Should a short arm cast or a long arm cast be used for a Salter-Harris II fracture of the distal radius in a 9-year-old?

Short Arm Cast for Salter-Harris II Distal Radius Fractures in 9-Year-Olds

A well-molded short arm cast is as effective as a long arm cast for treating Salter-Harris II fractures of the distal radius in a 9-year-old child, provided the fracture is not completely displaced and the cast is properly molded. 1, 2

Treatment Algorithm

Initial Assessment and Reduction

• Perform closed reduction if the fracture is displaced 3
• Assess for complete displacement, as completely displaced fractures may have soft tissue interposition (flexor tendons, periosteum, pronator quadratus) that prevents adequate closed reduction 4
• If closed reduction fails or the fracture is completely displaced, consider open reduction as repeated forceful manipulations risk growth arrest, compartment syndrome, and avascular necrosis 4

Cast Selection Based on Displacement Pattern

For partially displaced or minimally displaced Salter-Harris II fractures:

• Use a short arm cast as the primary immobilization method 1, 2
• This provides equivalent fracture stability compared to long arm casting 1, 2
• Short arm casts result in faster return to normal elbow range of motion (median 4.5 days faster) and less interference with daily activities 2

For completely displaced fractures:

• Consider long arm cast or surgical fixation, as these fractures have higher risk of soft tissue interposition and loss of reduction 4, 2
• Completely displaced fractures were excluded from studies showing equivalence of short and long arm casts 2

Critical Technical Requirements

Cast Molding Quality

• Ensure excellent three-point molding with a cast index <0.8 at the fracture site 1
• Poor cast molding (higher cast index) is the primary predictor of loss of reduction, regardless of whether short or long arm casting is used 1
• The cast must never obstruct full finger range of motion 5

Immediate Post-Reduction Management

• Initiate active finger motion exercises immediately to prevent stiffness 5
• Finger motion does not adversely affect adequately stabilized fractures 5

Follow-Up Protocol

• Obtain radiographs at approximately 1 week post-reduction to detect early loss of reduction 6, 1
• Continue radiographic monitoring at 3 weeks and at cast removal 5
• Total immobilization duration is typically 4-6 weeks for pediatric distal radius fractures 6, 1

Common Pitfalls to Avoid

• Do not use long arm casts routinely for all distal radius fractures in children ≥4 years old, as they provide no additional stability benefit when casts are well-molded but significantly impair function 1, 2
• Avoid repeated forceful manipulation attempts if closed reduction fails, as this increases risk of growth disturbance and neurovascular complications 4
• Do not restrict finger motion at any point during treatment, as this increases stiffness risk without improving fracture stability 5
• Watch for loss of reduction in the first 1-2 weeks, as this is when displacement most commonly occurs 6, 1

Indications for Surgical Intervention

Consider surgical fixation if:

• Post-reduction radial shortening >3 mm, dorsal tilt >10°, or persistent displacement occurs 7
• Closed reduction fails due to soft tissue interposition 4
• The fracture is open, unstable after multiple reduction attempts, or involves multiple trauma 3