In an adult without comorbidities who has a minimally displaced Zone 1 avulsion or nondisplaced Zone 2 Jones fracture of the base of the fifth metatarsal, how many weeks should a controlled‑motion (CAM) boot be used?

Duration of CAM Boot Treatment for Base of Fifth Metatarsal Fractures

For minimally displaced Zone 1 avulsion fractures or nondisplaced Zone 2 Jones fractures of the fifth metatarsal base, a CAM boot should be worn for 4–6 weeks, followed by transition to functional support (ankle brace or hard-soled shoe) for an additional 2–4 weeks. 1, 2, 3

Initial Immobilization Period (4–6 Weeks)

• Zone 1 (tuberosity avulsion) fractures heal faster than Zone 2 fractures, with radiographic union typically occurring at 7.2 weeks in a CAM boot versus 8.6 weeks in a hard-soled shoe 3
• Zone 2 (Jones) fractures require the full 4–6 weeks of non-weight-bearing cast or CAM boot immobilization due to their retrograde vascular supply and higher risk of nonunion 4, 5
• Protected weight-bearing in a cast shoe or CAM boot for 4–6 weeks is the standard conservative approach for nondisplaced metatarsal fractures 5

Transition to Functional Support (Additional 2–4 Weeks)

• After the initial 4–6 week immobilization period, transition to functional support (ankle brace or hard-soled shoe) for 2–4 additional weeks provides optimal outcomes while preventing complications of prolonged rigid immobilization 2
• Total treatment duration is typically 6–10 weeks from injury to full return to activities 1, 3
• Patients treated with CAM boots return to prior activity levels at an average of 8.3 weeks, compared to 9.7 weeks with hard-soled shoes alone (though this difference was not statistically significant) 3

Weight-Bearing Protocol

• Zone 1 fractures: Immediate weight-bearing as tolerated is safe and does not compromise healing 1, 6
• Zone 2 fractures: Non-weight-bearing for the first 2 weeks, then progressive protected weight-bearing (25% at week 3,50% at week 4,75% at week 5,100% at week 6) 4
• Early fracture stabilization through proper immobilization provides superior pain relief compared to medications alone 1

Rehabilitation Considerations

• Avoid prolonged immobilization beyond 6–8 weeks, as this leads to stiffness, muscle atrophy, and poor functional outcomes without improving healing 1, 7
• Early introduction of physical training and muscle strengthening should begin after the initial immobilization period, followed by balance training 1, 7
• Ankle range-of-motion exercises should start at 2–6 weeks postinjury 4

Radiographic Monitoring

• Follow-up radiographs at 4,8, and 12 weeks are necessary to confirm proper healing and alignment 1, 3
• Zone 1 fractures demonstrate complete radiographic healing at an average of 7.2 weeks with CAM boot treatment 3
• If a fracture line remains lucent at 4 weeks, MRI without contrast is the preferred advanced imaging modality to assess for occult injury or stress fracture progression 7

Critical Pitfalls to Avoid

• Do not extend rigid immobilization beyond 6 weeks without transitioning to functional support, as excessive immobilization causes stiffness and muscle weakness 1, 2
• Do not confuse Zone 1 and Zone 2 fractures, as Zone 2 (Jones) fractures have significantly higher nonunion rates (15–30% with conservative treatment) and may warrant earlier surgical consultation 4, 8
• Do not allow immediate full weight-bearing for Zone 2 fractures, as these require initial non-weight-bearing due to their watershed blood supply 4, 5
• Fracture displacement >2 mm, intra-articular involvement, or multiple fragments do not necessarily require surgery for Zone 1 fractures, as functional treatment yields excellent results regardless of these characteristics 6

When to Consider Surgical Referral

• Arrange orthopedic consultation within 24–48 hours for displaced fractures (>2 mm) or confirmed Zone 2 Jones fractures, particularly in high-level athletes 1, 4
• Surgical fixation achieves union rates of 89–100% and radiographic healing between 6–10 weeks, compared to 15–30% nonunion rates with conservative treatment of Zone 2 fractures 4, 8
• Comminuted fractures or those with proximal-split patterns are not suitable for percutaneous screw fixation and require alternative surgical approaches 4