Ankle Dislocation


Introduction

Ankle dislocations are a relatively common type of dislocation encountered in the emergency department. They exist in two forms: 

  1. a true dislocation without fracture
  2. a fracture-dislocation, occurring in the vast majority [1]

The ankle joint complex is composed of three main articulations: talocalcaneal (subtalar), transverse-tarsal (talocalaneonavicular) and the tibiotalar (talocrural) joints. The true ankle joint is the tibiotalar joint (between the tibia, fibula and the talus). It is a ring-like structure with the ability to plantarflex and dorsiflex 40° and 20° respectively in the sagittal plane. It is a hinge joint. Below the ankle, at the subtalar joint (joint between the talus and calcaneus), the foot can typically invert 23° and evert about 12° in the frontal plane. The transverse tarsal joint (Chopart’s joint) is the junction between the talus and navicular bone. Because they share a common axis of motion, the transverse tarsal joint and the subtalar joint are considered part of the same functional unit with the motions of inversion and eversion. The combination of these joints gives the foot the ability to compensate for the loads placed during walking and other activities.

The human ankle maintains this range of motion under extremely heavy loads and can support several times the human body weight for short periods. Because of the stress placed on the ankle as one pushes off in different directions, it is possible to dislocate it by exceeding the ligamentous strength that encloses the ankle.

The stability of the joint is maintained through three groups of ligaments: the tibiofibular syndesmosis, the deltoid ligament, and the lateral collateral ligaments. The tibiofibular syndesmosis limits motion between the tibia and fibula and is composed of the anterior tibiofibular ligament, posterior tibiofibular ligament, and the interosseous tibiofibular joint. The deltoid ligaments support the medial ankle and aid in resisting eversion. The lateral collateral ligaments (including the anterior and posterior talofibular ligaments and the calcaneofibular ligament) act to resist inversion. Usually, the ligaments are so strong that the bones give way and create a fracture-dislocation.[2]

Etiology

The mechanism of the ankle dislocation depends on whether it is associated with a fracture or not. A pure ligamentous dislocation has been reported to occur in multiple directions and by multiple mechanisms.[3] The most common injury pattern occurs when the ankle is maximally plantar-flexed with an axial load and forced inversion of the foot.[4] This mechanism allows for anterior extrusion of the talus through the mortise and predisposes the ankle to damage and rupture of the anterior talofibular and calcaneofibular ligaments, leading to a posteromedial dislocation which is the most common direction of dislocation in pure ankle dislocation. Cadaveric studies by Fernandes recreated this injury by placing the foot in maximum plantar flexion with stress applied into inversion or eversion. This subsequently resulted in a medial or lateral ankle dislocation without fracture and damage to the anterior talofibular and calcaneofibular ligaments.[3][5][3] Superior dislocation usually results when an everted foot is dorsiflexed. This leads to rupture of the tibiofibular syndesmosis which in turn causes dislocation of the ankle joint superiorly.[1]  Predisposing factors that have been reported include weakness of the peroneal muscle, previous strains, ligamentous laxity, and shortness of the medial malleolus.[6][3]

The more common ankle fracture-dislocation occurs via similar mechanics as non-dislocated ankle fractures. The most likely resulting fractures, bimalleolar and trimalleolar, often result from an abduction force and displacement of the talus which is how the ankle appears to be dislocated at the time of evaluation. Sometimes these dislocations will spontaneously reduce, leaving a malleolus fracture. These resulting ankle fractures are often classified according to the Lauge-Hansen classification system[7] which includes four types based on the position of the foot and direction of the force. The four types include supination-adduction, supination-external rotation, pronation-abduction, and pronation-external rotation. Each of these types has a characteristic type of malleolar fracture, however, the intra-observer and inter-observer reliability of this classification system have been called into question in the literature.[8][9]

Epidemiology

A pure ankle dislocation without a concomitant fracture is exceedingly rare. The estimated incidence of pure ankle dislocation occurs in about 0.065% of the presentations of all ankle injuries, which includes soft tissue injuries of the ankle. This amounts to about 0.5% of all ankle dislocations, with over 99% being fracture-dislocations (of note, the incidence of this injury may be underrated given the chance of ankle reduction in the community without hospital involvement).[1] Tibiotalar dislocations have been shown to occur concomitantly in 21-36% of ankle fractures.[10][11] The injury most commonly occurs in males (72%) and is usually secondary to sporting accidents (31%) or motor vehicle accidents (30%). The direction of the dislocation is most commonly posteromedial (46%).[1]

Rarely, irreducible ankle fracture-dislocations may be encountered due to the interposition of soft tissue or fracture fragments. The “Bosworth Fracture” has been described and occurs when the proximal fibular shaft is locked behind the tibia. This type of injury is often missed on plain x-rays and is not amenable to a closed reduction in the emergency department.[12]

History and Physical

Frequently, the patient will present with a dislocated foot relative to the tibia. All of these injuries will benefit from appropriate analgesia and rapid realignment of the foot and ankle to proper anatomic position. If this is not done relatively quickly, the resulting skin breakdown and formation of fracture blisters can then lead to loss of skin coverage of the joint and permanent disability. After attending to other life-threatening injuries following the usual trauma protocols, an ankle dislocation should be reduced, preferably with procedural sedation, although an intra-articular block may be sufficient. Salen et al performed a study in which ankle dislocations were among the most common type of dislocation requiring procedural sedation.[13] While it may be quick to reduce, it is imperative to understand the significant pain that the patient will likely be experiencing and to administer appropriate analgesia before any manipulation. Be aware that the vast majority of these injuries, particularly those with open fractures, will require operative intervention. An orthopedic consultant should be notified of any open fracture, dislocation with vascular or sensory compromise, bimalleolar fracture, trimalleolar fracture, syndesmotic disruption, or pilon fractures (distal tibial impaction). 

On examination, it is important to note the direction of the foot relative to the ankle mortise, the presence/absence of the dorsalis pedis and posterior tibial pulses, capillary refill of the distal foot, other associated injuries of the foot, and localizing areas of tenderness and swelling. The sensory exam should include the dorsum of the foot, lateral and medial aspects of the foot, and sensation just proximal to the great and second toe, the area of the innervation of the deep peroneal nerve. The examiner should also note the ability to flex and extend the toes. These important physical exam findings should be documented before and after the manipulation of the foot.[14]

Evaluation

Plain x-rays should be obtained of both the ankle and tibia-fibula before an attempted reduction maneuver. Three views of the ankle should be obtained including anteroposterior (AP), lateral, and Mortise views. The Mortise view is obtained by aiming the x-ray beam in an AP direction while internally rotating the ankle 15 degrees. Obtaining full-length tibia-fibula x-rays are imperative to identify Maisonneuve-type injuries (transfer of energy through the interosseous membrane resulting in a proximal fibula fracture or proximal tibiofibular joint dislocation).

Occasionally, reduction may be necessary before imaging is obtained in the case of skin tenting or neurovascular compromise, however, Hastie et al. observed a significantly higher rate of need for re-manipulation (44% before x-ray vs. 18% after x-ray; p=0.03).[15]

In the case of a pilon-type fracture, a CT scan may be warranted. An orthopedic surgeon should be consulted before a CT scan because if the fracture requires temporizing external fixation, the CT should be obtained after this is completed for proper preoperative planning.

Differential Diagnosis

The existence of an ankle dislocation or fracture-dislocation is evident upon physical exam and noting the position of the foot relative to the tibial crest and patella is central to making the correct diagnosis. A subtalar dislocation can occur independently or in conjunction with an ankle dislocation or fracture-dislocation. These injuries in isolation can be mistaken for an ankle dislocation on a physical exam, however, plain films will show a reduced tibiotalar joint. Higher energy mechanisms can also result in total talus extrusion (tibiotalar and subtalar dislocations). This injury is also identified on plain radiographs and requires immediate orthopedic consultation.

Prognosis

For pure ankle dislocations, the overall prognosis is favorable. In a systematic review of pure ankle dislocation, Wight et al. found that the majority of patients were asymptomatic after appropriate treatment. Those who were symptomatic (primarily female) complained of stiffness or post-traumatic arthritis. Closed dislocations were associated with fewer symptoms than those with open dislocations. Prognostic factors that have been associated with worse outcomes include advanced age, presence of vascular injury, delay to reduction, and inferior tibiofibular ligament injury.[1]  Late complications that have been reported include stiffness, degenerative changes, joint instability, and capsular calcification.[6]  

The prognosis for ankle fracture-dislocation is variable. When compared to non-dislocated ankle fractures, ankle fracture-dislocations have worse long-term outcomes. SER and PER ankle fracture-dislocations were found to have significantly poorer results on the Foot and Ankle Outcome Score (FAOS) as measured by increased pain and decreased activities of daily life.[26][27] A recent study by Pincus et al. demonstrated a higher rate of ORIF revision for ankle fracture-dislocations as compared to the non-dislocated group (OR, 1.82; CI, 1.26-2.6).[28] Evidence of post-traumatic osteoarthritis of the ankle (PTOA) has been reported in up to 63% of patients sustaining an ankle fracture-dislocation.[11] Factors contributing to this result include the type of fracture, sex of the patient, and accuracy of reduction. In the earliest and largest prospective study on ankle fracture-dislocations (as described below), an "excellent" to "good" outcome was found in 82% of patients evaluated after a 2-6 year follow up.[29]

Complications

The outcome and complication rate after an ankle dislocation or fracture-dislocation is multifactorial. Complications most commonly include infection, malunion or nonunion, skin necrosis and post-traumatic arthritis. Factors that can influence a patient’s outcome include the mechanism of injury, fracture type, open fractures, and medical comorbidities. Higher energy mechanisms are more likely to result in more severe fracture patterns and open fractures.

Open injuries carry a high rate of deep infection (8%) and skin necrosis (14%) after immediate fixation.[30]  Surgical-site infection after fixation was shown by Thangarajah et al. [31] to be higher in patients who smoke and those with bimalleolar fractures, however not all of these injuries were fracture-dislocations. Complications include malunion, wound healing issues, and deep infection. These are seen at a higher prevalence in diabetics with ankle fractures treated both operatively and non-operatively, with a rate as high as 42% in diabetic patients compared to a matched cohort of nondiabetic patients in a report by McCormack et al.[32]

Lindsjo et al.[29] conducted the largest and earliest prospective study of 306 ankle fracture-dislocations who underwent operative fixation and followed them for up to 6 years after surgery. The author reported an infection rate of 1.8% and post-traumatic arthritis (PTOA) rate of 14%, however more recent studies have reported a PTOA rate of up to 63%.[11]

Deterrence and Patient Education

After proper ankle reduction and immobilization in the emergency department setting, patients should be educated on several factors.  The patients should be provided with crutches or a walker and instructed to be non-weight bearing on the injured extremity.  The patient should be able to demonstrate that they understand and can follow these restrictions.  The patient should understand that if they were to weight bear, they risk re-displacement of their fractures or dislocation.  Patients should also be educated on splint management, most importantly, not to get the splint wet as this affects the integrity of the immobilization and can cause skin problems.  If their splint does get wet, they should return to have it changed.  The patient should be educated on proper pain management including Tylenol and NSAIDs as the first line, and if they are given a narcotic prescription to only use it as needed.

Patients should also be educated on the signs and symptoms of compartment syndrome.  While compartment syndrome is rare after ankle fracture-dislocations or pure dislocations[33][34], it can be a devastating complication.  Signs and symptoms include increasing pain that is unable to be controlled with pain medication, change in color of the toes to white or blue (representing vascular compromise), increased pain with passive extension of the toes, loss of pulses and decreasing sensation in the foot and toes.   If the patient displays these signs or symptoms they should immediately return to the emergency department.

If the patient does undergo surgical fixation, patients are again educated on all of the above factors, as well as general post-anesthesia guidance.   Special attention is given to keeping the splint dry for wound-healing purposes in addition to the above-mentioned reasons. 

Enhancing Healthcare Team Outcomes

Initial management that is required of the emergency medicine physician includes prompt recognition and management of an ankle dislocation. As stated previously, the exam should at a minimum include a neurovascular status of the affected leg along with full-body assessment for concomitant or distracting injuries. Unless a neurovascular compromise is suspected, x-rays should be obtained to rule out other mimics including tibial fractures and/or subtalar dislocations (if a neurovascular compromise is suspected, an x-ray should not delay attempts at an immediate closed reduction). While this is occurring, it is the role of nursing to obtain IV access, administer appropriate analgesia and start preparing for conscious sedation or intra-articular hematoma block.

Closed reduction can be performed by either the emergency medicine provider, podiatry or orthopedic specialists, however, it has been shown that orthopedic surgeons have higher rates of success on the first attempt as compared to emergency physicians.[16]  It is the responsibility of all parties to be well versed in reduction techniques and the proper splint that should be applied. Orthopedic consultation timing is dependent on the level of familiarity/comfort of the emergency medicine provider in regard to the treatment of these injuries.  If the emergency medicine provider is not comfortable with reduction techniques, an orthopedic specialist should be contacted upon diagnosis of the injury.  If an acceptable reduction is obtained by the emergency medicine provider, the orthopedist may or may not be notified depending on the environment and culture of that particular practice.  Orthopedic specialists should always be consulted in the case of neurovascular compromise, open injuries, irreducible injuries and injuries in which concomitant compartment syndrome is suspected. Orthopedic specialists should be immediately available in the event that any of these cases arise.  

Patients should also have easy access to orthopedic follow-up and an emergency phone number to call in case of questions or concerns after being discharged from the emergency department.  Patients may have issues with their splint or issues with pain that may need to be addressed urgently and they should have easy access for these problems to be addressed.  There should also be coordination with the emergency department and orthopedic follow-up in which patients can be referred to the orthopedic specialist and be seen within one to two weeks of injury.  Some orthopedic clinics will have "fracture clinic" or "fracture appointments" which are times set aside for acutely injured patients so that, in a case of a busy orthopedic practice, these patients are not put on the same waiting list for appointments as elective patients.  


Article Details

Article Author

Ashleigh Frank

Article Editor:

Kimberly Groen

Updated:

9/22/2020 8:53:38 PM

PubMed Link:

Ankle Dislocation

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