Ankle Fracture Case File
Eugene C. Toy, MD, Andrew J. Rosenbaum, MD, Timothy T. Roberts, MD, Joshua S. Dines, MD
CASE 12
A 26-year-old man presents to the emergency department complaining of right ankle pain, swelling, and an inability to walk after twisting his ankle in a soccer tournament. He remembers making a quick cut before experiencing sharp pain and hearing a “crack” while falling to the ground. Physical exam reveals a swollen and ecchymotic right ankle with tenderness directly over the medial and lateral malleoli and over distal fibular at the level of the ankle joint. His skin is swollen, but intact. He is neurovascularly intact and has a strong dorsalis pedis pulse. Examination of the proximal leg is unremarkable. He has no past medical history. Figure 12–1 shows (A) anteroposterior (AP), (B) lateral, and (C) mortise radiographs of the right ankle.
Figure 12–1. (A) AP, (B) lateral, and (C) mortise radiographs of the right ankle. (Courtesy of Timothy
T. Roberts, MD)
► What is the most likely diagnosis?
► What is your next step in the management of this injury?
ANSWER TO CASE 12:
Ankle Fracture
Summary: A 26-year-old man suffered an acute twisting injury to his right ankle, resulting in pain, swelling, and an inability to bear weight.
- Most likely diagnosis: Fractures of both the lateral and medial malleoli, together known as a bimalleolar ankle fracture.
- Next step in management of injury: Administration of analgesia, systemic and/or intraarticular, and attempted closed reduction. Depending on the degree of swelling, the patient may be cast or splinted.
ANALYSIS
Objectives
- Know the clinical presentation, physical examination findings, and appropriate initial management of ankle fractures.
- Know which radiographic studies to order and how to evaluate them.
- Be familiar with the classification systems used to describe ankle fractures and recognize how different mechanisms of injury produce predictable fracture patterns.
- Have a basic understanding of stable versus unstable ankle fractures.
Considerations
This patient presented with a twisting injury that resulted in ankle pain, swelling, and an inability to bear weight. Ankle fractures tend to occur in predictable patterns, depending on the magnitude and direction of force and the position of the foot during injury. Common ankle fracture classification schemes are derived from mechanisms of injury, and thus obtaining a careful history is helpful to understanding and treating the injury. Physical examination should include a visual inspection of the skin to rule out an open injury, to evaluate swelling or blistering, and to evaluate for signs of displacement or dislocation. A full neurovascular evaluation of the foot and ankle is mandatory.
In addition to ankle pain and swelling, this patient has tenderness over both medial and lateral malleoli and cannot bear weight—3 signs that are suggestive of fracture rather than ligamentous sprain. X-rays should therefore be ordered. The most common initial radiographic study is a 3-view ankle series. Given this patient’s closed, minimally displaced bimalleolar fracture, casting or splinting (splinting is used in the setting of significant swelling or blistering) is the most appropriate next step.
APPROACH TO:
Ankle Fracture
DEFINITIONS
LATERAL MALLEOLUS: The distal portion of the fibula that articulates with the talus and provides lateral stability to the ankle joint.
MEDIAL MALLEOLUS: The distal medial projection of the tibia that articulates with the talus and provides medial stability to the ankle joint.
TIBIAL PLAFOND: The distal weightbearing articulating surface of the tibia that, together with both malleoli, comprise the mortise.
MORTISE: The bony arch formed by the articulation between malleoli and the plafond, which serves to constrain the wedge-shaped talus and allows the hinge-like motion of the ankle.
SYNDESMOSIS: This describes the ligamentous complex connecting the distal fibula and tibia. It helps stabilize the ankle mortise.
CLINICAL APPROACH
Anatomy
The ankle is a complex hinge joint consisting of articulations between the distal tibia, the distal fibula, and the talus that are held in place by a complex ligamentous system. The lateral malleolus forms the lateral portion of the ankle joint and is surrounded by the strong tibiofibular ligament complex and the syndesmotic ligament complex. These ligament structures prevent the distal tibia from separating from the fibula and provide the majority of ankle stability in external rotation. Distally on the lateral side of the ankle, the talofibular and calcaneofibular ligaments provide resistance to inversion and anterior translation of the talus. The anterior talofibular ligament is the most commonly injured ligament in ankle sprains. On the medial side, the medial malleolus is the origin of the deltoid ligament, which provides medial ligamentous support to the ankle and is the primary medial stabilizer against lateral displacement of the talus.
Examination
Clinical evaluation of a suspected ankle fracture is necessary to ensure accurate diagnosis. First, this should include a description of the mechanism of injury. This provides insight into the position of the ankle and the forces acting on it at the time of injury. Obtaining a thorough medical history is essential, as comorbidities such as additional injuries, obesity, hypercoagulable states, diabetes, and peripheral vascular disease may affect treatment options. Evaluate the extremity closely for skin punctures or lacerations that may communicate with the ankle joint or with fracture fragments. Both open joints and open fractures are considered surgical emergencies and should be treated accordingly. An obvious deformity may represent a dislocation; reduction should be performed as soon as safely possible. As always, a complete circulatory and neurologic evaluation should be performed and clearly documented.
Radiographic Evaluation
After examining a patient, one must decide whether radiographs are needed for further evaluation. The Ottawa Ankle Criteria can aide in this process. The criteria state that x-rays should be ordered if there is malleolar tenderness and:
- Bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus, or
- Bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus, or
- An inability to bear weight both immediately and in the emergency department for more than 4 steps
This algorithm demonstrates a sensitivity of nearly 100% for detecting ankle fractures and may reduce unnecessary x-ray exposure by up to 40%.
When appropriate, radiographic evaluation of the ankle should consist of a 3-view ankle series. This includes an AP view, a mortise view (oblique), and a lateral view. The mortise view is important for evaluation of the joint space. It is obtained by internally rotating the affected extremity 15 degrees on an AP view so that the x-ray beam becomes perpendicular to the transmalleolar axis. In a normal ankle, the mortise should show a smooth, evenly spaced gap between the plafond and malleoli and the talus ( Figure 12–2A ). This view is useful to determine the stability of the ankle based on several measurements. The first is the medial clear space ( Figure 12–2C ). This represents the joint space between the medial malleolus and the talus. In normal individuals, this distance should be 4 mm or less and should be equal to the space between the tibial plafond and the talus. Greater than 4 mm implies a lateral shift of the talus and possible ankle instability. Next is the talocrural angle, which is determined by drawing a line through the distal articular surface of the tibia and a line through the distal-most aspect of the medial and lateral malleoli ( Figure 12–2B ). This angle should be 83 degrees ± 4 degrees and is used to judge fibular length. The tibiofibular clear space may also be measured and should be less than 6 mm ( Figure 12–2D ). It represents the distance between the medial wall of the fibula and the incisural (posterolateral) surface of the tibia; a space greater than 6 mm suggests syndesmotic injury. If syndesmotic injury or malleolar injury is suspected, but not radiographically obvious, the examiner may obtain stress radiographs of the ankle after appropriate analgesia is administered. Most commonly, in the setting of a lateral malleolar fracture with concern for medial injury, the examiner stresses the ankle by dorsiflexing and externally rotating the foot, and a mortise image is obtained.
Classification
Various classification systems exist for ankle fractures. The two most commonly employed are the Weber and the Lauge-Hansen classification systems.
The Weber classification separates ankle fractures based on the location of the fibular fracture. The degree of instability is determined based on the location of the fracture. Weber A fractures describe a fracture that is distal to the syndesmosis. These are typically avulsion injuries and are usually stable. Weber B fractures occur at the level of the syndesmosis and often extend proximally, laterally, and posteriorly.
Figure 12–2. Mortise view of normal ankle showing the ( A) mortise, ( B) talocrural angle, ( C) medial
clear space, and ( D) tibiofibular clear space. (Courtesy of Timothy T. Roberts, MD)
These typically result from external rotation. Fifty percent of Weber B fractures are associated with tearing of the anterior tibiofibular ligament and are unstable in such instances. Weber C fractures occur above the level of the syndesmosis and often occur with the foot in pronation at the time of injury; they are almost always associated with a medial ankle injury, whether ligamentous or bony.
The Lauge-Hansen classification describes the mechanism of injury and can be roughly correlated with the Weber system. As mentioned, this system uses 2 variables to classify the fracture pattern: the position of the foot at the time of injury (pronation versus supination) and the direction of the deforming force (external rotation versus abduction or adduction). Four patterns are described: supinationadduction (SAd), supination-external rotation (SER), pronation-external rotation (PER), and pronation-abduction (PAb). Each pattern has a relatively consistent sequence of injury, as depicted in Figure 12–3 . Although seemingly complex, the fracture patterns follow simple rules: In supination injuries, the supinated foot has a relaxed deltoid ligament but taut lateral ligaments, thus regardless of external rotation or adduction forces, the initial injury begins laterally and progresses medially, depending on the degree of force, quality of the bone, and so forth. Conversely, the pronated foot has a tense deltoid ligament, and initial injury begins medially with either a medial malleolus fracture or a rupture of the deltoid ligament. Injuries then progress proximally and laterally to the fibula, where they become analogous to Weber C injuries. Remember that the most common pattern of injury is the SER type, which correlates typically with a Weber B pattern.
Figure 12–3. Lauge-Hansen classification of ankle fractures: 4 common sequences of injury occur
based on the position of the foot at the time of injury (supination versus pronation) and the direction
of the force applied (adduction with supination, abduction with pronation).
TREATMENT
As with any periarticular fracture, the treatment goals for ankle fractures are to restore anatomic alignment of the joint. Additional goals include restoring or maintaining fibular length and the correct rotation of the joint. After reduction of a closed fracture, cast application or splint stabilization followed by delayed casting may be definitive treatment. The success of these nonoperative treatments depends primarily on the stability of the fracture. Physical exam findings, together with radiographic analysis, determine stability. Stable ankle fractures include those presenting without widening of the mortise joint space. After reduction, minimally displaced fractures with an intact syndesmosis and mortise may be treated with immobilization and nonweightbearing in a short leg cast or splint for 4 to 6 weeks.
Open fractures or dislocations that cannot be reduced require urgent surgical treatment.
In general, patterns of injury that have widening of the syndesmosis, an increased medial clear space, or frank subluxation or dislocation of the talus should be treated initially with reduction and splinting followed, when possible, by surgical fixation. Ideally, fractures should be fixed in the acute setting before significant swelling occurs; however, if the soft tissues surrounding the ankle become too swollen, closure of the skin after internal fixation may not be possible. When significant swelling or blistering is present, fixation should be delayed until swelling subsides. This may take several days to weeks.
Complications
As with most articular injuries, a loss of range of motion is expected to some degree. Posttraumatic arthritis may result if the ankle heals with articular incongruity. Arthritis is fortunately rare, however, when the ankle heals in an anatomic position. Finally, the rate of loss of reduction in closed-treated fractures is reportedly as high as 25%. For this reason, close follow-up with serial radiographs to assess reduction and healing is essential in the subacute care of ankle fractures.
COMPREHENSION QUESTIONS
12.1 A 35-year-old man suffers a left ankle fracture after losing his balance on a fast-moving treadmill. X-rays show an oblique fracture of the medial malleolus with widening of the syndesmosis and a high spiral fibular fracture. Which category of Weber ankle fractures is most analogous to this fracture pattern?
A. Weber AB. Weber BC. Weber CD. None of the above
12.2 A 50-year-old male presents to the emergency department with right ankle pain, an inability to bear weight, and swelling over the lateral malleolus. The patient states that he twisted his ankle tripping down a flight of stairs and is complaining of “throbbing” lateral ankle pain. X-rays show a minimally displaced lateral malleolus fracture (Weber B) with a medial clear space of 3.5 mm. During your initial physical exam, palpitation of the medial malleolus also elicits tenderness. About which additional injury should you be concerned?
A. Fracture of the talar neckB. Tear of the deltoid ligamentC. Fracture of the calcaneusD. Tear of the anterior talofibular ligament
12.3 A 26-year-old athlete twists her right ankle while diving for a soccer ball during her tenure as goalie for a local travel league. She suffers a bimalleolar, minimally displaced closed ankle fracture. Her skin is soft and minimally swollen, and she is neurovascularly intact. Which of the following fracture characteristics is most predictive of a need for surgical fixation?
A. Degree of initial fibular fracture displacementB. Presence of an avulsion fracture of the medial malleolusC. Level of the fibula fractureD. Position of the talus in the ankle mortise
12.4 A 20-year-old male patient presents to the emergency department (ED) after falling off of his mountain bike. He last ate 2 hours ago, about 15 minutes before he fell. He complains of left ankle pain and has a markedly deformed ankle with exposed bone protruding through the skin. What is the single most important and immediate step in the treatment of this injury?
A. Thorough irrigation and debridement of gross contamination from the woundB. Reduce and splint the fracture in EDC. Administer intravenous antibiotics and a tetanus shot/booster when applicableD. Place nasogastric tube and proceed to the operating room for surgical stabilization
ANSWERS
12.1 C. Maisonneuve fractures, a type of pronation external rotation fracture, have a characteristic high fibular spiral fracture with a disrupted syndesmosis and tibia–fibula interosseous membrane. The medial malleolus (or deltoid ligament) is also disrupted. High fibular fractures (above the level of the syndesmosis) define Weber C fractures. Weber B fractures occur at the level of the syndesmosis, and Weber A fractures occur below it.
12.2 B. A tear or rupture of the deltoid ligament would be of concern in this patient. The question tells you that the mortise is intact (clear space of 3.5 mm) on x-ray; however, because the patient has tenderness over the medial malleolus, there must be concern for injury to the deltoid, which could result in an unstable ankle.
12.3 D. Although all of the factors here may influence the decision to surgically reduce and fix an ankle fracture, the position of the talus in the mortise is the single most important factor. Remember that widening of the ankle mortise indicates instability and is itself a surgical indication. Initial displacement is not as important as postreduction positioning.
12.4 C. Although urgent irrigation and debridement and provisional stabilization are important, administration of intravenous antibiotics within 6 hours of injury has been demonstrated to be most beneficial in reducing complications associated with open fractures.
CLINICAL PEARLS
► When examining a patient with an ankle injury, always perform a complete physical exam, including palpation of the lateral and medial malleolus, and a complete neurologic and vascular exam. ► When ordering ankle radiographs, obtain AP, mortise, and lateral views at minimum. ► On the mortise view, look for signs of instability. Remember that the medial clear space should be no wider than 4 mm and should be equal to the rest of the mortise clear space. ► Surgery is indicated in unstable ankle fractures and any open injuries. |
REFERENCES
Buchholz RW, Court-Brown CM, Heckman JD, Tornetta P, eds. Ankle fractures. In: Rockwood and Green’s Fractures in Adults . 7th ed. 2 vol. Philadelphia, PA: Lippincott Williams & Wilkins; 2010: P2147-P2179.
Egol KE, Koval KJ, Zukerman JD, eds. Injuries about the ankle . In: Handbook of Fractures . 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:76-506.
Pena F. Ankle injuries. In: Swiontkowski M, ed. Manual of Orthopaedics. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:375-379.
Sanders D. Fractures of the ankle and tibial plafond. In: Lieberman JR, ed. AAOS Comprehensive Orthopaedic Review. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2009:659-667.
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