What is the treatment for a Jones fracture of the fifth metatarsal in a cam (controlled ankle movement) boot?

Treatment of Jones Fracture of Fifth Metatarsal in a CAM Boot

For Jones fractures of the fifth metatarsal, a CAM boot is appropriate for non-displaced or minimally displaced fractures, but surgical fixation is recommended for displaced fractures, athletes, or when there is high risk of non-union. 1

Understanding Jones Fractures

• Jones fractures occur in the metadiaphyseal junction (Zone 2) of the fifth metatarsal, an area with relatively poor blood supply, making these fractures prone to delayed union and non-union 2
• MRI is useful for detecting occult Jones fractures when radiographs are negative or inconclusive 3
• These fractures differ from tuberosity avulsion fractures (Zone 1) and diaphyseal stress fractures (Zone 3) in terms of mechanism, treatment, and prognosis 4

Non-Operative Treatment with CAM Boot

• Non-operative treatment is appropriate for:

  • Non-displaced or minimally displaced Jones fractures (less than 3-4mm displacement) 1
  • Type I fractures according to Torg classification (acute fractures with sharp margins) 1
  • Non-athletic patients with lower activity demands 4

• Non-operative treatment protocol:

  • 6-8 weeks of non-weight-bearing in a CAM boot 4
  • Progressive return to weight-bearing after radiographic evidence of healing 5
  • Full recovery typically takes 8-12 weeks 5

Surgical Indications

• Surgical treatment is indicated for:

  • Displacement greater than 3-4mm or angulation more than 10 degrees 1
  • Type II fractures (delayed union with widened fracture line and sclerotic margins) in active patients 1
  • Type III fractures (non-union with complete obliteration of the medullary canal) 1
  • High-performance athletes even with acute non-displaced fractures 4
  • Patients with history of previous non-union 4

• Surgical approach:

  • Intramedullary screw fixation is the most common technique 6
  • Percutaneous approach minimizes soft tissue damage 6
  • Screw diameter typically 4.5-5.5mm based on canal size 6, 2
  • Post-operative protocol includes 2 weeks non-weight-bearing followed by progressive weight-bearing in a protective boot 6

Outcomes and Complications

• Non-operative treatment has non-union rates between 15-30% 6
• Surgical treatment has significantly lower non-union rates (0-11%) 6
• Average time to radiographic healing is approximately 6-10 weeks with surgical fixation 6
• Potential complications include:
  • Delayed union or non-union (more common with non-operative treatment) 4
  • Refracture (particularly with early return to activity) 2
  • Hardware irritation or failure 2

Clinical Pearls and Pitfalls

• The fifth metatarsal has a lateroplantar curvature where the medullary canal begins to taper, which is important to consider when selecting screw length for surgical fixation 2
• The average "straight segment" of the fifth metatarsal is about 68% of the overall length, suggesting screws should not exceed this length to avoid cortical penetration 2
• For non-operative treatment, patient compliance with non-weight-bearing restrictions is crucial for successful healing 4
• Early weight-bearing before radiographic evidence of healing increases the risk of non-union and should be avoided 4