Trigger Thumb (Pediatric)

Pediatric trigger thumb is a stenosing tenosynovitis of the flexor pollicis longus (FPL) tendon at the A1 pulley level. Despite often being called "congenital trigger thumb," it is not truly congenital - it is rarely present at birth and is thought to be acquired in early infancy.

Key epidemiological points:

• Incidence: 0.3-0.5% of children (approximately 3 per 1000)
• Age at presentation: Typically noticed between 6 months and 3 years
• Bilaterality: 25-30% of cases are bilateral - always examine both thumbs
• Sex distribution: Equal male to female ratio
• Association: No strong association with other congenital hand anomalies

Theories of pathogenesis:

1. Size mismatch theory: FPL tendon grows faster than A1 pulley, causing stenosis
2. Repetitive microtrauma: Thumb sucking or gripping patterns
3. Intrinsic tendon abnormality: Primary FPL nodule formation

Thumb pulley system: The thumb has a unique pulley system compared to the fingers:

Pathophysiology of Notta's Node:

The characteristic finding is Notta's node - a palpable nodule of the FPL tendon at the A1 pulley level.

Anatomical considerations for surgery:

Key anatomical relationships:

• A1 pulley lies at the MCP joint crease
• FPL tendon passes through the A1 pulley
• Radial digital nerve crosses palmar to A1 pulley (at risk)
• Ulnar digital nerve is more protected (dorsal position)
• Sesamoids lie deep to the A1 pulley

Typical presentation:

Parents typically present with concerns about:

• "My child's thumb is always bent"
• "The thumb makes a clicking sound"
• "Unable to straighten the thumb"
• "Pain when moving the thumb" (less common)

Clinical examination findings:

Essential examination steps:

1. Inspection: Fixed flexion of the IP joint (typically 25-30 degrees)
2. Palpation: Notta's node at the MCP crease - feels like a small pea
3. Active extension: Unable to actively extend the IP joint
4. Passive extension: May be possible with a palpable/audible click
5. Contralateral thumb: Always examine for bilateral involvement

Red flags requiring further investigation:

• Multiple digit involvement (suggests syndromic condition)
• Associated hand anomalies
• Neurological signs
• Family history of connective tissue disorders
• Failure to respond to expected treatment

Investigations are rarely required in straightforward pediatric trigger thumb.

Role of imaging:

When to investigate:

• Trauma history (exclude phalanx fracture)
• Bony abnormality suspected
• Atypical presentation
• Multiple digit involvement
• Failed surgical release (evaluate for incomplete release)

📊 Management Algorithm

Click to expand

Management overview:

The key management decision is observation vs surgical release, primarily determined by age and duration of symptoms.

Factors favoring earlier surgery:

• Fixed flexion contracture greater than 30 degrees
• Bilateral involvement (combine procedures)
• Parent occupational/logistical factors
• Progressing contracture despite observation

Incomplete release:

• Recognized by persistent triggering post-operatively
• Usually due to incomplete A1 pulley division
• Treatment: re-exploration and complete release

Prognosis by management:

Long-term outcomes:

• No functional deficit after successful treatment
• Normal thumb strength and range of motion
• Minimal scarring with proper technique
• Return to normal activities within 2-3 weeks

Epidemiology and presentation:

Pediatric trigger thumb is commonly seen in Australian pediatric orthopaedic and hand surgery practices, with an incidence consistent with international data (approximately 0.3-0.5% of children). Most cases present through GP referral or maternal-child health screening, with parents noticing the fixed thumb flexion deformity between 6 months and 3 years of age. Aboriginal and Torres Strait Islander children have similar incidence rates to the general population.

Healthcare delivery and practice patterns:

Most Australian pediatric orthopaedic centers follow an observation-first approach for children under 3 years, consistent with international best practice. This reflects both the high spontaneous resolution rate and the preference to minimize surgical interventions in young children. Public hospital waiting times for elective pediatric hand surgery typically range from 3-6 months, which paradoxically may benefit younger children by providing additional observation time for potential spontaneous resolution. Private centers often have shorter waiting times, allowing earlier surgical intervention if families prefer definitive treatment over observation.

Surgical management considerations:

A1 pulley release is performed as a day surgery procedure under general anaesthesia in both public and private settings. Most centers in major cities (Sydney, Melbourne, Brisbane) have pediatric-trained hand surgeons or pediatric orthopaedic surgeons with hand surgery expertise. Regional centers may have longer waiting times or require travel to metropolitan facilities. Bilateral cases are commonly addressed in a single surgical session to minimize anaesthetic exposure and reduce disruption to families, particularly those from rural and remote areas.

Parent education and cultural considerations:

Australian families generally have good health literacy and appreciate evidence-based counseling about spontaneous resolution rates. Parent information resources emphasize that trigger thumb is not caused by anything the parents did and that observation is a valid and recommended approach for younger children. Cultural considerations for Indigenous families may include acknowledgment of distances required for surgical intervention and coordination with Aboriginal health workers for follow-up care in remote communities.