Trigger Finger

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What is trigger finger?

This is a very common hand condition. The flexor tendon can become irritated as it slides through the tendon sheath or tunnel. As it becomes more and more irritated, the tendon may thicken and nodules may form, making its passage through the tunnel more difficult. With advanced cases the tendon may become degenerate, roughened or “shredded”. If this occurs there is often marked grating and a fixed flexion deformity of the proximal inter-phalangeal (PIP) joint may develop.
The tendon sheath may also thicken, causing the opening of the tunnel to become smaller. We call this part of the tendon sheath the A1 pulley.

Symptoms

Patients may complain of a painful click at the base of the finger or thumb on the palm, which may lead to the finger being “stuck” in a flexed position at the PIP joint.

Swelling of the digit
Catching or popping sensation in the affected finger
Pain when bending or straightening the affected finger
Stiffness and catching tend to be worse after inactivity, such as when you wake in the morning. Your fingers will often loosen up as you move them.
Occasionally patients present with a “locked PIP joint”

Wolfe’s Classification of Trigger Finger

How Trigger Finger is classified:

Grade 1
Type: Pre-triggering
Pain in the palm; possible history of catching, but not seen on examination; tenderness over A1 pulley

Grade 2
Type: Active
Patient demonstrates catching but can actively extend the finger

Grade 3
Type: Passive
Patient demonstrates locking that requires passive extension (IIIa); may be unable to flex the finger (IIIb)

Grade 4
Type: Contracture
A locked trigger finger with a fixed flexion contracture of the proximal interphalangeal joint

What is the cause?

The cause of trigger finger is usually unknown. There are factors that put people at greater risk for developing it.

Trigger fingers are more common in women than men.
They occur most frequently in people who are between the ages of 40 and 60 years of age.
Trigger fingers are more common in people with certain medical problems, such as diabetes and rheumatoid arthritis.
Trigger fingers may occur after activities that strain the hand.

Examination

Often a painful nodule can be felt under the distal palmer crease, which moves when the finger moves.
Examine the extensor tendons on the dorsum of the hand. Ask the patient to make a full fist and ensure that the extensor tendons do not slip off the metacarpal head. This is called “pseudo-triggering” and can be caused by either an injury or chronic attrition and degeneration to the supports for the extensor tendon that keep it in the midline.

Look for signs of Dupuytren’s disease as this may sometimes cause triggering.

Differential Diagnosis

Pseudo-triggering. This is a problem of the MCP joint on the dorsum of the hand. The extensor tendons falls into the ulna sided gutter, causing the finger to lock. This is at the MCP joint and not the PIP Joint, and the pain is dorsally. This is an uncommon diagnosis but may present particularly in the elderly.
Triggering can also be a manifestation of flexor tendon sheath inflammation, especially in the Rheumatoid patient.

Dupuytren’s Disease – can cause triggering.

Investigations

In uncomplicated trigger finger no further investigations are required. It is always worth excluding diabetes and rheumatoid arthritis from the history by asking leading questions. Sometimes a fasting blood glucose or further serological tests may be required.

If there is a concern that there may be tenosynovitis, then an ultrasound scan can be helpful.

Treatment options

Here are the treatments available for trigger finger issues:

Non Surgical Treatment
If symptoms are mild, resting the finger or activity modification may be enough to resolve the problem.

Splinting the finger in extension at night can also be used in mild cases.
Steroid Injections (usually a long acting steroid such as Triamcinolone or methylprednisolone). This is usually injected into the tendon sheath. See injection section for advice on injection technique. A recent study found the total efficacy for steroid injections to be 66% (59/90). There was a 34% success rate with the first injection (31/90).
This rose to 63% (57/90) with the second injection and 66% (59/90) with the third injection. Clin Orthop Surg. 2012 December; 4(4): 263–268.

Most patients , if they are willing should have injection treatment initially. Exceptions include where there is a locked PIP joint where a fixed flexion deformity may develop if left untreated. Also certain cases where the flexor tendon is very roughened and there is marked grating or crepitus from the tendon, these cases may be better treated with surgical release and sometimes debridement of the flexor tendon.

Injections are less likely to provide permanent relief if you have had the triggering for a long time, or if you have an associated medical problem, like diabetes. In addition injections work less well if you have finger osteoarthritis as well as triggering.

When to Refer:

Failed conservative treatment with 1-2 injections
New onset triggering when previous trigger fingers have failed to respond to steroid injections and ultimately required surgery.
Patients with an underlying cause such as diabetes or renal disease are more likely to require surgery. Also see section on Diabetic Cheiroarthropathy.
Locked PIP joint or fixed flexion of PIP joint with triggering.

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