Lauge-Hansen Classification of Ankle Fractures
What It Is
The Lauge-Hansen classification is a mechanism-based system for ankle fractures that categorizes injuries according to the position of the foot at the time of injury and the direction of the deforming force, predicting the sequence of ligamentous and bony injuries. 1, 2
The classification consists of four main injury patterns 1, 2:
- Supination-External Rotation (SER): Most common pattern (63% of fractures), involving external rotation force on a supinated foot 3, 1
- Pronation-External Rotation (PER): Second most common (19% of fractures), involving external rotation force on a pronated foot 3, 1
- Supination-Adduction (SA): Less common pattern involving adduction force on a supinated foot 1
- Pronation-Abduction (PA): Involves abduction force on a pronated foot 1
Each pattern progresses through predictable stages of injury, starting with ligamentous disruption and progressing to sequential bone fractures 2.
Why It's Important for Orthopaedic Surgery Residents
Diagnostic Algorithm and Treatment Planning
Understanding this classification allows you to identify occult ligamentous injuries based solely on fracture patterns visible on plain radiographs. 1, 4 The system provides a logical framework for:
- Predicting injury sequence: Each classification follows a predictable progression of ligament rupture and bone fractures 2
- Identifying hidden soft tissue damage: The fracture pattern reveals which ligaments are likely torn even without MRI 1, 4
- Planning surgical approach: Knowing the mechanism guides your operative strategy and fixation method 3
Radiographic Assessment Requirements
You need three standard ankle views (anteroposterior, mortise, and lateral) to properly classify injuries 2, 4. The diagnostic algorithm starts with:
- Assess fibular fracture location and morphology - this immediately identifies the injury type 1
- Evaluate for medial malleolar fracture - defines the stage of injury completeness 1
- Check for posterior malleolar involvement - localizes sites of ligamentous disruption 1
Critical Limitations You Must Know
The System Has Significant Predictive Failures
In 53% of ankle fractures that fit Lauge-Hansen categories, the actual ligamentous injury patterns on MRI did not match the predicted sequence. 3 This is a crucial limitation that affects treatment decisions.
Additional important caveats include:
- 17% of ankle fractures cannot be classified using this system at all 3
- Over 65% of patients have both complete ligamentous injury AND fracture of the malleolus where that ligament attaches - a "double injury" pattern not well-predicted by the classification 3
- A novel fracture pattern exists (high spiral fibular fracture, vertical shear medial malleolus, posterior malleolar fracture, complete AITFL and interosseous membrane tears) that doesn't fit any Lauge-Hansen category 3
Clinical Application Strategy
Use the Lauge-Hansen system only as a guide, not as the sole basis for treatment decisions. 3 When managing ankle fractures:
- Apply the classification to understand the likely mechanism and injury sequence 5, 2
- Recognize that 90-95% of cases can be rapidly assessed with the algorithmic approach 1
- Consider MRI when doubt exists about joint stability or soft-tissue integrity, particularly in atypical fractures where injury patterns are less predictable 3
- Use MRI to plan surgical approaches in complex cases where the standard classification fails 3
Practical Resident Takeaway
The Lauge-Hansen classification remains valuable for rapid fracture assessment and understanding injury mechanisms 1, 2, but its limitations mean you cannot rely on it to predict all ligamentous injuries or guide every treatment decision 3. Maintain a high index of suspicion for injuries that don't fit the predicted pattern, and don't hesitate to obtain advanced imaging when the clinical picture doesn't match the radiographic classification. 3