What is the treatment and management plan for a distal fibula fracture treated with a Controlled Ankle Movement (CAM) boot?

Treatment and Management of Distal Fibula Fracture with CAM Boot

For isolated, minimally displaced distal fibular fractures, a CAM boot is the preferred conservative treatment option, providing superior outcomes with fewer complications compared to rigid casting. 1

Initial Assessment and Stability Determination

Before proceeding with CAM boot treatment, you must confirm fracture stability by evaluating:

• Medial clear space <4mm on weight-bearing radiographs indicates a stable ankle fracture suitable for conservative management 1
• Absence of medial tenderness, bruising, or swelling (which would suggest deltoid ligament injury and potential instability requiring surgical consideration) 1
• Fracture location at or below the syndesmosis level—fractures above the syndesmosis carry higher risk of syndesmotic injury 1
• No bi- or trimalleolar involvement, as these are inherently unstable and typically require surgical fixation 1

CAM Boot Application Protocol

• Apply the CAM boot with the ankle maintained at 90 degrees (neutral position) to prevent equinus contracture 1
• The boot should extend from below the knee to the toes, similar to a posterior splint positioning 1
• This positioning accommodates anticipated swelling in the first 48-72 hours 1

Immediate Mobilization Strategy

• Initiate active toe motion exercises immediately following diagnosis to prevent stiffness, which is one of the most functionally disabling complications 1
• Toe motion does not adversely affect adequately stabilized fractures 1
• In pediatric populations, CAM boot treatment demonstrates improved range of motion, higher patient satisfaction (5.26 vs 4.25 for casting), and significantly lower complications (0.04/patient vs 0.54/patient for casting) at 4 weeks 2

Duration and Follow-up Timeline

• Maintain CAM boot immobilization for approximately 3 weeks 1
• Obtain radiographic follow-up at 3 weeks to confirm adequate healing 1
• Perform weight-bearing radiographs at follow-up to reassess the medial clear space and confirm continued stability 1
• At 8 weeks, patients treated with CAM boots show 0% continued symptoms compared to 15.4% with casting 2

Common Pitfalls to Avoid

• Do not miss associated injuries: Always examine for medial ankle tenderness, syndesmotic injury, or Maisonneuve fracture patterns 1
• Monitor for complications including skin irritation and muscle atrophy, which occur in approximately 14.7% of immobilization cases 1
• If post-reduction imaging shows radial shortening >3mm, dorsal tilt >10°, or intra-articular displacement in any associated injuries, surgical fixation is indicated 1

When Conservative Treatment Fails

For unstable fractures (medial clear space ≥4mm) or those with proven instability, surgical management is required rather than CAM boot treatment 3. However, for stable isolated type B fibula fractures with medial clear space ≤6mm, non-operative treatment with CAM boot provides equivalent long-term functional outcomes (OMAS score 84, AOFAS 93) while avoiding the 33% revision surgery rate for hardware removal seen with operative treatment 3.