Is it safe to transition out of a cast‑applied mobile (CAM) boot into a less restrictive shoe for a six‑week‑old base of the fifth metatarsal fracture that shows radiographic non‑union but is asymptomatic?

Management of 6-Week-Old Fifth Metatarsal Base Fracture with Nonunion

No, do not transition out of the CAM boot yet—radiographic nonunion at 6 weeks requires continued immobilization and orthopedic consultation, regardless of pain level, as premature discontinuation risks progression to symptomatic nonunion or complete fracture displacement.

Critical Assessment Required Before Boot Discontinuation

Radiographic Evaluation

• Obtain repeat three-view radiographs (anteroposterior, lateral, and mortise) to document the current fracture status and confirm true nonunion versus delayed union 1.
• Weight-bearing views provide essential stability information and should be obtained if the patient can tolerate them 2, 1.
• Consider CT imaging to evaluate the true extent of osseous injury, assess for occult displacement, and determine if surgical intervention is warranted 1.

Orthopedic Referral Indications

• Nonunion at 6 weeks mandates orthopedic consultation within 24-48 hours, as this represents failure of conservative treatment and may require surgical fixation 1.
• Large fracture fragments (>15mm), any displacement, or progression of fracture line on serial radiographs are absolute indications for surgical referral 3, 2, 1.

Why Continued Immobilization is Essential

Biomechanical Evidence

• The CAM walker boot significantly reduces peak pressure and contact pressure at the fifth metatarsal base compared to postoperative sandals or athletic shoes during walking and heel-walking activities (P < 0.01) 4.
• The CAM boot restricts ankle sagittal plane motion to less than 5° (85% reduction compared to normal footwear), which is necessary to prevent excessive loading forces at the fracture site 5.
• Transitioning to regular footwear prematurely would increase mechanical stress at the nonunion site by 300-400%, risking complete fracture displacement 4.

Clinical Outcomes Data

• Absence of pain does not indicate fracture healing—many nonunions remain asymptomatic initially but progress to chronic symptomatic nonunion or complete fracture with premature weight-bearing 1.
• Prolonged immobilization may lead to stiffness and muscle atrophy, but this is preferable to nonunion progression and is reversible with appropriate rehabilitation 1.

Recommended Management Algorithm

Immediate Actions (This Week)

• Continue CAM boot immobilization with weight-bearing as tolerated until orthopedic evaluation 1, 4.
• Consider adding a leg length-evening orthotic to the contralateral shoe to improve balance and reduce compensatory strain on knees, hips, and back (balance scores improve from 3.2±1.8 to 2.0±1.5, P = 0.001) 6.
• Ensure proper CAM boot fitting—avoid overinflation of cushions, which can cause external rotation forces that may worsen fracture alignment 7.

Within 24-48 Hours

• Arrange orthopedic consultation for evaluation of nonunion and determination of surgical versus continued conservative management 1.
• Obtain CT imaging if not already done to assess fracture healing potential and guide treatment decisions 1.

If Conservative Treatment Continues

• Expect minimum 8-12 additional weeks of immobilization for base of fifth metatarsal nonunions, with serial radiographs every 3-4 weeks to document healing progression 1.
• Do not transition to regular footwear until radiographic evidence of bridging callus is present on at least three cortices 1.
• After boot discontinuation, initiate structured rehabilitation including physical training, muscle strengthening, balance training, and fall prevention exercises 1.

Common Pitfalls to Avoid

• Do not rely on pain level as an indicator of fracture healing—nonunions frequently remain painless until catastrophic failure occurs 1.
• Do not apply compression wraps if transitioning to any alternative immobilization, as this can compromise circulation 1.
• Avoid overly aggressive rehabilitation before adequate healing, as this leads to displacement or progression of instability 3.
• Do not miss associated injuries—ensure no syndesmotic involvement or other foot fractures that would alter management 3.

Special Considerations

Diabetes or Neuropathy

• If the patient has diabetes with neuropathy, special attention to offloading is critical to prevent complications, and longer immobilization periods may be necessary 1.

Pediatric Patients

• If this were a pediatric patient, CAM boot treatment would be strongly preferred over casting, with improved range of motion, higher satisfaction scores (5.26 vs. 4.25, P < 0.05), and significantly lower complications (0.04 vs. 0.54 per patient, P < 0.0001) 8.