What is the treatment for a fifth metatarsal diaphysis fracture?

Treatment of Fifth Metatarsal Diaphyseal Fractures

For fifth metatarsal diaphyseal fractures, non-operative treatment with functional therapy and immediate weight-bearing is recommended as the first-line approach due to high union rates and patient satisfaction, unless the fracture is displaced more than 3-4mm or angulated more than 10 degrees, which would warrant surgical intervention. 1, 2

Diagnostic Assessment

• Obtain standard three radiographic views (anteroposterior, lateral, and mortise) for suspected fifth metatarsal fractures 3
• If radiographs are negative but clinical suspicion remains high, consider MRI 3
• Assess for:
  • Displacement (significant if >3-4mm)
  • Angulation (significant if >10 degrees)
  • Involvement of articular surface
  • Fracture location (diaphyseal vs other zones)

Treatment Algorithm

Non-operative Management (First-line for most diaphyseal fractures)

• Indicated for:

  • Non-displaced or minimally displaced fractures (<3-4mm)
  • Angulation less than 10 degrees
  • No articular involvement

• Treatment options:

  1. Functional therapy with immediate weight-bearing - Provides earlier healing and fewer adverse effects 1
  2. Hard-soled shoe - Average healing time 8.6 weeks 4
  3. CAM-walker boot - Average healing time 7.2 weeks, slightly faster than hard-soled shoe 4

• Expected outcomes:

  • Union rate of 98.5% with non-operative treatment 5
  • Average time to return to prior activities: 8-10 weeks 4
  • High patient satisfaction rate (100% in one study) 5

Surgical Management

• Indicated for:

  • Displacement >3-4mm
  • Angulation >10 degrees
  • Failure of non-operative treatment
  • Athletes or patients requiring faster return to activities

• Surgical options:

  • Percutaneous K-wire fixation
  • Plate fixation
  • Screw fixation

• Expected outcomes:

  • Mean healing time of 7.73 weeks with surgical intervention 6
  • Low complication rate (6.25%) 6
  • Low rates of nonunion (1.56%), delayed union (3.13%), and no malunions in surgical cases 6

Follow-up Protocol

• Clinical and radiographic assessment at 4,8, and 12 weeks
• Monitor for:
  • Progressive healing on radiographs
  • Pain reduction
  • Return to functional activities
  • Complications (nonunion, delayed union, malunion)

Special Considerations

• Distinguishing from other fifth metatarsal fractures: Diaphyseal fractures have different treatment protocols than proximal (Jones) fractures or avulsion fractures of the tuberosity
• Weight-bearing status: Unlike other fracture types, diaphyseal fractures can often be treated with immediate weight-bearing, which improves outcomes 1
• Surgical benefits: Even for minimally displaced fractures, surgical intervention may help maintain even weight-bearing across the metatarsal parabola 6

Common Pitfalls

1. Misclassification: Confusing diaphyseal fractures with Jones fractures (which have higher nonunion rates and different treatment protocols)
2. Over-immobilization: Extended non-weight-bearing can lead to unnecessary stiffness and delayed return to function
3. Delayed diagnosis: Stress fractures of the fifth metatarsal may initially have negative radiographs, requiring MRI for diagnosis
4. Inadequate follow-up: Failure to monitor for displacement during healing can lead to malunion

While surgical management shows good outcomes with minimal complications 6, the high union rates (98.5%) and satisfaction rates (100%) with non-operative treatment make it the preferred first-line approach for most diaphyseal fractures 5, reserving surgery for cases with significant displacement, angulation, or when rapid return to activity is critical.