then suppress inflammation in this region and tends to reduce the swelling on the tendon until it is sufficiently small to pass through the A1 pulley.
The injection can be unpleasant for patients, but at least half and up to three-quarters are cured.
It can take several weeks for steroids to act. I usually suggest that patients return after six weeks to discuss further options if the injection has not worked.
The first option is to do nothing, and as it is not life-threatening, some patients do choose to live with the problem.
Some surgeons perform a second injection and if that fails, proceed to surgery. Others suggest surgery next if the first injection fails.
Surgery for trigger finger is a simple day-case procedure
Surgery
Surgery is a simple day-case procedure. Although it carries the usual risks of surgical procedures, it is almost always successful.
The operation is usually performed under local anaesthetic, but could be done under general anaesthetic.
A tourniquet on the arm is used just above the elbow to achieve a near bloodless field. Many patients feel the tourniquet is the worst part of the procedure. Typically, the tourniquet would be on for five to 10 minutes.
A longitudinal incision is made over the A1 pulley area, the fat retracted and tendon exposed, ensuring the adjacent neurovascular structures are not over the tendon. Then a longitudinal incision is made over the A1 pulley and extended in either direction, until the tendon moves freely.
The lump in the tendon is usually a vague fusiform swelling, rather than the gritty isolated lump imagined from examining the patient.
Some surgeons use a transverse incision; this has the advantage that it can be extended to do two or more adjacent fingers in the same procedure.
Trigger thumb is slightly more difficult to operate on and a zigzag incision may be used to gain clear access to the flexor tendon and see the adjacent neurovascular structures before incising the tendon.
There is a theoretical risk of cutting the nerves at either side of the tendon. Patients need to be made aware that they could develop numbness on the side of the finger, should this complication arise.
It seems intuitive that the pulley is performing an important task and so there will be a problem with finger function after surgery. However, the A1 pulley seems to be one of those structures you can cut through without any functional deficit. Damage to the more distal pulleys would damage finger function and create bowstringing of the flexor tendons.
Dissolvable sutures are used to close and a bandage applied. The patient should wear a high arm sling most of the time for the first two days. The bandage comes off at day five and the adhesive dressing should be kept on for two weeks.
- Mr Cutts is consultant orthopaedic surgeon at the James Paget Hospital, Norfolk
