Introduction

Trigger finger (flexor tenosynovitis or stenosing tenosynovitis) is when a finger locks in a flexed position and struggles to extend fully. Narrowing of the flexor tendon sheath restricts finger movement. This can cause the finger to snap straight suddenly or need help to open. The most affected fingers are the ring finger and the thumb of the dominant hand. On movement, trigger finger can cause pain and discomfort in the palm.¹

Trigger finger is a common condition, affecting 2.6% of the general population. It affects women more than men and is most seen in adults in their 50s and 60s. Although uncommon, in children, it occurs before the age of 8.²

Background

The flexor tendons of the fingers pass through a tubular structure called the sheath. Bands of tissues known as pulleys along the sheath hold the flexor tendons to the finger bones. The pulley at the metacarpophalangeal joint, called the A1 pulley, is mostly involved in trigger finger. It can also affect A2 (proximal interphalangeal joint) or A3 ( distal interphalangeal joint).¹

Continuous use of fingers causes inflammation and nodular formation of the flexor tendon, and narrowing of the A1 pulley sheath. This restricts the smooth movement of the tendon through the A1 pulley sheath and results in pain, clicking, catching and locking of the affected finger.⁴ Patients experience locking of fingers on both extension and flexion.¹  

Causes

The exact cause of trigger finger is not fully known, but some factors are thought to contribute. In adults, repetitive hand movements, especially in specific jobs, can lead to trigger finger. Inflammatory conditions such as rheumatoid arthritis and gout, and metabolic conditions like diabetes and thyroid diseases, can increase the risk of development, with 10% of people with diabetes developing trigger finger at some point.³

Structural defects, such as abnormal attachment of specific muscles (lumbrical) to the A1 pulley, can lead to trigger finger.¹ Diseases such as amyloidosis and carpal tunnel syndrome can also cause structural changes, leading to trigger finger.

Developmental issues in the flexor tendon and sheath size can cause trigger finger in children. Metabolic diseases (Hurler syndrome) and inflammatory conditions (Juvenile Rheumatoid Arthritis) can increase the chances of trigger finger development.¹

Treatment

Treatment options for trigger finger range from conservative treatment to surgical procedures.¹ Conservative treatment like rest, medications (NSAIDs- non-steroidal anti-inflammatory drugs), and splinting can help manage mild symptoms. If symptoms are severe, corticosteroid injections and surgery can be used to manage trigger finger.

Non-surgical treatments

Rest and activity modification 

To reduce repetitive finger movement, pain and inflammation.

Splinting  

Splinting restricts finger movement and can reduce symptoms like pain and inflammation of

the tendon and sheath. It is usually done as an alternative to corticosteroid injection.⁵ Splinting the joint at the base of the finger (metacarpophalangeal) for 6-10 weeks is commonly used. In some cases, splinting the finger's middle joint (proximal interphalangeal joint) during nighttime can provide additional benefits for patients who experience locking in the morning.⁵ However, for patients with chronic and severe symptoms, splinting may be less effective.¹

Medications

Both Topical and oral NSAIDs are used for pain and inflammation relief. Oral NSAIDs commonly used are diclofenac, ibuprofen, naproxen, celecoxib and etoricoxib. The most common topical NSAIDs are ketoprofen and diclofenac.⁴

Corticosteroid injections                                                                                                                  

Corticosteroids are one of the first-line treatments for trigger finger and have many advantages and drawbacks (see below). They are injected into the tendon sheath and reduce pain and inflammation. Corticosteroids are often ultrasound-guided as they give better results and faster recovery¹. Patients usually experience relief after a single dose; however, symptom recurrence is common. Corticosteroids cannot be given to all patients, especially those with chronic conditions like diabetes and those with multiple fingers involved. This is because it is more challenging to treat the symptoms in those individuals.

Advantages¹

• Easy to administer
• Cost effective
• Minimalcomplications
• Minimally invasive

Adverse effects - very rare¹

• Breakdown of Tissues
• Colour changes of the skin 
• Infection
• Tendon rupture/ tear

Extracorporeal sShock wave therapy (ESWT)²

ESWT is a new orthopaedic treatment and an alternative to corticosteroid injection. Shockwaves are delivered to affected tendons, stimulating the body's natural healing process.

Surgical treatment 

Surgery is a highly successful treatment for trigger finger.

Indications¹

1. No relief with splinting and corticosteroid injection
2. Failed treatment of locked trigger finger
3. Trigger thumb in infants

The surgical treatment of trigger finger involves releasing the A1 pulley.. The tendons are left intact so that finger movement can return to normal. Surgery can be either open, percutaneous or endoscopic. ³

Percutaneous release³

This procedure has a high success rate (87%), does not cut the skin and has a short recovery period. However, it requires a deep knowledge of the affected finger’s structure. These structures are not visible during the procedure, and there is a risk of incomplete release of the pulley, damage to the nerves, vessels,  tendons and the joint capsule. 

Open surgical release³

The A1 pulley is released through a cut in the finger, where the affected structures can be seen, which can reduce nerve, vessel and tendon damage. The open surgical release increases the risk of infection of the operated area, pain and scarring. This procedure is used in patients at risk of developing complex functional issues, such as those with chronic health conditions (diabetes, rheumatoid arthritis).

Endoscopic surgery ³

Endoscopic surgery uses a small camera to visualise the affected structure (A1 pulley) through a small finger cut. Although more expensive than other surgical methods, it is easier to perform with a shorter recovery and fewer complications.

Post-surgical rehabilitation

Subsequent splint and physiotherapy of the hand are required to restore the function.

FAQs

Why is it called a trigger finger?

The trigger finger gets its name from the painful popping or clicking sound produced when the locked digit moves.

What kind of imaging technique can diagnose trigger finger?

Ultrasound is a commonly used imaging technique to diagnose trigger finger. It allows both static (still) and dynamic (movement) examination of the trigger finger and provides comparison with the other fingers. An X-ray can help to rule out other conditions, such as a broken finger. 

How is diabetes related to trigger finger?

Diabetes increases the risk of trigger finger (10%) compared to the general population (2.6%). The risk is not directly related to blood sugar control, but diabetes can cause inflammation and thickening of the finger's tendons.

Is trigger finger a type of arthritis?

 No, trigger finger is not a type of arthritis. Arthritis causes joint inflammation, whereas trigger finger causes tendon or tendon sheath inflammation.

Summary

Trigger finger is usually diagnosed based on clinical presentation and physical examination. The first line of treatment includes rest, activity modification, splinting and corticosteroid injection. More chronic and severe cases can be treated with surgery, which is the final treatment for trigger finger.