What are the possible causes of lateral foot pain at the base of the fifth metatarsal and how should it be evaluated and managed?

Fifth Metatarsal Pain: Evaluation and Management

Initial Assessment and Imaging

Start with weight-bearing plain radiographs (anteroposterior, lateral, and oblique views) as the first-line diagnostic study for any fifth metatarsal pain. 1, 2

Clinical Evaluation Points

• Determine mechanism of injury: Forced inversion during plantar flexion suggests tuberosity avulsion fracture, while insidious onset in athletes suggests stress fracture 3, 4
• Apply Ottawa Ankle Rules: Obtain radiographs if there is point tenderness at the base of the fifth metatarsal or inability to bear weight for four steps 2
• Assess for vascular compromise immediately: Check for blue, purple, or pale foot requiring emergent intervention 2
• Examine for open wounds: Cover with clean dressing to reduce contamination risk 2

Initial Radiographic Interpretation

Radiographs have limited sensitivity (12-56%) for stress fractures early in their course, but remain the appropriate first study 1, 5. Weight-bearing views are essential for proper evaluation of metatarsal alignment and pressure distribution 5.

Differential Diagnosis by Location

Base of Fifth Metatarsal (Proximal 1.5 cm)

Two distinct fracture patterns exist with different prognoses:

• Tuberosity avulsion fractures: Result from peroneus brevis tendon pull during inversion injury 3, 6
• Jones fractures: Occur at the metaphyseal-diaphyseal junction, notorious for delayed union and nonunion 3, 6, 4

Shaft Fractures

• Typically occur in runners and heal more predictably than proximal fractures 4
• Require assessment of displacement (>3-4mm) and angulation (>10 degrees) 6

Advanced Imaging When Radiographs Are Negative

If clinical suspicion remains high despite negative radiographs, proceed directly to MRI without contrast. 1, 5

• MRI has 87-93% sensitivity for detecting occult stress fractures 5
• MRI detects stress fractures as early as bone scintigraphy but with greater specificity 5
• Critical pitfall: Radiographs miss 44-88% of stress fractures early in their course 5

Treatment Algorithm

Tuberosity Avulsion Fractures

Non-displaced fractures: Treat conservatively with weight-bearing as tolerated in supportive boot 3, 6

Surgical referral indicated for 3, 6:

• Displacement >2mm
• Comminuted fractures

• 30% involvement of cubometatarsal joint surface

• Delayed union

Jones Fractures (Use Torg Classification)

Type I (acute fracture, sharp fracture margins): Non-weight-bearing short leg cast for 6-8 weeks 3, 6

Type II (delayed union, widened fracture line): Either conservative management or surgical fixation depending on activity level 3, 6

Type III (nonunion, complete obliteration of medullary canal): Surgical management mandatory 3, 6

For athletes with Jones fractures: Consider primary surgical fixation due to high nonunion rates and prolonged healing (3+ months) even with optimal conservative care 4

Shaft Fractures

Non-displaced or minimally displaced: Conservative management 6

Surgical fixation indicated if 6:

• Displacement >3-4mm
• Angulation >10 degrees
• Options include percutaneous K-wires, plate, or screw fixation

Immediate Pain Management

Multimodal analgesia approach 2:

• Scheduled acetaminophen unless contraindicated
• Opioids cautiously if needed, particularly with unknown renal function
• Avoid NSAIDs if renal dysfunction suspected
• Early fracture stabilization through proper immobilization provides superior analgesia compared to medications alone 2

Immobilization Strategy

• Splinting reduces pain, prevents further injury, and facilitates safe ambulation 2
• Immobilize in position found unless deformity prevents safe transport 2
• Do not apply compression wraps too tightly as this compromises circulation 2
• Patients can safely bear weight immediately if pain permits when fracture pattern allows 2

Surgical Consultation Timing

Arrange surgical consultation within 24-48 hours for 2:

• Displaced fractures
• Jones fractures
• Any fracture requiring operative evaluation

Critical Pitfalls to Avoid

• Do not rely solely on initial radiographs: Proceed to MRI if clinical suspicion is high despite negative x-rays 5
• Do not underestimate healing time for Jones fractures: These require 6-8 weeks non-weight-bearing minimum and have high nonunion rates 3, 4
• Do not place ice directly on skin if using cryotherapy 2
• Do not miss diabetic foot infections: These require urgent evaluation and possible surgical intervention 1

Rehabilitation Considerations

• Early introduction of physical training and muscle strengthening followed by long-term balance training 2
• Prolonged immobilization leads to stiffness and muscle atrophy requiring appropriate rehabilitation 2
• Expect healing time of 2-8 months for stress fractures at high-risk sites 5