The key to successful management of ankle fractures is distinguishing between those that are stable and those that are unstable. In the evaluation of any traumatic or twisting injury to the ankle, a fracture of the distal fibula or tibia must be considered in the differential diagnosis. Isolated nondisplaced fractures of the lateral, medial, or posterior malleolus and nondisplaced fractures of the distal fibular shaft are stable and can be managed by primary care providers. Ankle fractures in children are usually epiphyseal injuries caused by the relative weakness of the physis.
See Appendix for stepwise instructions for weight bearing and non-weight bearing short leg casts and a lower extremity splint used in the treatment of ankle fractures.
Go to Expert Consult for the electronic version of a patient instruction sheet named “Broken Foot or Ankle,” which covers the steps of care from pain relief to rehabilitation exercises. This can be copied to hand out to patients to assist them during the treatment period.
Ankle Fractures (Adult)
Most ankle fractures are malleolar fractures with the following distribution: 60% to 70% unimalleolar fractures, 15% to 20% bimalleolar fractures, and 7% to 12% trimalleolar fractures. Men and women have similar rates overall, but men have a higher rate as young adults, and women have higher rates in older age groups.
A high body mass index and cigarette smoking have been associated with ankle fractures. In contrast to other fractures common among perimenopausal and postmenopausal women, bone density does not appear to be a major risk factor.
Three bones make up the ankle joint: the distal tibia, the distal fibula, and the talus. They are bound together by a joint capsule and uniting ligaments that form a functional unit. The normal movement of the ankle mortise is dorsiflexion and plantarflexion. The perpendicular motions of inversion and eversion, which occur primarily at the subtalar joint, are the most common injuring mechanisms of the ankle joint.
There is no single widely accepted definition of the margins of the lateral malleolus. For the purpose of managing ankle fractures in primary care, the lateral malleolus refers to the distal part of the fibula that is adjacent to the talus and tibia in the tibial grove ( Figure 13-1 ). The lateral malleolus guards against excessive eversion of the ankle and foot. The most distal portion of the tibia where it articulates with the medial aspect of the talar dome constitutes the medial malleolus. The posterior aspect of the distal tibia is usually referred to as the posterior malleolus . It primarily includes the part of the tibia where the posterior tibiofibular ligament attaches.
The ligaments of the ankle include the medial deltoid ligament, three lateral ligaments (anterior talofibular, calcaneofibular, and posterior talofibular), and the distal tibiofibular ligaments ( Figure 13-2 ). The deltoid ligament, a thick triangular band with superficial and deep fibers, originates from the medial malleolus and attaches to the navicular bone, calcaneus, and talus. The posterior tibial and flexor hallucis longus tendons cross it superficially. The lateral ligaments arise on the lateral malleolus and are in close proximity to the peroneal muscle tendons. The anterior talofibular ligament provides stability during plantarflexion. The calcaneofibular ligament stabilizes both the ankle and subtalar joints, especially during inversion. The posterior talofibular ligament protects against posterior displacement of the talus but is rarely torn unless the ankle becomes dislocated. The anterior and posterior tibiofibular ligaments, the transverse ligament, and the interosseous membrane bind the tibia and fibula together just above the joint line. Together these ligaments form the ankle syndesmosis.
The posterior tibial artery and tibial nerve course together posterior and lateral to the medial malleolus. The anterior tibial artery and deep peroneal nerve run together and cross the ankle joint anteriorly, approximately in the midline.
Several features of the bones of the ankle relate to ankle biomechanics and injury patterns. The inferior surface of the distal tibia, articular and concave, is referred to as the tibial plafond or ceiling . The talus, covered largely by cartilage, is interposed between the tibia and calcaneus. The talus fits more snugly under the tibial plafond during ankle dorsiflexion. The plafond is broader anteriorly than posteriorly, which results in increased bony contact and stability in the dorsiflexed position. This anatomic relationship between the distal tibia and the talus explains why the plantarflexed ankle has the least amount of bony stability and is more vulnerable to injury in this position.
A number of classification systems exist for ankle fractures, which use the force applied and the position of the foot at the time of injury. The two most commonly used systems are the Lauge-Hansen and the Danis-Weber systems. These classification schemes are complex and do not necessarily help the primary care provider distinguish stable from unstable fractures. Rather, knowledge of the typical patterns of ankle injury and the ligamentous injuries that accompany ankle fractures helps primary care providers accurately assess the stability of the ankle joint. The bones and ligaments of the ankle essentially form a ring around the joint ( Figure 13-3 ). If the ring has only one break, the ankle joint remains stable. For a talar shift and consequent instability to develop, a ligamentous injury or fracture on both the medial and lateral sides of the ring must occur. Truly isolated malleolar fractures in the absence of injury on the opposite side of the joint are stable fractures and do not lead to abnormal joint biomechanics.
Mechanism of Injury
The forces acting on the ankle that result in a fracture are typically combination motions. Patients often cannot accurately describe the cause of injury other than reporting a twisting motion. Lateral malleolus fractures result from inversion and adduction forces that cause medial displacement. Injury to the medial malleolus generally results from eversion and abduction forces that displace the joint laterally. Eversion, abduction, vertical loading, or a combination of these forces causes fractures of the posterior lip of the tibia (posterior malleolus). Axial compression of the ankle resulting from a fall from a great height or from some other high-energy injury may produce a severely comminuted fracture of the tibial plafond called a pilon fracture .
The direction of the injuring force and the position of the foot at the time of injury determine which structures are affected and the sequence in which they are injured. An inversion force first sprains the lateral ligament complex or avulses the distal lateral malleolus ( Figure 13-4 ). If the force continues, the talus impacts the medial malleolus, causing an oblique fracture of the malleolus ( Figure 13-5 ).
On the medial side of the ankle, an eversion force first sprains the deltoid ligament or avulses the distal medial malleolus ( Figure 13-6 ). As the eversion force continues, an impaction (oblique) fracture of the lateral malleolus may occur or the syndesmosis may be ruptured ( Figure 13-7 ). External rotation combined with eversion of the ankle may result in a proximal fibula fracture, the so-called Maisonneuve fracture ( Figure 13-8 ). In this type of fracture, the medial side of the ankle is injured first followed by rupture of the anterior tibiofibular ligament, disruption of the syndesmosis, and finally a fracture through the proximal fibula.
Identifying the area of maximal tenderness, other areas of tenderness, and localized swelling can aid in determining which ankle structures are injured. The degree of swelling present during examination is not a reliable indicator of injury severity or of the presence of a fracture because swelling is probably more related to the amount of time that elapsed between injury and presentation and the patient’s actions after the injury. Although tenderness on the opposite side of the ankle may occur as a result of talar impact, an unstable ankle should be suspected when a patient has significant medial and lateral pain. Because of the possibility of associated proximal fractures, the full length of the fibula and tibia should be palpated on any patient with an acute ankle injury. Physical examination of the ankle joint to detect stability is often difficult in the acute setting because of swelling and voluntary guarding from pain and can be deferred until after radiographs are obtained. The skin and neurovascular integrity should be closely examined for signs of compromise or ischemia. Pulses of the dorsalis pedis and posterior tibialis arteries, distal capillary refill, and sensation and motor function should be assessed.
Along with detecting a fracture after ankle injury, a primary goal of ankle imaging is determining joint stability. Typically, an ankle fracture is stable if it includes all of these elements: not associated with a ligamentous injury, nondisplaced, and isolated to one malleolus.
The Ottawa Ankle Rules are well validated guidelines to aid in making decisions about the need for radiographs in a patient with an acute ankle injury ( Table 13-1 ). These standards perform well in ruling out a fracture (high sensitivity and high negative predictive value) but are poor in ruling in a fracture (low specificity and low positive predictive value). In other words, patients with negative findings based on the rules are highly unlikely to have a fractured ankle. The diagnosis for patients with positive findings based on the rules is much less certain, suggesting the need for radiography.
The standard ankle radiographic series consists of anteroposterior (AP), lateral, and mortise (AP with the foot in 15 degrees of adduction) views ( Figure 13-9 ). In reviewing ankle radiographs for signs of instability, the clinician should look for any displacement of the talus in the mortise view ( Figure 13-10 ), where the joint space between the talus and the lateral malleolus, distal tibia, and medial malleolus should be equidistant. A nondisplaced fracture of the ankle is commonly identified on only one view ( Figure 13-11 ). The lateral view must be examined carefully, especially for oblique fractures of the distal fibula and fractures of the posterior malleolus. A gravity stress mortise radiograph can be used to determine joint stability if suspicion is high and plain films are inconclusive.
In general, fractures resulting from avulsion forces are transverse, and fractures caused by talar impact against the malleoli are oblique. An oblique medial malleolus fracture after an inversion injury should raise suspicion of an associated lateral ligament sprain and a possibly unstable ankle (i.e., two breaks in the ring). An oblique fracture of the distal fibula 2 to 3 inches proximal to the ankle mortise may be associated with a medial joint injury and disruption of the tibiofibular ligaments ( Figure 13-12 ). Displaced malleolar fractures are usually accompanied by a ligamentous injury on the opposite side of the ankle.
Indications for Orthopedic Referral
Emergent Referral (Within 30 to 60 Minutes)
Open fractures and injuries associated with vascular or neurologic compromise require immediate surgical referral. Fracture dislocations must be reduce immediately to prevent complications and should be referred immediately if orthopedic consultation is readily available. See description of how to reduce an ankle dislocation at the end of this chapter.
Nonemergent Referral (Within a Few Days from Injury)
Any patient with loss of joint congruity (intraarticular fracture) or an unstable ankle or in whom the stability of the ankle joint is in doubt should be referred to an orthopedic surgeon promptly for treatment. Examples of unstable ankle injuries are fractures of both medial and lateral malleoli (bimalleolar fracture) ( Figure 13-13 ), a trimalleolar fracture (bimalleolar plus posterior malleolus fracture) ( Figure 13-14 ), or a malleolar fracture on one side with an associated ligament disruption on the opposite side. Injuries that lead to a distal fibular fracture above the tibiotalar joint line are frequently associated with a syndesmotic disruption and instability and should be referred for possible operative management ( Figure 13-15 ). Operative treatment is recommended for posterior malleolar fractures involving more than 25% of the articular surface or displaced more than 2 mm.