Best Immobilization Method for Fifth Metatarsal Fractures
For fifth metatarsal fractures, a controlled ankle motion (CAM) walker boot is the most effective immobilization method, providing superior pressure offloading compared to postoperative sandals or standard shoes while allowing for earlier bone healing. 1
Classification of Fifth Metatarsal Fractures
Understanding the type of fracture is crucial for determining appropriate immobilization:
Zone 1 (Tuberosity/Avulsion) Fractures:
- Most common type at the base of the fifth metatarsal
- Usually caused by inversion injuries
Zone 2 (Jones Fractures):
- Acute fractures at the metaphyseal-diaphyseal junction
- Higher risk of delayed union or nonunion
Zone 3 (Diaphyseal Stress Fractures):
- Proximal diaphyseal stress fractures
- Highest risk of nonunion
Immobilization Options and Evidence
CAM Walker Boot
- Primary recommendation for most fifth metatarsal fractures
- Significantly reduces peak pressure and contact pressure at the fifth metatarsal during walking and heel-walking compared to postoperative sandals 1
- Provides better immobilization of the foot and ankle
- Results in faster bone healing (average 7.2 weeks) compared to hard-soled shoes (8.6 weeks) 2
Hard-Soled Shoe
- Acceptable alternative for stable, minimally displaced Zone 1 fractures
- Less effective at offloading the fifth metatarsal compared to CAM walker boots 1
- May be appropriate for less active patients with stable fractures
- Average time to bone healing is 8.6 weeks 2
Non-Weight Bearing Cast Immobilization
- Recommended for true Jones fractures (Zone 2)
- Non-weight bearing for 6-8 weeks with success rates of 72-93% 3
- Provides maximum immobilization but limits function
Treatment Algorithm Based on Fracture Type
Zone 1 (Tuberosity/Avulsion) Fractures:
- If displacement <2mm and <30% joint involvement:
Zone 2 (Jones Fractures):
- Non-displaced or minimally displaced:
- Non-weight bearing CAM walker boot or cast for 6-8 weeks 3
- Displaced >2mm:
- Consider surgical fixation, especially in active patients 3
Zone 3 (Diaphyseal Stress Fractures):
- Often require surgical intervention due to high nonunion rates
- If conservative treatment is chosen, use non-weight bearing CAM walker boot for 6-8 weeks 3
Follow-up Considerations
Recent evidence suggests that routine follow-up may not be necessary for uncomplicated fifth metatarsal fractures 5. A structured protocol with:
- Initial immobilization with CAM walker boot or hard-soled shoe
- Weight bearing as tolerated
- Patient education with access to care if needed
- Selective follow-up for high-risk fractures only
This approach has shown no increase in complications while significantly reducing unnecessary outpatient visits 5.
Important Considerations
- Splinting is useful to reduce pain, prevent further injury, and facilitate transport in the first aid setting 6
- For initial assessment, standard radiographs (anteroposterior, lateral, and mortise views) should include the base of the fifth metatarsal 6
- Monitor for signs of poor perfusion (blue, purple, or pale extremities) which require immediate medical attention 6
- Cover open fractures with clean dressing to prevent contamination 6
- Compliance with immobilization is crucial for optimal outcomes 7
Common Pitfalls to Avoid
- Misdiagnosis of Jones fractures as ankle sprains due to similar mechanism of injury
- Inadequate immobilization leading to delayed union or nonunion
- Prolonged immobilization causing joint stiffness and muscle atrophy
- Premature weight bearing on unstable fractures
- Failure to recognize displacement that might require surgical intervention
By selecting the appropriate immobilization method based on fracture type and displacement, most fifth metatarsal fractures can be successfully treated with excellent outcomes and minimal complications.