Ankle Fracture.

For many primary care physicians, ankle injuries are the most common sports-related injury seen in their practice. Of those patients evaluated for ankle injuries, only approximately 15% have a clinically significant fracture. Therefore, familiarity with a thorough ligamentous examination and the Ottawa ankle rules is essential for proper management.

Successful primary care management of an ankle fracture begins with differentiation of a stable injury versus an unstable injury. The bones and ligaments of the ankle form a ring around the ankle mortise; thus, for instability to occur, ligamentous injury or fracture must include both the medial and lateral sides of the ring. The ring involves the structures that surround the talus, which are composed of the tibial plafond, the medial and lateral malleoli, the deltoid ligaments, the calcaneus, and the intraosseous membrane.

Generally, isolated nondisplaced distal fibular or distal tibial fractures are stable when no ligamentous instability is present on the opposite side of the ring. Careful evaluation of the ankle for medial and lateral swelling and ecchymosis should be routine, and their presence should increase clinical consideration of an unstable injury.

The distal tibia, distal fibula, and talus bones make up the ankle joint. These 3 bones are bound together by the joint capsule and surrounding ligaments. The anatomic relationship of the tibial plafond (joint surface of the distal tibia) to the talus is important for ankle stability. Because the anterior portion of the talus is more broadly shaped, dorsiflexion increases bone surface contact, thus improving stability. This relationship causes decreased stability during plantarflexion, accounting for the vulnerability to ligamentous injuries when the foot is plantarflexed.

Forces acting on the ankle lead to typical fracture or ligamentous patterns. Determining the position of the ankle during injury can assist in assessing for ligament stability. Although simple unidirectional forces can be involved in an ankle injury, multidirectional forces are usually involved, making diagnosis a challenge.

Medial complex injuries typically occur from eversion and abduction forces. The medial complex consists of the medial malleolus, the medial facet of the talus, and the superficial and deep components of the deltoid ligament. Eversion of the ankle causes injury to the superficial deltoid ligaments and, if sufficient, the deep deltoid ligament. Avulsion of the distal medial malleolus tends to occur in young and old patients because the ligamentous strength may be greater than the strength of the bone in these individuals. With continuation of these forces, impaction of the distal lateral malleolus occurs, resulting either in rupture of the syndesmosis or in transverse fracture of the distal fibula.

Most unstable ankle fractures are the result of excessive external rotation of the talus with respect to the tibia. If the foot is supinated at the time of external rotation, an oblique fracture of the fibula ensues. If the foot is pronated at the time of external rotation, a mid- or high-fibular fracture results.

The lateral complex consists of the distal fibula, the lateral facet of the talus, and the lateral collateral ligaments of the ankle and subtalar joints. Lateral malleolus injury (most common type of fracture involving the ankle) typically occurs with supination–external rotation forces. The inversion force first strains the lateral ligament complex or avulses (transverse fracture) the lateral malleolus. With continuation of this force, the talus impacts the medial malleolus, causing an oblique fracture of the distal tibia. Inversion ligamentous injuries of the ankle are the most commonly observed soft tissue trauma in sports.

Posterior malleolus injury typically occurs with a supination-external rotation or a pronation-external rotation injury and represents avulsion of the posterior tibiofibular ligament from the posterior distal tibia.

History: The following important questions should be included in the history of the patient's present illness:

What was the mechanism of the injury? Was it inversion or eversion? Many patients cannot recall whether their foot was plantarflexed or dorsiflexed; if the patient does know the position, this information is useful in assessing stability.

Was the patient able to bear weight after the injury? The Ottawa ankle rules specify that the inability to bear weight immediately after the injury or at the time of the radiograph is taken indicates the need for radiographic examination because of the increased risk of a clinically significant fracture.

Is there or was there an audible sound (eg, a pop)?

Is there a history of previous trauma to the ankle?

Physical: Begin the physical examination of the ankle by inspecting for swelling and ecchymosis and by palpating for areas of maximal tenderness. However, swelling is time-dependent and may be an unreliable indicator of the presence or the severity of the injury. Generally, more severe injuries are accompanied by more severe swelling.

Assess the range of motion in plantar flexion, dorsiflexion, inversion, and eversion.

Assess strength in all of the same motions.
Assess ligamentous laxity with talar tilt and drawer testing.
Assess and document the neurovascular status.
Begin palpation of the medial and lateral malleoli at the distal posterior margins because the incidence of a false-positive result is increased when palpating the anterior portions.

The Ottawa ankle rules specify that if a patient demonstrates tenderness at the posterior malleoli (up to and including the crest), then the likelihood of a fracture is increased and radiography should be performed.

Failure to palpate the entire distal 6 cm of both malleoli is a common error made by physicians. Failure to do so increases the likelihood of missing a clinically significant fracture.

Palpate over the tibial and fibular physis in children. If tender, assume the patient has a type I Salter-Harris classification of epiphysial plate injury, even if radiographic findings are negative.
Crepitation felt during palpation of the ankle is suggestive of underlying fracture pathology and necessitates radiologic examination.

Check the joint above and below the area of the patient's chief complaint in order to not miss concomitant adjacent fractures.

Palpate over the proximal fifth metatarsal and navicular for tenderness.

Palpate the soft tissues, including ligamentous areas, peroneal and posterior tibial tendons, and the anterior process of calcaneus, to assess injury to these areas.

Palpate for tenderness over the proximal fibula to exclude potential Maisonneuve fracture (proximal fibular fracture associated with medial-sided and syndesmotic injury).

The Danis-Weber classification for ankle fractures is simple and is the most useful for primary care management. This classification scheme is based on the level of the fracture in relationship to the joint mortise of the distal fibula.

Type A fractures are horizontal avulsion fractures found below the mortise. They are stable and amenable to treatment with closed reduction and casting unless accompanied by a displaced medial malleolus fracture.

Type B fracture is a spiral fibular fracture that starts at the level of the mortise. This type of fracture occurs secondary to external rotational forces. These fractures may be stable or unstable depending on ligamentous injury or associated fractures on the medial side.

Type C fracture is above the level of the mortise and disrupts the ligamentous attachment between the fibula and the tibia distal to the fracture. These fractures are unstable and require open reduction and internal fixation.

No routine laboratory studies are indicated unless syncope or other medical conditions are involved.

Radiographs should include anteroposterior, lateral, and mortise views (which are taken with the foot internally rotated 15-20°). Stress-view radiographs have a limited role in evaluating an acute ankle injury. They should only be taken while a patient is under anesthesia prior to reconstructive surgery. A standing mortise view of the ankle can help identify ligamentous instability in patients who are difficult to examine. Comparison of the normal radiographic relationships from the mortise and standing mortise views shows loss of the normal tibiofibular overlap and asymmetry of clear spaces. A comparison view with the uninjured ankle can be useful in difficult cases.

When reviewing ankle radiographs, consider that transverse fractures usually result from avulsion forces, whereas oblique fractures (usually fibular) generally result from torsional stress of the talus against the malleolus. Vertical malleolar fractures are secondary to an impact on the talus. Any displaced malleolar fracture should be considered unstable, and they are almost always associated with ligamentous injury of the opposite side. In general, all displaced medial malleolus fractures and oblique fibular fractures that are 2- 3 inches proximal to the joint line should be assumed to have associated ligament injury and should be considered unstable.

In addition to using the radiographic guidelines of alignment, bone, and connective tissue to evaluate ankle radiographs, checking for the 5 most commonly missed foot and ankle fractures is advised. Close attention to the fifth metatarsal base, lateral process of the talus, os trigonum or posterior malleolus, anterior process of the calcaneus, and talar dome (forming the mnemonic FLOAT) can help correlate radiographic findings with tenderness upon physical examination.

The radiographic relationships of the ankle mortise view are as follows:

A lateral clear space of more than 2 mm suggests a syndesmosis sprain.

The normal tibiofibular overlap is greater than 1 mm .

The normal medial clear space is less than 4 mm or a difference from medial to lateral of less than 2 mm .

Radiographic relationships of the anteroposterior ankle view are as follows:

A medial clear space of more than 3 mm may indicate deltoid ligament or syndesmosis injury.

The tibiofibular space is normally less than 6 mm .

In the standing anteroposterior view, syndesmotic widening of greater than 3 mm indicates syndesmotic sprain.

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