What is the treatment for an avulsion fracture of the fifth metatarsal foot?

Treatment of Avulsion Fractures of the Fifth Metatarsal Foot

The optimal treatment for fifth metatarsal avulsion fractures depends on displacement: conservative management with a walking boot is recommended for non-displaced or minimally displaced (<2mm) fractures, while surgical fixation is indicated for fractures displaced >2mm.

Initial Assessment and Imaging

• Radiographs are the initial imaging study of choice for suspected fifth metatarsal fractures, with standard anteroposterior, lateral, and mortise views that include the base of the fifth metatarsal 1
• Weight-bearing radiographs, when possible, provide important information about fracture stability 1
• CT and MRI are not routinely used as first-line imaging for acute trauma to the ankle/foot but may be considered for complex cases or when occult injuries are suspected 1

Treatment Algorithm

Conservative Management (for non-displaced or minimally displaced fractures <2mm)

• Walking boot (Aircast or similar) is preferred over short-leg cast 2
  • Patients treated with walking boots report:
    • Less pain between 3-12 weeks post-injury 2
    • Better function at 3,6, and 9 weeks post-injury 2
    • Earlier return to driving (6 weeks vs 12 weeks) 2
    • Less time off work (31.5 days vs 39.2 days) 2
• Duration of immobilization: 5-6 weeks 3
• Expected healing time: Average of 44 days for radiographic evidence of healing 4
• Return to full activity: Within 9 weeks with walking boot (vs 12 weeks with cast) 2

Surgical Management (for displaced fractures >2mm)

• Surgical intervention is recommended for:
  • Fractures displaced >2mm 5, 6
  • Fractures involving >30% of the cubometatarsal joint 6
• Surgical options include:
  • Open reduction with internal fixation
  • Closed reduction with percutaneous fixation 5
• Benefits of surgical management:
  • Eliminates risk of nonunion (0% nonunion rate in surgical group vs 35.5% in conservative group) 5
  • Ensures timely return to pre-injury activity levels 5

Special Considerations

• Patients with diabetes require special attention to prevent complications:
  • Proper fitting of orthotic devices to prevent pressure sores 7
  • Careful offloading to prevent ulceration at the fracture site 7
  • Thorough wound care and management 7

Rehabilitation and Follow-up

• Progressive weight-bearing as tolerated after immobilization period
• Follow-up radiographs at 5-6 weeks to assess healing 3
• Final clinical assessment at 12 weeks 3
• Patients should be counseled that even with asymptomatic nonunion (which occurs in about 35.5% of conservatively managed cases), most become asymptomatic by 1 year 5

Common Pitfalls and Caveats

• Avoid manipulation of the ankle prior to radiographs in the absence of neurovascular deficit or critical skin injury 1
• Do not perform unnecessary foot or knee radiographs in the presence of isolated fifth metatarsal fractures, as they have low yield 1
• Be aware that conservative treatment has a higher rate of asymptomatic nonunion (35.5%), though this typically doesn't affect long-term outcomes 5
• For patients with diabetes, monitor closely for signs of skin breakdown or infection at the fracture site 7