Overview
Trigger finger (and trigger thumb) is a type of flexor tenosynovitis. It is a relatively common disorder – with a lifetime risk of about 2.5%.
It is most common around the age of 40-60. Predisposing factors include:
- Type I diabetes
- Rheumatoid arthritis
- Gout
- Hypothyroidism
- Amyloidosis
The mechanism is thought to be related to abnormal tendon repair from the normal stresses and strains of use. Normal use causes small tears and minor damage to the tendons. As they repair, fibrosis can occur, along with oedema and swelling, which leads to the formation of hard nodules in the tendons. These hard nodules and then unable to freely slide through the normal fibrosseous tunnels (“pulleys”) that hold tendons down against the bones in the hand. The affected pulley is the A1 pulley. This causes a sensation of “popping” and “clicking” as these nodules squeeze through these tunnels, as indicated in the middle and right images below:
Presentation
- Finger that “locks’ into position when flexed
- Finger may appear to make suffer jerking movements when flexed and extended
- Can’t be extended, but can be manually extended with use of the other hand to pull the finger straight (only when severe).
- Tender firm nodule may be felt in the palm – at the level of the metacarpal head
- Thumb, 3rd and 4th fingers most commonly affected
Differential diagnosis
Dupuytren’s contracture
- May be tricky to differentiate from trigger finger. The following are features NOT typically seen in Dupuytren’sm but commonly seen in trigger finger:
- Tender nodule at the base of the finger
- Usually causing clicking or popping sensations when moving the finger
- Pain when moving the finger
- Symptoms often are worse after periods of inactivity – e.g. when first waking in the morning
Management
Conservative management
Is often first-line treatment for the thumb, and may be used in milder cases in fingers.
- Splinting – especially overnight
- NSAIDs
- Activity modification
The two main interventional options for management os corticosteroid injection and surgery. Surgery is not frequently required.
Corticosteroid injection is often used first-line for fingers
- Corticosteroid injection
- About 70% effective for complete resolution
- Injection into the palmar surface, with the finger extended, injection is made just distal to the nodule
- Palpate the tendon sheath during injection – you can usually feel the fluid entering the tendon sheath
- Encourage the patient to exercise the fingers for 1-2 minutes to spread the steroid along the tendon sheath
- Typically begins to work within 48 hours
- If it is not effective or recurs, a second injection may be attempted after 3 weeks (or more)
- Repeated failure of the procedure indicates need for surgery
- Surgery
- Release of the A1 pulley is performed
- May be first line in paediatric cases (rare)
References
- Trigger finger – orthobullets
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy