How to treat an avulsion fracture on the 5th metatarsal bone at the proximal end near the cubometatarsal joint?

Treatment of Avulsion Fracture on the 5th Metatarsal at the Proximal End

For avulsion fractures of the base of the fifth metatarsal, conservative treatment with a soft dressing or orthopedic boot allowing early weightbearing is recommended over casting, as it provides faster return to activity without compromising healing outcomes. 1

Diagnosis and Assessment

• Initial evaluation should include three standard radiographic views: anteroposterior, lateral, and mortise views that include the base of the fifth metatarsal bone 2
• Radiographs are indicated in patients who meet Ottawa Ankle Rules criteria, which have 92-99% sensitivity for detecting fractures 2
• Weight-bearing radiographs, when possible, provide important information about fracture stability 2

Classification of Fifth Metatarsal Fractures

• Avulsion fractures occur at the most proximal portion (tuberosity/styloid process) where the lateral band of plantar fascia attaches (Zone A) 3
• Jones fractures occur at the metaphyseal-diaphyseal junction (Zone B), where the peroneus brevis tendon attaches 3
• Shaft fractures occur distal to the tuberosity 4

Treatment Algorithm for Avulsion Fractures

Conservative Management (Recommended for most cases)

• Indicated for non-displaced or minimally displaced (<2mm) avulsion fractures 4, 5
• Options include:
  • Soft (Jones) dressing - allows faster return to activity (average 33 days) compared to casting (46 days) 1
  • Orthopedic boot with early weightbearing - allows full weightbearing after approximately 9 days with average sick leave of 19 days 6
  • Below-knee cast - effective but results in longer recovery time 1

Surgical Management

• Indicated when:
  • Displacement is >2mm 4, 5
  • More than 30% of the cubometatarsal joint surface is involved 4
• Surgical options include:
  • Open reduction with internal fixation
  • Closed reduction with percutaneous fixation 5

Expected Outcomes

• Radiographic evidence of fracture healing is typically present by 65 days, with an average of 44 days 1
• Return to full weightbearing and physical activity occurs within 96 days 1
• Surgical management eliminates the risk of nonunion compared to conservative treatment (0% vs 35.5% nonunion rate) 5
• Despite higher nonunion rates with conservative management, patients are typically asymptomatic at 1-year follow-up regardless of treatment method 5

Clinical Pearls and Pitfalls

• Avulsion fractures at the base of the fifth metatarsal are often confused with Jones fractures, which have different treatment protocols and higher nonunion rates 4
• The anatomical location of the fracture determines the likely mechanism and guides treatment - Zone A fractures (plantar fascia avulsion) can often be treated conservatively with weightbearing, while Zone B/C fractures may require more aggressive management 3
• Avoid unnecessary immobilization, as early functional treatment with appropriate supportive footwear leads to better outcomes and faster return to activities 1, 6
• Even with conservative management, patients should be counseled about the possibility of asymptomatic nonunion (approximately 35%) 5