Ankle Fractures: Lauge-Hansen Classification, Weber Classification

Epidemiology and Mechanism of Injury

Ankle fractures represent a significant portion of orthopedic injuries, occurring at an incidence of 187 per 100,000 adults annually. The injury demonstrates a bimodal distribution:

• Young Adults (15-24 years): High-energy mechanisms such as sports or vehicular accidents.
• Elderly Adults (75-84 years): Low-energy mechanisms, typically falls, often associated with osteoporosis.

Anatomy of the Ankle Joint

Understanding the complex anatomy of the ankle joint is critical for accurate diagnosis and surgical management:

• Bones:
  • Tibia: Medial malleolus, posterior malleolus, and the tibial plafond (distal tibial articular surface).
  • Fibula: Lateral malleolus.
  • Talus: Bears the body's weight and articulates with the tibial plafond and the medial and lateral malleoli.
• Ligaments:
  • Deltoid Ligament: Medial stabilizer, consisting of superficial and deep components. The superficial layer resists eversion, and the deep layer resists external rotation.
  • Lateral Ligament Complex: Composed of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL), which stabilize against inversion.
  • Syndesmotic Complex: Includes the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), interosseous ligament (IOL), interosseous membrane, and inferior transverse ligament (ITL).

Classification Systems

Accurate classification of ankle fractures guides management decisions and prognostication:

1. Lauge-Hansen Classification

The Lauge-Hansen classification system is based on the mechanism of injury and describes both the position of the foot at the time of the injury (supination or pronation) and the direction of the deforming force (adduction, abduction, or external rotation). This system is valuable for understanding the sequence of ligamentous and osseous injuries.

Supination-External Rotation (SER)

• Stage 1: Injury to the anterior talofibular ligament (ATFL), resulting in sprain or rupture.
• Stage 2: Oblique or spiral fracture of the distal fibula, starting at the anteroinferior and extending posterosuperiorly.
• Stage 3: Rupture of the posterior talofibular ligament (PTFL) or an avulsion fracture of the posterior malleolus.
• Stage 4: Transverse fracture of the medial malleolus or disruption of the deltoid ligament.

SER is the most common ankle fracture pattern and typically results from a twisting mechanism (e.g., during sports). It starts with ligamentous injuries and progresses to involve the fibula and potentially the medial side of the ankle.

Pronation-Abduction (PAB)

• Stage 1: Rupture of the deltoid ligament or transverse fracture of the medial malleolus.
• Stage 2: Rupture of the anterior inferior tibiofibular ligament (AITFL).
• Stage 3: Comminuted or transverse fracture of the fibula above the level of the syndesmosis.

PAB injuries are often high-energy injuries, leading to a more complex fibular fracture and higher risk of syndesmotic injury.

Pronation-External Rotation (PER)

• Stage 1: Rupture of the deltoid ligament or transverse fracture of the medial malleolus.
• Stage 2: Rupture of the AITFL.
• Stage 3: Spiral or oblique fracture of the fibula above the level of the syndesmosis.
• Stage 4: Rupture of the PTFL or avulsion fracture of the posterior malleolus.

PER injuries are often more severe and typically involve disruption of both the medial and lateral structures, as well as the syndesmosis.

Supination-Adduction (SAD)

• Stage 1: Transverse fracture of the distal fibula or rupture of the lateral ligament complex (ATFL, CFL).
• Stage 2: Vertical fracture of the medial malleolus due to compression or impaction.

SAD fractures are less common and involve a combination of ligamentous injury and compression fractures, which occur when the foot is forcibly inverted.

2. Weber Classification (Danis-Weber Classification)

The Weber classification system is based on the location of the fibular fracture in relation to the syndesmosis (the ligamentous connection between the distal tibia and fibula). This system helps determine fracture stability and the need for operative management.

Weber Type A (Infrasyndesmotic)

• The fracture is located below the level of the syndesmosis, typically resulting from a low-energy injury.
• Syndesmosis: Intact.
• Mechanism: Most often related to supination-adduction (SAD).
• Stability: Generally stable fractures, as the syndesmosis remains intact.
• Management: Frequently treated non-operatively with immobilization if the fracture is non-displaced.

Weber Type B (Transsyndesmotic)

• The fracture occurs at the level of the syndesmosis, often with some degree of syndesmotic involvement.
• Syndesmosis: May be partially injured, and a stress test (manual or gravity stress) may be required to assess stability.
• Mechanism: Commonly associated with supination-external rotation (SER) injuries.
• Stability: Potentially unstable, depending on the extent of syndesmotic disruption.
• Management: Often requires operative fixation, especially if the syndesmosis is disrupted or if there is significant displacement.

Weber Type C (Suprasyndesmotic)

• The fracture is located above the level of the syndesmosis, frequently involving the proximal fibula.
• Syndesmosis: Disrupted, with a high likelihood of instability.
• Mechanism: Typically results from pronation-external rotation (PER) injuries.
• Stability: Unstable fractures due to syndesmotic injury.
• Management: Requires surgical fixation, including syndesmotic fixation if indicated.

Weber Type C fractures are often more severe, as they involve higher levels of energy and disruption to both osseous and ligamentous structures.

3. AO/OTA Classification

The AO/OTA classification system provides a more detailed and standardized method for categorizing fractures based on the location of the fracture and the degree of comminution. It is widely used in trauma settings for more comprehensive documentation.

Type 44A (Infrasyndesmotic)

• Fractures are located below the syndesmosis, corresponding to Weber A fractures.
• Subtypes:
  • 44A1: Isolated lateral malleolus fracture.
  • 44A2: Isolated medial malleolus fracture.
  • 44A3: Bimalleolar fracture without syndesmotic involvement.

Type 44B (Transsyndesmotic)

• Fractures occur at the level of the syndesmosis, corresponding to Weber B fractures.
• Subtypes:
  • 44B1: Lateral malleolar fracture with partial syndesmotic involvement.
  • 44B2: Bimalleolar fracture with syndesmotic involvement.
  • 44B3: Bimalleolar-equivalent fracture (lateral malleolus fracture with medial ligament injury).

Type 44C (Suprasyndesmotic)

• Fractures are located above the syndesmosis, corresponding to Weber C fractures, and are associated with syndesmotic disruption.
• Subtypes:
  • 44C1: Simple fibular fracture above the syndesmosis with associated syndesmotic injury.
  • 44C2: Complex fibular fracture with significant syndesmotic disruption.
  • 44C3: Trimalleolar fracture with posterior malleolar involvement.

The AO/OTA classification is more comprehensive in grading the complexity of the fractures, particularly in differentiating between simple and complex patterns and providing a structured approach to decision-making regarding operative fixation.

Clinical Assessment

A comprehensive assessment includes history, physical examination, and imaging:

• History: Mechanism of injury, previous ankle injuries, patient activity level, and any coexisting conditions that may affect management (e.g., diabetes, peripheral vascular disease).
• Physical Examination: Inspection for deformity, swelling, and ecchymosis. Palpation of bony landmarks to assess for tenderness, and neurovascular examination to evaluate distal pulse, capillary refill, and sensory function.
• Special Tests: Check for Maisonneuve fracture with proximal fibula tenderness, deltoid ligament competence with medial tenderness, and syndesmotic injury using the squeeze and external rotation stress tests.

Radiographic Evaluation

• Standard Views: Ankle series (AP, lateral, and mortise views) to assess fracture location, displacement, and involvement of the syndesmosis.
• Stress Radiographs: Manual or gravity stress views are crucial for evaluating deltoid ligament integrity and detecting occult syndesmotic injuries.
• CT Scanning: Provides detailed assessment of fracture anatomy, particularly for complex fractures like trimalleolar or comminuted fractures, and aids in surgical planning.
• MRI: Useful in evaluating soft tissue injuries, including ligamentous damage or chondral injuries, especially in cases of persistent pain or unclear diagnosis.

Management Strategies

Management decisions are based on fracture stability, displacement, and patient factors (activity level, comorbidities):

1. Nonoperative Management:
   • Indications: Non-displaced fractures, stable ankle mortise, and patients unfit for surgery.
   • Treatment: Immobilization with a short-leg cast or functional brace, non-weight bearing for 4-6 weeks, followed by gradual rehabilitation.
2. Operative Management:
   • Indications: Displaced fractures, unstable ankle mortise, bimalleolar or trimalleolar fractures, syndesmotic disruption, open fractures, and fractures associated with other injuries.
   • Surgical Techniques:
     • Open Reduction and Internal Fixation (ORIF): Standard approach for most unstable or displaced fractures. Goals include anatomical reduction of the articular surface, restoration of limb alignment, and stable fixation to allow early mobilization.
       • Medial Malleolus: Fixed with lag screws or tension band wiring for vertical fractures.
       • Lateral Malleolus: Fixed with plate and screws, typically a one-third tubular or locking plate; posterior antiglide plating can provide superior biomechanical stability for oblique fractures.
       • Posterior Malleolus: Fixed if >25% of the articular surface is involved or if there is >2mm displacement; fixation options include direct screws or buttress plating.
       • Syndesmotic Injuries: Addressed with screws or suture-button devices, depending on the extent of diastasis and stability after fixation of malleolar fractures.
     • External Fixation: Employed as a temporary measure in severely contaminated open fractures or when soft tissue conditions preclude immediate ORIF. Definitive fixation follows once soft tissue conditions improve.

Postoperative Care and Rehabilitation

• Early Mobilization: Essential to prevent stiffness and maintain joint range of motion. Weight-bearing status is determined based on fracture stability and fixation.
• Complication Monitoring: Regular follow-up to identify complications such as wound infections, nonunion, malunion, post-traumatic arthritis, and hardware-related problems.
• Physical Therapy: Initiated to restore strength, proprioception, and functional mobility, tailored to individual patient recovery.

Complications

• Early Complications: Include infection (especially in open fractures), compartment syndrome, and wound dehiscence.
• Late Complications: Can involve nonunion or malunion, post-traumatic arthritis, syndesmotic malreduction, hardware failure or irritation, and chronic pain.

Conclusion

Ankle fractures require a systematic approach to diagnosis and management, incorporating detailed anatomical knowledge, classification understanding, and tailored surgical techniques. Optimizing outcomes involves not only technical proficiency in fracture fixation but also vigilant postoperative care and patient-specific rehabilitation strategies.