What type of cast is recommended for an isolated radial shaft fracture?

Cast Selection for Isolated Radial Shaft Fractures

For isolated radial shaft fractures, rigid immobilization with a long arm cast (above-elbow) is recommended as the primary treatment option for non-displaced or minimally displaced fractures.

Initial Assessment and Treatment Decision

When evaluating a patient with an isolated radial shaft fracture, the treatment approach depends on:

• Fracture displacement
• Fracture angulation
• Fracture stability
• Patient factors

Treatment Algorithm:

1. Non-displaced or minimally displaced fractures:

   • Rigid immobilization with cast
   • Monitor for displacement with serial radiographs

2. Displaced fractures (>3mm shortening, >10° angulation):

   • Surgical fixation is typically required 1
   • Open reduction and internal fixation (ORIF) with plating is the gold standard 2

Cast Type Recommendations

For Non-Displaced/Minimally Displaced Fractures:

• Primary recommendation: Long arm cast (above-elbow)
  • Immobilizes the elbow to prevent forearm rotation
  • Better controls rotational forces that could displace the fracture

While the AAOS guidelines do not provide definitive recommendations specifically for radial shaft fractures (focusing more on distal radius fractures), they do suggest rigid immobilization for displaced distal radius fractures with moderate strength recommendation 1.

Important Considerations:

• Duration of immobilization: Minimum of 6-10 weeks until radiographic union is evident 3
• Follow-up: Serial radiographs at 1,2, and 3 weeks to ensure maintenance of reduction 1
• Conversion to short arm cast: May be considered after initial 3-4 weeks if fracture shows early stability

Evidence Analysis

The evidence regarding elbow immobilization in radial shaft fractures is limited. For distal radius fractures, one randomized controlled trial compared above-elbow to below-elbow splinting for maintenance of reduction and found no significant differences 1. However, radial shaft fractures differ biomechanically from distal radius fractures.

A 2019 study by Caruso et al. found no significant difference between above- and below-elbow casts for distal radius fractures 4, but this cannot be directly extrapolated to radial shaft fractures, which are subject to different biomechanical forces.

Pitfalls and Caveats

1. Risk of displacement: Inadequate immobilization may lead to malunion or nonunion

2. Compartment syndrome: Monitor for signs in the first 24-48 hours

3. Stiffness: Prolonged immobilization may lead to elbow and wrist stiffness

4. Associated injuries: Always assess for:

   • Ulnar fractures (both-bone fractures)
   • Monteggia fracture-dislocations
   • Galeazzi fracture-dislocations
   • Essex-Lopresti injuries
   • Neurovascular compromise (particularly posterior interosseous nerve)

5. Occult fractures: If initial radiographs are negative but clinical suspicion remains high, CT imaging may be necessary to identify occult fractures 1

Special Situations

• Isolated midshaft ulna fractures (nightstick fractures) can often be treated with immobilization if minimally displaced 3
• Combined radius and ulna fractures generally require surgical fixation 3
• Proximal radial shaft fractures have higher rates of nonunion and may benefit from surgical intervention even with minimal displacement 5

Remember that while cast immobilization is appropriate for stable fractures, surgical fixation remains the gold standard for displaced radial shaft fractures to ensure proper alignment and functional outcomes.