How should I evaluate and manage an 18‑month‑old with left arm pain after a ~3‑foot fall, who has full range of motion and no obvious deformity?

Obtain X-rays of the Left Arm Immediately

For an 18-month-old with arm pain after a 3-foot fall who cries with specific movements (lifting arm, clapping) despite full range of motion and no obvious deformity, you should obtain radiographs of the affected extremity to rule out occult fracture before considering other diagnoses like radial head subluxation.

Clinical Reasoning

Age-Specific Fracture Risk

At 18 months, this child falls into a critical age group where fractures are common but can be subtle. In children 12-23 months old with any fracture from trauma, skeletal survey becomes necessary depending on fracture type and mechanism 1. While a 3-foot fall from a bed is a plausible mechanism for injury, the persistent pain with specific movements warrants imaging.

Key Clinical Findings That Guide Imaging

The child demonstrates:

• Pain with specific movements (lifting arm, clapping) - this functional limitation is significant
• Full range of motion - suggests no complete dislocation but doesn't exclude fracture
• No obvious deformity or swelling - can still have occult fractures, particularly torus/buckle fractures

Research shows that point tenderness and swelling correlate with fractures, while decreased arm movement without swelling correlates with radial head subluxation (RHS) 2. However, your patient has pain with movement but maintains full ROM - an intermediate presentation requiring imaging first.

Recommended Imaging Approach

Initial Imaging: Radiographs

Start with AP and lateral radiographs of the entire left arm (humerus, elbow, forearm) 3, 4. In young children who cannot localize symptoms precisely, broader imaging is appropriate initially 3.

Specific views needed:

• Humerus (AP and lateral)
• Elbow (AP and lateral)
• Forearm/wrist if pain extends distally

Why Radiographs First?

1. Toddler fractures and subtle injuries are common - Torus (buckle) fractures, spiral tibial fractures in lower extremity, and similar patterns occur in upper extremity 5, 2

2. Falls from 3 feet can cause fractures - While short falls rarely cause severe injury, they definitely cause fractures, especially in the distal metaphysis 5, 6

3. Age 18 months is peak fracture risk - Mean age for fractures is 39 months vs. 27 months for RHS 2

If Radiographs Are Normal

Consider Radial Head Subluxation (Nursemaid's Elbow)

If X-rays show no fracture and the mechanism could involve a pulling force (even if not clearly reported):

Attempt reduction using hyperpronation technique:

• More successful than flexion/supination method 7
• Safe to attempt after fracture is excluded
• Immediate improvement in arm use confirms diagnosis

Point-of-Care Ultrasound (POCUS) Option

If available and you have expertise, POCUS can screen for fracture before X-ray 8. A normal ultrasound screen increases safety of attempting RHS reduction. However, this requires specific training and shouldn't delay definitive imaging if unavailable.

Critical Red Flags to Assess

Child Abuse Screening

At 18 months with a fracture from reported minor trauma, you must evaluate for abuse 1:

• 20-25% of fractures in children <12 months are from abuse
• 6-7% in children 12-23 months are from abuse
• History inconsistent with injury severity
• Delay in seeking care
• Multiple injuries or fractures at different healing stages
• Concerning social history

If fracture is found and mechanism seems inadequate or history is concerning, skeletal survey is necessary 1.

Vascular Compromise

Examine for:

• Normal capillary refill
• Warm extremity
• Normal color (not blue, purple, or pale)
• Palpable pulses if possible

Follow-Up Plan

If Fracture Found:

• Appropriate immobilization based on fracture type
• Orthopedic referral as needed
• Pain management
• Evaluate for abuse if mechanism inadequate

If No Fracture and No Improvement After RHS Reduction:

• Immobilize in sling for comfort
• Follow-up in 3-5 days
• Return precautions: worsening pain, inability to use arm, fever, swelling
• Consider repeat X-rays in 7-10 days if symptoms persist (some fractures only visible on follow-up) 3

If Symptoms Persist Beyond 1 Week:

Consider MRI without contrast for:

• Occult fracture
• Soft tissue injury
• Osteomyelitis (especially if any fever or systemic symptoms develop)

Common Pitfalls to Avoid

1. Don't assume full ROM excludes fracture - Torus fractures can have preserved motion
2. Don't attempt RHS reduction before imaging in this age group - Fracture risk is too high
3. Don't dismiss parental concern - Persistent pain with specific activities is significant
4. Don't forget abuse screening - This age and mechanism require heightened awareness 9, 1

The priority is morbidity prevention through early fracture detection and ensuring this isn't a sentinel injury from abuse that could lead to more severe harm if missed.