What are the indications for operative fixation of a lateral malleolus (outer ankle bone) fracture?

Indications for Operative Fixation of Lateral Malleolus Fractures

Operative fixation of lateral malleolus fractures is indicated when there is displacement >2mm, ankle mortise instability (medial clear space >4mm), or when the fracture is part of an unstable bimalleolar or trimalleolar pattern. 1, 2

Absolute Indications for Surgery

Displacement Criteria

• Any displacement >2mm mandates surgical management to prevent long-term complications such as post-traumatic arthritis 1
• Lateral malleolus fractures associated with medial clear space widening >4mm indicate deltoid ligament disruption and require operative intervention 1, 2

Instability Patterns

• Bimalleolar fractures (lateral malleolus + medial malleolus or deltoid ligament injury) are inherently unstable and require surgical fixation 1, 2
• Trimalleolar fractures (including posterior malleolus involvement) have increased instability and mandate operative treatment 1, 2
• Lateral mortise widening from posterior and lateral fibular displacement confirms instability requiring surgery 1

Associated Injuries

• Displaced lateral malleolus fractures occurring with ipsilateral spiral tibial shaft fractures require open reduction and internal fixation of the malleolar component 3
• Syndesmotic disruption patterns (Weber C fractures above the syndesmosis) typically require operative stabilization 1

Critical Assessment Steps

Radiographic Evaluation

• Obtain standard three-view ankle radiographs (anteroposterior, lateral, and mortise views) to assess displacement and joint alignment 2
• Weight-bearing radiographs, if the patient can tolerate them, are critical for assessing dynamic instability—the most important criterion determining treatment approach 1, 2
• Measure the medial clear space on mortise view; >4mm confirms instability 1, 2

Advanced Imaging

• CT imaging should be used when evaluating complex fracture patterns, particularly to assess posterior malleolar fragment size, comminution, and intra-articular involvement 2

Relative Indications

Patient-Specific Factors

• Active, independent patients with displaced fractures benefit from anatomic reduction to optimize long-term function 1, 2
• Patients with soft tissue compromise may still require fixation but benefit from minimally invasive techniques such as intramedullary fibular nailing 4, 5

Fracture Pattern Considerations

• Weber B fractures at the syndesmotic level require careful assessment; those with medial tenderness, bruising, swelling, or mortise widening indicate instability requiring surgery 1
• Weber C fractures (above the syndesmosis) typically disrupt the syndesmosis and require operative fixation 1

Common Pitfalls to Avoid

• Do not overlook associated medial-sided injury: Lateral malleolus fractures with point tenderness over the medial malleolus or deltoid ligament suggest bimalleolar equivalent injuries requiring surgery even if the medial malleolus appears intact radiographically 1
• Examine joints above and below the fracture: Associated displaced malleolar fractures in tibial shaft injuries may be indiscernible on standard views and require focused ankle radiographs 3
• Avoid relying solely on non-weight-bearing radiographs in ambulatory patients, as dynamic instability may only be apparent with weight-bearing views 1, 2

Surgical Timing

• Hemodynamically stable patients can proceed with definitive fixation within 24 hours of injury 2
• Early mobilization and physical therapy should begin once adequate healing is confirmed to prevent stiffness 2
• Serial radiographs are essential to confirm maintenance of reduction and assess healing progression 2