Is a posterior short leg plantar orthotic (PSLP) device suitable for a patient with a possible fifth metatarsal fracture and ankle sprain?

Management of Fifth Metatarsal Fracture with Ankle Sprain

A posterior short leg plantar orthotic (PSLP) device is highly recommended for patients with a possible fifth metatarsal fracture and ankle sprain, as it provides superior protection and promotes optimal healing compared to other immobilization options. 1

Diagnostic Approach

1. Apply Ottawa Ankle Rules to determine need for imaging:

   • Pain in malleolar zone with bone tenderness at posterior edge/tip of either malleolus
   • Inability to bear weight immediately and in emergency department 1

2. Obtain appropriate imaging:

   • Three-view ankle radiographs (anteroposterior, lateral, and mortise views) 1
   • Consider CT for complex fracture patterns or inconclusive radiographs
   • MRI if osteochondral injury is suspected or for persistent pain 1

3. Physical examination:

   • Delayed examination (4-5 days post-injury) optimizes sensitivity (84%) and specificity (96%) for ligament injuries 2
   • Check for hematoma and pain on palpation around distal fibula
   • Perform anterior drawer test to assess ligament integrity

Treatment Recommendations

For Fifth Metatarsal Fracture

Treatment depends on fracture location:

1. Tuberosity avulsion fracture (Zone 1):

   • Initial treatment: Controlled ankle motion (CAM) walker boot
   • Duration: 2 weeks with progressive mobility as tolerated 3
   • CAM walker boot demonstrates faster bone healing (7.2 weeks) compared to hard-soled shoes (8.6 weeks) 4

2. Jones fracture (Zone 2):

   • Requires at least 6-8 weeks in a short leg non-weight-bearing cast
   • Healing time can extend to 10-12 weeks 3
   • Consider surgical management for athletes or delayed healing

3. Shaft fracture (Zone 3):

   • Weight-bearing as tolerated in a protective boot
   • These fractures heal reliably without surgical intervention 5

For Ankle Sprain

1. Functional treatment is preferred over immobilization:

   • Early exercise therapy to recover joint functionality 2
   • Functional support (brace or tape) based on patient preference

2. Pain management:

   • NSAIDs may be used to reduce pain and swelling 2, 1
   • Multimodal analgesia including acetaminophen for breakthrough pain 1

Why CAM Walker Boot/PSLP is Preferred

1. Superior pressure reduction:

   • CAM walker boot significantly reduces peak pressure and contact pressure at the fifth metatarsal during walking and heel-walking compared to postoperative sandals and athletic shoes 6
   • This offloading is crucial for optimal fracture healing

2. Better healing outcomes:

   • Faster bone healing with CAM walker boot (7.2 weeks) versus hard-soled shoes (8.6 weeks) 4
   • Provides appropriate immobilization while allowing controlled movement

3. Addresses both injuries simultaneously:

   • Provides stability for ankle sprain while protecting the fifth metatarsal fracture
   • Allows for functional treatment approach recommended for ankle sprains 2

Follow-up Protocol

1. Clinical and radiographic follow-up at:

   • 2 weeks
   • 4-6 weeks to ensure maintained alignment and assess healing 1

2. Monitor for complications:

   • Delayed union or non-union
   • Post-traumatic arthritis
   • Persistent pain or instability 1

3. Consider referral to orthopedics if:

   • No improvement after 6 weeks of conservative treatment
   • Signs of delayed union or non-union
   • Persistent pain despite appropriate treatment 1

Important Considerations

• Ankle joint injuries frequently accompany fifth metatarsal fractures, with talocrural joint effusion (71.8%) and bone marrow edema (41.0%) being common findings 7
• Early mobilization helps prevent stiffness and promotes healing 1
• Avoid prolonged immobilization to prevent deconditioning and delayed recovery 1
• For patients with both injuries, the CAM walker boot/PSLP provides the optimal balance between protection and functional recovery