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

Treatment of Fifth Metatarsal Base Avulsion Fractures

Most fifth metatarsal base avulsion fractures should be treated conservatively with early functional mobilization using a removable walking boot or brace, allowing immediate weight-bearing as tolerated, with surgical fixation reserved only for fractures displaced >2mm or involving >30% of the cubometatarsal joint. 1, 2, 3

Initial Assessment and Imaging

• Obtain standard three-view radiographs (anteroposterior, lateral, and mortise) that include the base of the fifth metatarsal to confirm the diagnosis 4, 1
• Weight-bearing radiographs provide critical information about fracture stability and should be obtained when possible 1
• Measure the degree of displacement carefully on radiographs, as this determines treatment approach 2, 3
• Avoid manipulating the ankle before obtaining radiographs unless there is neurovascular compromise or critical skin injury 1

Treatment Algorithm Based on Displacement

Non-displaced or Minimally Displaced Fractures (<2mm)

Conservative functional treatment is the standard of care for these fractures. 5, 3

• Apply initial short leg cast or compression dressing for 2-3 days with anti-inflammatory medication until edema subsides 5
• Transition to a removable walking boot (pneumatic boot or orthopedic brace like Caligamed II) after swelling reduces 5, 6
• Allow immediate weight-bearing as tolerated—patients typically achieve full weight-bearing within 9 days 6
• Continue boot immobilization for 5-6 weeks with repeat radiographs to confirm healing 5
• Average return to full activity occurs at 33 days with soft dressing/boot versus 46 days with rigid casting 7

A soft Jones dressing or removable boot is superior to rigid short leg casting because it allows faster return to activity (33 vs 46 days) and produces better functional outcomes (modified foot score 92 vs 86) without compromising union rates 7

Displaced Fractures (>2mm displacement or >30% joint involvement)

Surgical fixation is indicated to eliminate nonunion risk and ensure timely return to activity. 2, 3

• Options include open reduction with internal fixation or closed reduction with percutaneous fixation 2
• Surgical management eliminates the 35.5% asymptomatic nonunion rate seen with conservative treatment of displaced fractures 2
• All surgically treated patients in comparative studies achieved union without complications 2

Rehabilitation Protocol

• Begin progressive weight-bearing immediately after initial immobilization period 1
• Introduce early physical training and muscle strengthening once boot is removed at 5-6 weeks 4
• Implement long-term balance training and fall prevention exercises 4
• Avoid prolonged rigid immobilization beyond 6 weeks to prevent stiffness and muscle atrophy 4

Expected Healing Timeline

• Radiographic evidence of healing appears by average 44 days (range up to 65 days) for conservatively managed fractures 7
• All patients return to full weight-bearing and activity within 96 days 7
• Average sick leave duration is 19 days with functional boot treatment 6
• Final clinical follow-up should occur at 12 weeks 5

Special Populations Requiring Extra Attention

Patients with Diabetes and Neuropathy

• Ensure proper fitting of orthotic devices to prevent pressure sores 1
• Implement careful offloading strategies to prevent ulceration at the fracture site 1
• Monitor closely for signs of skin breakdown or infection 1
• Consider non-removable offloading devices if compliance is questionable 8

Common Pitfalls to Avoid

• Do not use rigid short leg casts for routine avulsion fractures—they prolong recovery without improving outcomes 7
• Do not obtain unnecessary foot or knee radiographs in isolated fifth metatarsal fractures as they have low diagnostic yield 1
• Do not accept >2mm displacement with conservative treatment—this leads to 35.5% nonunion rate even if asymptomatic 2
• Do not immobilize longer than necessary—prolonged immobilization causes preventable stiffness and muscle atrophy 4

Key Decision Point

The critical threshold is 2mm of displacement: fractures below this can be treated functionally with excellent outcomes, while those above require surgical fixation to prevent nonunion and optimize recovery 2, 3