Management of Lateral Avulsion Fracture of the Fourth Metatarsal Base
A minimally displaced lateral avulsion fracture of the fourth metatarsal base with a 3-mm fragment should be treated with protected weight-bearing in a removable boot or cast shoe for 4–6 weeks, as this approach allows faster return to activity than rigid casting while achieving reliable healing. 1, 2
Understanding the Injury Pattern
This injury represents a ligamentous avulsion fracture at the lateral base of the fourth metatarsal, typically caused by forefoot adduction forces similar to the more commonly recognized fifth metatarsal base avulsions. 3 The 3-mm fragment size and lateral location strongly suggest an avulsion mechanism involving the lateral ligamentous attachments rather than a direct impact injury. 3
Conservative Management Protocol
Immobilization Strategy
Use a soft dressing (Jones dressing) or pneumatic walking boot rather than a rigid short leg cast. 1 A prospective randomized study demonstrated that soft dressing treatment resulted in return to full activity in an average of 33 days compared to 46 days with rigid casting, with superior functional scores (92 vs 86) and no compromise in union rates. 1
Allow protected weight-bearing as tolerated from the outset. 2 Complete non-weight-bearing is not necessary for minimally displaced avulsion fractures. 1, 2
Continue immobilization for 4–6 weeks total. 2 Fourth metatarsal base injuries may require longer healing times than typical lesser metatarsal fractures, sometimes extending to 8 weeks or more. 3
Expected Healing Timeline
- Radiographic evidence of healing typically appears by 44–65 days on average. 1
- Return to full physical activity usually occurs within 96 days. 1
- Be aware that proximal fourth metatarsal injuries can take 2–8 months for complete resolution in athletes, longer than more distal metatarsal fractures. 3
When to Consider Surgical Management
Surgery is NOT indicated for this fracture based on the following criteria:
Surgical intervention for metatarsal avulsion fractures is reserved for displacement >2 mm with >30% joint involvement. 2, 4 Your 3-mm fragment refers to fragment size, not displacement.
The lateral location at the fourth metatarsal base typically involves minimal articular surface. 3
If the fracture were truly displaced >2 mm with significant joint involvement, open reduction with tension-band wiring or screw fixation would be indicated. 2
Critical Monitoring Points
Watch for Delayed Union
Some patients remain symptomatic even after 3 months of immobilization, similar to proximal fifth metatarsal injuries. 3 This does not automatically indicate treatment failure.
If pain persists beyond 8–12 weeks despite appropriate immobilization, obtain repeat radiographs to assess for nonunion. 3, 4
Asymptomatic Nonunion
Conservative management of fifth metatarsal avulsion fractures (the closest analog with robust data) results in asymptomatic nonunion in approximately 35% of cases, yet all patients become asymptomatic by 1 year. 4 Similar patterns may occur with fourth metatarsal base avulsions. 3
Asymptomatic nonunion does not require surgical intervention. 4
Common Pitfalls to Avoid
Do not confuse fragment size (3 mm) with displacement. 2, 4 A 3-mm fragment that is minimally displaced does not meet surgical criteria.
Do not use rigid casting as first-line treatment. 1 This delays return to function without improving outcomes.
Do not expect rapid healing comparable to distal metatarsal fractures. 3 Proximal fourth metatarsal injuries behave more like proximal fifth metatarsal injuries with prolonged healing times.
Ensure imaging includes the entire metatarsal base to rule out associated injuries. 5 Standard foot radiographs should extend to visualize the fifth metatarsal base and adjacent structures.