What is the treatment for a bony avulsion fragment on the talus following an inversion injury of the ankle?

Treatment of Bony Avulsion Fragment on Talus Following Inversion Injury

For a bony avulsion fragment on the talus following an inversion injury, treatment depends critically on fragment size and displacement: fragments ≥15mm or displaced >2mm require surgical fixation, while smaller, non-displaced fragments can be managed conservatively with immobilization. 1

Initial Diagnostic Workup

Standard Radiographic Assessment

• Obtain three-view ankle radiographs (anteroposterior, lateral, and mortise views) as the initial imaging study 2
• Weight-bearing radiographs should be obtained if the patient can tolerate them, as they provide critical information about fracture stability 2
• Special attention is needed because lateral talar process fractures are missed on routine radiographs 40-50% of the time 2

Advanced Imaging Requirements

• CT scan is mandatory to determine exact fragment size, displacement, comminution, and intra-articular extension 1
• MRI without IV contrast should be obtained to assess for associated cartilage abnormalities (present in 70% of ankle fractures), bone contusions, and ligamentous injuries 1
• CT is particularly important for preoperative planning when surgical intervention is being considered 2

Treatment Algorithm Based on Fragment Characteristics

Surgical Indications (Operative Fixation Required)

• Fragment size ≥15mm 1
• Any displacement >2mm 1
• Intra-articular extension with displacement 1
• Fragments with attached anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL), as motion between fragment and bone prevents spontaneous healing 3

The rationale for surgical fixation: Primary fixation prevents rotational instability and is efficient to restore function and stability, particularly because both ATFL and CFL are typically attached to the avulsion fragment 3. Nonoperative treatment of avulsion fractures does not yield satisfactory results compared to ligament ruptures 4.

Conservative Management Criteria

• Small fragments (<15mm) 1
• Non-displaced or minimally displaced (<2mm) 1
• No intra-articular extension 1

Surgical Approach Options

All-Inside Arthroscopic Repair

• Produces superior functional outcomes compared to open procedures for ATFL avulsion fractures 5
• Results in significantly higher Karlsson Ankle Functional Scores (KAFS) and Foot and Ankle Outcome Scores (FAOS) at long-term follow-up 5
• Provides minimally invasive technique with acceptable long-term functional outcomes 5

Open Reduction and Internal Fixation

• Screw fixation of the fragment to the fibula is effective for lateral fibular avulsion fractures 3
• All patients treated with primary fixation achieved clinical and radiographic stability at mean 2.4-year follow-up 3

Post-Treatment Management

For Surgical Cases

• Non-weight bearing for 6-8 weeks post-operatively 1
• Progressive weight bearing only after radiographic confirmation of adequate healing 1
• Mean follow-up shows excellent results when diagnosed and treated acutely 6

For Conservative Cases

• Immobilization with casting 4
• Close radiographic follow-up to ensure fragment position is maintained 1
• Osseous union achieved in 65% of conservatively treated avulsion fractures 4

Critical Pitfalls to Avoid

Diagnostic Errors

• High clinical suspicion is essential, particularly in children and patients over 40 years of age, where avulsion fractures are more common than ligament ruptures 4
• Avulsion fractures often present like ankle sprains, leading to missed injuries and delayed diagnosis 7
• Look for swelling inferior to the lateral malleolus in the appropriate clinical setting to avoid misdiagnosing as a lateral ankle sprain 2

Treatment Consequences of Missed Diagnosis

• Untreated avulsion fractures predictably do poorly 6
• Delayed diagnosis leads to persistent posteromedial ankle pain requiring late operative excision 6
• The three patients with missed fractures in one series achieved only fair results initially, though late excision provided significant functional improvement 6
• Prompt diagnosis and appropriate management yields reliably good outcomes 6

Special Considerations

• Passive flexor hallucis longus tendon movement may be painful with posteromedial tubercle avulsion fractures 7
• Consider obtaining a 30° external rotation lateral view radiograph to better visualize posterior talar process fractures 7
• The high incidence of old avulsion fractures found in symptomatic chronic ankle instability indicates the need for primary fixation 3