What is the likely diagnosis for a 1‑ to 4‑year‑old child with acute elbow pain and limited use after a forearm pull?

Diagnosis: Radial Head Subluxation (Nursemaid's Elbow)

The likely diagnosis for a 1- to 4-year-old child presenting with acute elbow pain and limited arm use following a forearm pull is radial head subluxation, commonly known as "nursemaid's elbow" or "pulled elbow." This is the most common upper extremity injury in children under 6 years presenting to emergency departments 1, 2.

Clinical Presentation

The classic presentation includes:

• Mechanism: Sudden longitudinal traction on an extended, pronated arm (occurs in 55% of cases, though absence doesn't exclude diagnosis) 2
• Age: Typically 1-4 years old (mean age 27 months), though rare cases occur in infants as young as 6 months 2, 3
• Symptoms:
  • Immediate refusal to use the affected arm
  • Arm held in pronated, slightly flexed position at the side
  • Pain localized to the elbow region
  • Decreased arm movement
  • Absence of swelling (key distinguishing feature from fracture) 2
  • No point tenderness (unlike fractures) 2

Pathophysiology

The injury occurs when sudden traction causes the radial head to slip through the annular ligament at its narrowest diameter, with interposition of the anterior joint capsule between the radial head and capitellum 4. This mechanism is unique to young children due to their incompletely developed radial head and relatively lax annular ligament.

Diagnostic Approach

Clinical Diagnosis

Radial head subluxation is primarily a clinical diagnosis based on:

• Characteristic history of pulling mechanism
• Typical age group (1-4 years)
• Classic presentation with arm held pronated and immobile
• Absence of swelling or point tenderness
• Normal neurovascular examination

Imaging Considerations

Radiographs are typically NOT necessary if the clinical presentation is classic 4. However, obtain radiographs if:

• Mechanism is unclear or inconsistent with pulled elbow
• Point tenderness or swelling present (suggests fracture) 2
• Child is under 6 months old (consider infection or neurologic causes) 2
• Failed reduction attempt
• Any concern for fracture or other pathology

Important caveat: Radiographs in pulled elbow are notoriously difficult to interpret, often showing oblique pronated views that appear normal 4. The ACR guidelines emphasize that radiography is the initial imaging for acute elbow pain when fracture is suspected 5, but in classic pulled elbow presentations, clinical diagnosis suffices.

Point-of-Care Ultrasound (Emerging Tool)

Recent evidence suggests POCUS may aid diagnosis by identifying:

• "Hook sign" or "J-sign" (displaced annular ligament)
• Absence of elbow effusion (effusion suggests fracture requiring X-ray) 6

However, this remains an adjunctive tool and is not required for diagnosis or management.

Differential Diagnosis

Key conditions to exclude:

1. Fractures (22% of upper extremity injuries in this age group) 2

   • Distinguished by: point tenderness, swelling, older age (mean 39 months vs 27 months)
   • Most common: supracondylar, distal radius/ulna buckle fractures

2. Soft tissue injury (13% of cases) 2

   • Sprains, contusions
   • May have localized tenderness and swelling

3. Infection (rare but critical)

   • Osteomyelitis, septic arthritis
   • Consider especially in children <6 months old 2
   • Presents with fever, systemic symptoms, refusal to move limb

4. Neurologic impairment (very rare)

   • Brachial plexus injury
   • Consider with birth trauma history or unusual mechanism

Management Algorithm

Immediate reduction is both diagnostic and therapeutic:

1. Attempt reduction without radiographs if clinical presentation is classic
2. Pronation technique is preferred over supination (less failure rate: RR 0.45,95% CI 0.28-0.73; also less painful) 7
3. Successful reduction indicated by:
   • Palpable "click" during maneuver
   • Child resumes normal arm use within minutes to hours
   • Resolution of pain
4. If reduction fails: Obtain radiographs to exclude fracture
5. Follow-up: All children without fractures should recover within 1 week 2

Critical Pitfalls to Avoid

• Don't assume all arm injuries in toddlers are pulled elbow: Multivariate analysis shows swelling and point tenderness strongly correlate with fractures 2
• Don't miss non-traumatic causes in infants <6 months: Infection and neurologic causes are more likely in this age group 2
• Don't forget atypical mechanisms: Pulled elbow can occur without classic traction (e.g., rolling over on trapped arm) 3
• Don't delay imaging if uncertain: When clinical picture is atypical, radiographs are essential to exclude fracture
• Don't ignore persistent symptoms: If child doesn't improve within 1 week, reassess for alternative diagnosis 2

The diagnosis of nursemaid's elbow relies heavily on pattern recognition: young age, characteristic mechanism, absence of swelling, and pronated immobile arm position create a clinical picture that allows confident diagnosis and immediate treatment without imaging in most cases.