What is the treatment for a trimalleolar fracture with mild displacement and mild lateral widening of the mortise due to posterior and lateral displacement of the fibular fracture?

Treatment of Trimalleolar Fracture with Mild Displacement and Lateral Mortise Widening

Primary Recommendation

Surgical fixation with open reduction and internal fixation (ORIF) is indicated for this trimalleolar fracture, as the presence of any displacement and mortise widening indicates instability requiring operative intervention. 1, 2

Rationale for Surgical Management

The key determinants for surgical intervention in your case include:

• Displacement >2mm mandates surgical management 1
• Ankle mortise instability (medial clear space >4mm) requires surgical intervention 1, 2
• Trimalleolar fractures are inherently unstable and require surgical management 1, 3
• Lateral widening of the mortise from posterior and lateral fibular displacement confirms instability 4, 2

The American College of Radiology identifies trimalleolar fractures as having increased incidence of instability, particularly when associated with medial tenderness, bruising, swelling, or fibular fracture patterns that disrupt the syndesmosis 4, 1.

Preoperative Assessment

Before proceeding to surgery, obtain:

• Weight-bearing radiographs (if patient can tolerate) to assess dynamic instability 4, 1
• Standard three-view radiographs: anteroposterior, lateral, and mortise views 4, 1, 3
• CT imaging to evaluate the posterior malleolar fragment size, comminution, and intra-articular involvement 4, 5
• Measurement of medial clear space (>4mm confirms instability) 4, 1, 2

CT is particularly important for complex fractures to determine the extent of injury and guide preoperative planning 4.

Surgical Technique

Fixation Sequence and Approach

Anatomic reduction and stable internal fixation of all three malleoli should be achieved, with particular attention to restoring the ankle mortise and syndesmotic stability 6, 5:

1. Posterior malleolus fixation first - This provides a stable platform and increases syndesmotic stability through bone-to-bone fixation 5
2. Lateral malleolus (fibular) fixation - Restores fibular length and rotation 6, 5
3. Medial malleolus fixation - Completes mortise reconstruction 6, 5

Specific Technical Considerations

• Fragment-specific low-profile anatomical fixation implants can be used with excellent outcomes 7
• Direct posterior malleolus fixation (prone positioning) is preferred over anterior-to-posterior screw fixation for better visualization and reduction 5
• Anatomic reduction of the posterior tibial rim restores the physiological shape of the tibial incisura and facilitates fibular reduction 5
• Intraoperative verification of syndesmotic stability after fixation of all fragments 6, 5

Syndesmotic Management

After fixation of all three malleoli, only 4% of patients require syndesmotic screw placement if anatomic reduction is achieved 5. This is a critical finding:

• Fixation of anterior and posterior tibial fragments provides bone-to-bone syndesmotic stability 5
• If syndesmotic instability persists after malleolar fixation, insert syndesmotic screw 6
• Verify correct fibular positioning within tibial incisura using three-dimensional fluoroscopy or postoperative CT 6

Alternative Surgical Approach

Arthroscopically assisted reduction and minimally invasive surgery (AARMIS) is an alternative to traditional ORIF with comparable radiographic and functional outcomes 8. This technique may be considered in appropriate cases, though ORIF remains the standard approach 8.

Postoperative Protocol

• Early range of motion exercises beginning postoperative day 2 6
• Partial weight-bearing (20 kg) in cast or boot for 6 weeks 6
• Syndesmotic screw removal at 6 weeks if placed, then rapid increase in weight-bearing 6
• Mean time to union is 7.4 weeks (range 5-16 weeks) 7

Expected Outcomes

With anatomic reconstruction of the ankle mortise and articular surfaces:

• Good to excellent results in 75-89% of cases 6
• Average MOXFQ score of 34.3 and FADI score of 77.9 7
• Average Olerud-Molander Score of 79 and AOFAS score of 87 at long-term follow-up 5

Critical Pitfalls to Avoid

• Failure to achieve anatomic reduction of the distal fibula into the tibial incisura leads to poor outcomes 6
• Inadequate assessment of syndesmotic stability after malleolar fixation 6, 5
• Delayed surgical intervention increases soft tissue complications 6
• Trimalleolar fractures with dislocation at time of injury have higher rates of post-traumatic arthritis 6