Ankle Dislocations: Types, Causes, Diagnosis, and Management

What are the different types of ankle dislocations?

Ankle dislocations, while relatively uncommon as isolated injuries, are severe orthopedic emergencies characterized by the complete separation of the joint surfaces of the talus from the tibia and fibula. They are primarily classified based on the direction of talar displacement, often occurring in conjunction with fractures of the surrounding bones.

Understanding Ankle Anatomy and Dislocation

The ankle joint, or talocrural joint, is a highly congruent hinge joint formed by the articulation of the distal tibia and fibula (forming the ankle mortise) with the talus bone. This intricate structure, supported by strong ligaments, allows for primary movements of dorsiflexion and plantarflexion.

A dislocation refers to the complete displacement of the articulating surfaces of a joint, meaning the bones are no longer in their normal alignment. In the ankle, this means the talus is no longer correctly seated within the mortise formed by the tibia and fibula. It is crucial to distinguish a true dislocation from a sprain (ligamentous injury) or a fracture (bone break), though ankle dislocations are very frequently accompanied by fractures, leading to what is known as a fracture-dislocation.

Classification of Ankle Dislocations

Ankle dislocations are typically classified based on the direction of the talus's displacement relative to the tibia and fibula. Given the robust nature of the ankle joint, isolated dislocations without associated fractures are rare; most involve significant ligamentous disruption and/or bone fractures.

Based on Direction of Talar Displacement:

• Posterior Dislocation: This is the most common type of ankle dislocation. The talus is displaced backward (posteriorly) from the tibia. This often results from a forced plantarflexion mechanism combined with an axial load, or a direct blow to the anterior aspect of the ankle. It frequently involves fractures of the malleoli (bony prominences of the ankle).
• Anterior Dislocation: Less common than posterior dislocations, here the talus is displaced forward (anteriorly) from the tibia. This typically occurs due to extreme dorsiflexion, often with an axial load, such as falling from a height and landing on the heels, or a direct blow to the posterior ankle.
• Lateral Dislocation: In this type, the talus displaces outward (laterally) from the ankle mortise. This usually results from a severe eversion injury, where the foot is forcefully turned outward. It is almost invariably associated with fractures of the medial malleolus and/or fibula due to the significant forces required to displace the talus laterally.
• Medial Dislocation: The talus displaces inward (medially) from the ankle mortise. This is caused by a severe inversion injury, where the foot is forcefully turned inward. Similar to lateral dislocations, it is highly associated with fractures of the lateral malleolus and/or other ankle components.
• Superior Dislocation (Diastasis): This is a rare and severe injury where the talus is driven upward between the tibia and fibula, leading to a widening of the ankle mortise. This indicates a complete disruption of the tibiofibular syndesmosis (the strong ligaments connecting the distal tibia and fibula), often accompanied by a fracture of the fibula (e.g., a Maisonneuve fracture) and/or the medial malleolus. It is caused by high-energy trauma with significant axial loading.

Based on Associated Injuries:

• Isolated Dislocation: Extremely rare, meaning the talus dislocates without any accompanying bone fractures. When it occurs, it implies severe ligamentous disruption.
• Fracture-Dislocation: This is by far the most common presentation. The dislocation is accompanied by one or more fractures of the malleoli (medial, lateral, posterior), the talus itself, or the distal tibia (pilon fracture). The type of fracture often corresponds to the direction of the dislocation and the mechanism of injury.
• Open vs. Closed Dislocation:
  • Closed Dislocation: The skin remains intact over the dislocated joint.
  • Open Dislocation: The skin is broken, exposing the joint and potentially the bone, significantly increasing the risk of infection. This signifies a high-energy injury.

Common Mechanisms of Injury

Ankle dislocations are typically the result of high-energy trauma, due to the inherent stability of the ankle joint. Common mechanisms include:

• Falls from Height: Landing awkwardly on the foot, especially from significant heights.
• Motor Vehicle Accidents (MVAs): Direct impact or rotational forces applied to the ankle.
• High-Impact Sports Injuries: Such as those seen in football, basketball, gymnastics, or skiing, involving severe twisting, axial loading, or direct blows.
• Extreme Ranges of Motion with Axial Load: Forcing the ankle into extreme plantarflexion, dorsiflexion, inversion, or eversion while simultaneously bearing weight or sustaining an impact.

Clinical Presentation and Diagnosis

Individuals with an ankle dislocation will experience immediate, severe pain, often accompanied by a visible deformity of the ankle joint, rapid swelling, and an inability to bear weight. There may also be signs of nerve or vascular compromise, such as numbness, tingling, or a pale/cold foot, which constitutes a medical emergency.

Diagnosis is primarily clinical, based on the visible deformity and patient history. Imaging studies are crucial for confirming the diagnosis, identifying the direction of displacement, and, most importantly, detecting associated fractures:

• X-rays: Standard anterior-posterior (AP), lateral, and oblique views are essential to visualize the dislocation and any accompanying fractures.
• Computed Tomography (CT) Scan: Often used for complex fracture-dislocations to get a more detailed 3D view of the bone fragments and joint involvement, aiding surgical planning.
• Magnetic Resonance Imaging (MRI): May be used to assess soft tissue injuries, such as ligamentous tears or cartilage damage, once the acute dislocation has been reduced.

Management and Prognosis

Immediate management of an ankle dislocation involves prompt reduction (repositioning the bones back into alignment), which is critical to minimize complications like skin necrosis, nerve damage, or vascular compromise. This is typically performed under sedation or anesthesia.

Subsequent treatment depends heavily on whether the dislocation is isolated or, more commonly, associated with fractures:

• Non-Surgical Management: May be considered for rare, stable, isolated dislocations after reduction, involving immobilization in a cast or boot, followed by progressive rehabilitation.
• Surgical Management: Most ankle fracture-dislocations require surgical intervention to stabilize the fractured bones (Open Reduction and Internal Fixation - ORIF) and/or repair severely torn ligaments, restoring ankle joint stability and alignment.

Regardless of the initial treatment, a comprehensive rehabilitation program focusing on restoring range of motion, strength, balance (proprioception), and functional mobility is vital for optimal recovery. Prognosis varies widely depending on the severity of the initial injury, the presence and type of associated fractures, and the development of complications such as post-traumatic arthritis, chronic instability, or nerve damage.

Conclusion

Ankle dislocations are serious injuries, almost always occurring in conjunction with fractures due to the significant forces required to disrupt the ankle joint's inherent stability. Understanding their classification based on the direction of talar displacement and associated injuries is critical for accurate diagnosis and effective management. While challenging to rehabilitate, prompt and appropriate medical intervention can significantly improve outcomes for individuals experiencing these severe ankle traumas.