Pure Ankle Dislocation: A Rare but Important Orthopedic Injury
Ankle injuries are among the most frequent orthopedic presentations in emergency departments worldwide. However, pure ankle dislocation—a complete dislocation of the tibiotalar joint without any associated fracture—is an extremely rare event. Despite the ankle’s robust ligamentous support and the bony stability of the ankle mortise, certain extreme mechanisms of injury can lead to this unusual condition.
What Is Pure Ankle Dislocation?
Unlike typical ankle dislocations that are accompanied by malleolar fractures, pure ankle dislocation occurs when the talus is displaced from its articulation with the tibia and fibula without breaking any surrounding bones. These cases are not only rare but often misdiagnosed due to their similarity to other hindfoot injuries and the lack of specific ICD coding.
How Rare Is It?
A large-scale systematic review and hospital data audit estimated that pure ankle dislocations account for:
- Only 0.065% of all ankle injuries
- And 0.46% of all ankle dislocations
At a tertiary referral hospital with a catchment population of over 1.3 million people, only 3 confirmed cases of pure ankle dislocation were recorded in a 12-year span. Even when including possible but unconfirmed cases, the incidence was still less than 1 in a million per year.
What Causes Pure Ankle Dislocation?
Most commonly, pure ankle dislocations result from high-energy trauma, such as:
- Motor vehicle accidents
- Falls from a height
- Sports injuries, especially football, basketball, or high-impact landings
The typical biomechanical mechanism involves a combination of:
- Axial loading (a downward force through the leg)
- Plantarflexion (pointing the foot downward)
- And either inversion or eversion (twisting of the ankle inward or outward)
These forces can rupture key ligaments around the ankle without fracturing the surrounding bones.
A Case Example
One recent case involved a 22-year-old male who suffered a closed pure ankle dislocation after falling from a stair step—just one meter in height. The injury resulted in posteromedial dislocation of the talus, and MRI later showed a rupture of multiple ligaments, including the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and partial tear of the deltoid ligament, along with a small osteochondral lesion.
How Is It Diagnosed?
Initial imaging involves plain radiographs (X-rays) in both anteroposterior and lateral views to confirm the dislocation and rule out fractures.
- CT scans post-reduction help detect hidden fractures or syndesmotic widening.
- MRI can reveal soft tissue damage including ligament tears and osteochondral lesions.
Neurovascular assessment is critical before and after reduction, as approximately 19% of cases involve temporary vascular compromise.
Direction of Dislocation
Among 154 reviewed cases, the posteromedial direction was the most common (46%), followed by:
- Posterior (15%)
- Medial (20%)
- Lateral (12%)
- Other types (anterior, superior, anterolateral) were far less frequent.
This directional variability is closely tied to the injury mechanism.
Classification System (Fernandes)
Fernandes proposed a classification based on direction and mechanism:
| Type | Direction | Mechanism |
|---|---|---|
| I | Posteromedial/Medial | Axial loading, plantarflexion, internal rotation |
| II | Lateral | Axial loading, plantarflexion, external rotation |
| III | Superior | Axial loading, dorsiflexion, external rotation |
| IV | Anterior | Axial loading, plantarflexion, anterior force |
Management and Treatment
Closed Injuries
Most closed pure ankle dislocations are treated non-operatively:
- Immediate reduction under sedation
- Short leg cast immobilization (typically 6 weeks)
- Functional rehabilitation with focus on range-of-motion and peroneal strengthening
In the case described earlier, the patient began weight-bearing at 6 weeks and returned to full function by 12 months post-injury.
Open Injuries
These require more aggressive management:
- Wound debridement
- IV antibiotics
- Tetanus prophylaxis
- Possible primary or delayed ligament repair
Half of all reviewed pure dislocations were open injuries, and they showed higher complication rates—including infections (8%), stiffness (23%), and posttraumatic arthritis (14%).
Do Ligaments Need to Be Surgically Repaired?
One of the key takeaways from the literature is that surgical ligament repair does not significantly alter outcomes. In a large review, only 2.7% of patients had ankle instability after treatment—regardless of whether ligament repair was performed.
The consensus is that ligament repair should only be considered in cases of chronic instability, not as a routine primary intervention.
Outcomes and Prognosis
The outlook for patients is generally excellent:
- 59% of patients reported no symptoms after treatment
- 18% experienced ankle stiffness
- 10% developed arthritis
- Only 2.7% had lasting instability
Patients with closed injuries fare better than those with open dislocations. Additionally, early weight-bearing and shorter immobilization (2–3 weeks) may reduce stiffness without increasing instability.
Recommendations for Clinicians
For Closed Injuries:
- Immediate reduction
- Short leg cast (2–6 weeks)
- Begin functional rehab early
For Open Injuries:
- Emergency reduction
- Surgical debridement per Gustilo-Anderson classification
- Consider syndesmosis fixation if required
- Avoid unnecessary ligament repair unless instability persists
Conclusion
Pure ankle dislocation is a rare but significant orthopedic injury. Awareness of this condition is essential for prompt diagnosis and management. The evidence suggests that conservative treatment, when applied properly, leads to excellent functional outcomes in most cases—especially in closed injuries.
While surgery may be required in open injuries or cases of neurovascular compromise, routine ligament repair is generally unnecessary. Early recognition, appropriate imaging, and structured rehabilitation are the cornerstones of successful recovery.
Do you have more questions?
Q. What is an ankle dislocation?
A. An ankle dislocation occurs when the bones that form the ankle joint are forced out of their normal alignment.
Q. What usually causes an ankle dislocation?
A. An ankle dislocation is typically caused by a high-energy trauma, such as a car accident, fall, or sports injury.
Q. Can an ankle dislocation occur without a fracture?
A. Most ankle dislocations are associated with fractures, but they can rarely occur without one.
Q. What are the symptoms of an ankle dislocation?
A. Symptoms include severe pain, visible deformity, swelling, inability to bear weight, and bruising.
Q. How is an ankle dislocation diagnosed?
A. Diagnosis is confirmed through a physical exam and imaging studies, typically X-rays or CT scans.
Q. What is the immediate treatment for an ankle dislocation?
A. The immediate treatment involves realigning the bones, a procedure called reduction, followed by immobilization.
Q. Is surgery required for ankle dislocations?
A. Surgery is often required, especially if the dislocation is associated with fractures or if the joint is unstable.
Q. How long does it take to recover from an ankle dislocation?
A. Recovery time can vary but typically takes several months and may include physical therapy.
Q. Can ankle dislocations lead to long-term complications?
A. Yes, complications such as chronic pain, joint stiffness, instability, and arthritis can occur.
Q. What kind of rehabilitation is needed after an ankle dislocation?
A. Rehabilitation may involve physical therapy to restore strength, flexibility, and range of motion.
Q. Are there any risks associated with untreated ankle dislocations?
A. Yes, untreated dislocations can lead to poor healing, permanent deformity, and loss of joint function.
Dr. Mo Athar
