Mechanism of Injury in Nursemaid's Elbow
Nursemaid's elbow (radial head subluxation) occurs when a longitudinal traction force pulls the radial head through the annular ligament, most commonly from lifting or pulling a child by the arm.
Classic Traction Mechanisms
The primary mechanism involves axial traction on an extended and pronated forearm 1, 2. The most common specific scenarios include:
- Lifting the child by the arms (28.3% of cases)
- "Wrestling" with the child (12.3%)
- Swinging the child by the arms (9.2%)
- Placing child into/out of a seat (4.3%)
- Child pulling away from parent
- Tripping while hand is held
These traction mechanisms account for approximately 63% of all nursemaid's elbow cases 1.
Caregiver-Specific Patterns
The mechanism varies significantly by caregiver gender 1:
Male caregivers are more likely involved in:
- Swinging by arms (OR 3.2)
- Lifting (OR 1.9)
- Wrestling (OR 6.4)
Female caregivers are more commonly associated with:
- Child pulling away (OR 2.3)
- Tripping (OR 2.0)
- Getting dressed (OR 2.1)
Non-Axial Traction Mechanisms
Importantly, nursemaid's elbow can occur without the classic pulling mechanism 3. Non-axial mechanisms include:
- Falls (57% of non-traction cases)
- Direct blow to the elbow (16%)
- Rolling over in bed (7%)
This is a critical pitfall—clinicians should not exclude nursemaid's elbow simply because the classic traction history is absent 3.
Anatomic Basis
The injury occurs because the radial head diameter is smaller relative to the neck in young children, allowing the radial head to slip through the annular ligament when traction is applied to the extended, pronated forearm 2. This anatomic vulnerability explains why the injury predominantly affects children aged 1-4 years.
Recurrence and Hyperlaxity
Joint hyperlaxity significantly increases recurrence risk 4. Children with higher Beighton scores for joint laxity experience more frequent dislocations, though the radial head-neck ratio does not predict recurrence 4.
Critical Age Consideration
In nonambulatory infants, suspected nursemaid's elbow should prompt radiographic evaluation before reduction attempts 5. The diagnosis is uncommon in this age group, and fractures (including those suggesting abuse) may be misdiagnosed as radial head subluxation 5.