Introduction
The “ankle” is composed of the tibiotalar and the distal tibiofibular joints, which work in combination with the rest of the structures of the lower leg to allow standing and walking. The term “ankle fracture” is used to describe the very common malleolar fracture patterns and these are described in the first part of this chapter. Impaction injuries into the weightbearing surface of the tibial plafond are usually termed “pilon” fractures. Pilon fractures need special consideration, and are described separately in the second part of this chapter.
The importance of the tibiotalar joint is in allowing successful force transmission from the foot, via the talus, to the distal tibia during standing and walking. In order to do this the talus needs to maintain its position underneath the distal tibia and to move freely from plantar flexion to dorsiflexion. This ankle movement relies on the complex interactions between the bony structures of the distal tibia and fibula and the surrounding ligaments, tendons, muscles, and nerves. Treatment aims to restore ankle bony and soft tissue anatomy.
Pathogenesis: Etiology, Epidemiology, and Pathophysiology
The incidence of ankle fractures in the United States is 187/100 000 adults per annum1 or 4.2 per 1000 Medicare enrollees.2 The incidence of ankle fractures seems to be increasing, this is unsurprising as age and BMI are two of the most significant risk factors for fracture. History of previous ankle fracture is also a risk factor3–4. The highest incidence of ankle fractures occurs in older women aged 75 to 84 years3, 5. In contrast below the age of 50 ankle fractures are commoner in men than women.
Ankle fractures result most commonly from acute trauma, either during sport, or during a fall while running, jumping, or descending stairs or a ladder. The position of the foot during injury, as well as the direction of the force causes different fracture patterns. Understanding the anatomy of the fracture is key to understanding their pathophysiology and planning their treatment.
Anatomy and Biomechanics
Bony Anatomy
The distal tibia and distal fibula form a mortise (Figure 21.1), within which the talar dome sits. The term mortise is taken from the woodworking mortise and tenon joint, where a joint is formed between a recess (the mortise) and a corresponding projection (tenon), which mates with it. The ankle mortise is maintained by both bony and ligamentous structures.
Figure 21.1 (a) Outline of the mortise showing equal joint space. (b) Shows the tibial plafond and axis of rotation (r) of the ankle. (c) The medial clear space (m) and the syndesmotic space (s). (d) Demonstrates the marks for establishing normal fibular length.
Medial Structures: Medial Malleolus and Deltoid Ligament
The medial flare of the distal tibia forms the medial malleolus. In its normal position it helps prevent the talus from translating medially. The deltoid ligament stabilizes the medial ankle, and is composed of superficial and deep components. The superficial deltoid ligament fans out from the medial malleolus to attach to the talus, calcaneus, and navicular, and prevents eversion of the hindfoot. The thick deep deltoid ligament runs from the medial malleolus to the medial talus and is crucial in preventing abduction of the talus. Running directly posterior to the medial malleolus are the tendons of tibialis posterior, flexor digitorum longus (FDL), and flexor hallucis longus (FHL), from medial to lateral. The posterior tibial artery and nerve are described as lying between the FHL and FDL tendons. The posterior aspect of the medial malleolus usually has a groove for the posterior tibial tendon (PTT). The saphenous nerve and vein run superficially over the medial malleolus in the subcutaneous fat.
Midline Structures: Talar Dome, Plafond, and Posterior Malleolus
The tibial plafond sits at approximately 87° to the mechanical axis of the tibia. It is covered with articular cartilage and articulates directly with the talar dome. It has a small sagittal ridge dividing it into a wider lateral and smaller medial part.
The talar dome closely matches the curvature of the distal tibial plafond. It is bi-lobed with the sagittal prominence of the tibial plafond sitting within the groove. This fit is crucial as studies have shown that translating the talus 1 mm may increase joint pressures by as much as 40%6–7, predisposing the ankle to post-traumatic arthritis. The slightly larger radius of the lateral portion of the talar dome results in dorsiflexion causing the foot to externally rotate slightly. Additionally the talar dome is wider anteriorly than it is posteriorly, thus the talus has a more stable fit within the mortise when the ankle is dorsiflexed. The distal fibula accommodates the differential width, by rotating slightly as the talus dorsiflexes, and the wider portion moves into the mortise.
The posterior malleolus is part of the weightbearing articular surface and injury to it does affect ankle joint function. It has also been postulated that the posterior malleolus helps to prevent posterior translation of the talus8, although there is contradictory evidence on this. Early research in cadavers demonstrated that resection of up to 40% of the posterior malleolus, leaving the lateral structures intact, resulted in little to no translation with posteriorly directed forces9–10. On the other hand, it has been shown in cadavers that with an axially directed force and resection of 25% of the plafond there is increased posterior talar translation11.
The posterior malleolus is also the attachment point for the posterior inferior talofibular ligament (PITFL). With combined fractures of the posterior malleolus and the fibula the PITFL often remains intact. As a result reduction of the fibula and posterior malleolus is linked. The regions of the tibia that attach to the PITFL and the anterior inferior tibiofibular ligament (AITFL) posteriorly are eponymously named, with the PITFL being attached to the Volkmann fragment (posterolateral) and AITFL to the Chaput fragment (anterolateral).
Lateral Structures: Lateral Malleolus and Syndesmosis
The distal fibula articulates with the distal tibia as well as the lateral aspect of the talus. It sits slightly posteriorly in the crescent-shaped incisura of the distal tibia. The fibula rotates slightly in ankle dorsiflexion to accommodate the wider anterior aspect of the talar dome. The syndesmotic ligaments hold the fibula in place. There are four main ligaments, which help to maintain this relationship – the interosseous membrane (IOM), AITFL, PITFL and the inferior transverse ligament (ITL) (Figure 21.2). These ligaments help resist external rotation of the fibula by the talus and with the deltoid ligament also resist lateral translation.
Figure 21.2 Ligaments of the ankle. (a) Anterior ankle. (b) Axial view showing components of the syndesmosis. (c) Lateral ankle ligaments. (d) Medial ankle ligaments.
The more superficial ligaments are also important in maintaining ankle function. The anterior talofibular ligament (ATFL) runs from the distal fibula to the talar neck. It helps prevent anterior translation of the ankle in slight plantar flexion and is the most commonly injured ligament in ankle sprains. The calcaneofibular ligament (CFL) runs from the distal tibia to the calcaneus, deep to the peroneal tendons. It primarily resists ankle inversion.
Just posterior to the lateral malleolus run the peroneal tendons in their tendon sheath. They are kept in place by the strong peroneal retinaculum. The superficial peroneal nerve pierces the peroneal fascia approximately 10 to 12 cm from the distal tip of the lateral malleolus and then courses superficially and anteriorly to cross the tibiotalar joint in front of the fibula, adjacent to the peroneus tertius – the nerve is at risk in lateral approaches to the fibula.
Presentation
History
Patients usually present with a history of trauma, although neuropathic patients may present simply with swelling or deformity. It should not to be forgotten that neuropathic patients also present with pain.
The history should include the time of injury and the nature of the trauma, including if possible the exact mechanism and position of the foot. It is important to specify the location of pain both in the foot and ankle, as well as generally.
It is particularly important to record comorbidities such as peripheral vascular disease and diabetes12–14. Lifestyle factors including smoking, occupation, and recreational activities should also be noted.
Physical Examination
The physical examination in all trauma patients should start with the “ABC” of airway, breathing, and circulation, with systemic stabilization if necessary. Local examination of the foot and ankle should be prompt and can often be undertaken as the patient is being stabilized. In particular signs of vascular or skin compromise as well as gross deformity should be noted. Swelling, evidence of previous trauma, and surgical scars should be recorded. The bony prominences of the foot and ankle are palpated, including the medial and lateral malleoli, the base of the fifth metatarsal, navicular tuberosity, calcaneus, and proximal fibula.
Vascular examination is important in all cases. Vascular injuries acutely require urgent treatment, whereas, chronically, peripheral vascular disease will impact upon surgical treatment. The vascular examination should include palpating both the dorsalis pedis and posterior tibial pulses and noting capillary refill. If the pulses are not palpable, Doppler ultrasound should be used to record their presence.
Neurological examination should include testing skin sensation in the distribution of the superficial peroneal, deep peroneal, saphenous, sural, and tibial nerves. Additionally great toe dorsiflexion (deep peroneal) and plantar flexion (tibial nerve) should be assessed15. There is debate about the management of nerve injuries, with some advocating urgent repair and others recommending observation, even if the nerve injury is complete16–17. Damage to the tibial nerve is an important factor in determining limb viability, nevertheless good results are seen with tibial nerve injury18, thus absence of the tibial nerve is not, in itself, an indication for amputation.
Compartment Syndrome
Compartment syndrome of the leg or foot can complicate ankle trauma, although it is commoner after tibial shaft fracture. Compartment syndrome should always be considered in patients who have pain disproportionate to their injury, or neurological abnormality. If there is any clinical suspicion of a compartment syndrome then compartment pressures should be measured.
Imaging
The indications for radiographs in ankle trauma have been widely studied to try and eliminate unnecessary radiographs. The Ottawa ankle rules advocate obtaining radiographs for anyone who has tenderness who cannot bear weight, has medial tenderness over the posterior edge of the medial malleolus or navicular, or lateral tenderness over the posterior edge of the fibula and base of the fifth metatarsal. Special care should be taken in intoxicated or obtunded patients, those with peripheral neuropathy, or with swelling that prevents direct palpation of bony prominences.
Radiographs
Standard imaging includes three views of the ankle. Some authors have looked at limiting the study to two views, a lateral and mortise, but this approach has been shown to miss as many as 18% of fractures19. Physical examination for tenderness should help guide further imaging of the tibia, knee, and foot. Additionally, any patient whose ankle radiographs show evidence of a syndesmosis injury, without a fibular fracture, should have full-length tibial and fibular films, to exclude a proximal fibula fracture.
The fracture pattern, integrity of the ligamentous structures, and the weightbearing surfaces should be noted on the radiographs. Normal radiographic relationships are shown in Figure 21.1. In general the mortise view should show equal ankle joint space laterally, superiorly, and medially.
As radiographs for trauma are usually not obtained weight bearing, they may fail to show ligament injury. This most commonly occurs in Weber B, supination external rotation type II fractures where it is unclear whether the deltoid ligament is disrupted, or not. In those patients stress imaging may be helpful20. The timing and technique remains controversial. Some have advocated gravity stress views, where the patient’s foot is placed with the lateral malleolus toward the ground and a mortise radiograph is taken21–22. A manual stress test where the physician forcibly dorsiflexes and externally rotates the hindfoot while obtaining a mortise radiograph has also been described23. Still others have advocated weightbearing radiographs as a true measure of physiologic stress. The timing of these radiographs (emergency room vs. first clinic visit) is up to the surgeon, and to some degree the ability of the patient to tolerate them.
Advanced Imaging
Complex imaging such as CT or MRI scans is generally not required for the evaluation of malleolar fractures. CT scans are helpful if there is concern about impaction of the tibial plafond, the morphology of a fracture extending into the plafond is unclear, or if there is uncertainty as to the fracture configuration. MRI scanning can be helpful in the evaluation of soft tissue structures, but is rarely indicated in the setting of an acute ankle fracture, as the soft tissue edema makes interpretation difficult, and clinical decision making is not helped.
Classification
Lauge–Hansen Classification
This classification scheme (Figure 21.3) was developed as a result of cadaver research. The foot was placed into a specified position and a force applied. The resulting fracture patterns were divided into two part descriptive names, with the first part being the position of the foot (supination or pronation) and the second the direction of the force (external rotation, abduction, or adduction). Increasing severity was designated by numbers. This combination creates characteristic fracture patterns of the malleoli.
Figure 21.3 Lauge–Hansen classification of ankle fractures. (a) Supination adduction; (b) supination external rotation; (c) pronation abduction; (d) pronation external rotation.
Supination adduction. The lateral structures fail first (fibula or calcaneofibular ligament) and the talus is then driven up into the talar dome.
Fibular fracture pattern: transverse, usually below the tibiotalar joint
Medial malleolar pattern: vertical, often with impaction of the medial plafond.
Supination external rotation. This is the commonest pattern following a twisting injury where the failure line moves rotationally around the ankle, starting laterally and moving posteriorly to the medial side. The structures are injured in the following order:
1. anterior talofibular ligament
2. lateral malleolus
3. posterior inferior tibiofibular ligament or posterior malleolus
4. deltoid ligament or medial malleolus.
The fibular fracture pattern is short oblique at the level of the tibiotalar joint. The medial malleolus is an oblique avulsion at the shoulder of the plafond.
Pronation abduction. This fracture pattern starts medially with disruption of either the deltoid or medial malleolus. It then moves laterally through the syndesmosis and eventually the fibula fracture with a bending motion.
Fibular fracture pattern: transverse, comminuted fracture at the level of the joint
Medial malleolar fracture pattern: transverse avulsion fracture, often distal to the plafond.
Pronation external rotation. A twisting mechanism, which starts medially with disruption of the medial malleolus or deltoid ligament, and then extends through the syndesmosis eventually leading to fibular fracture.
Fibular fracture pattern: a short spiral oblique fracture proximal to tibial plafond
Medial malleolar fracture pattern: transverse avulsion fracture, often distal to the plafond.
Weber/AO Classification
The Weber classification system (Figure 21.4) is broken down into three different fracture types based solely on the location of the fibular fracture.
A: Distal to the plafond
B: At the level of the plafond
C: Proximal to the plafond.
The AO classification (Figure 21.5) is based upon the Weber classification, but adds subclassifications to account for additional injuries to the medial and posterior malleoli.
Figure 21.4 Weber ankle fracture classification. The fibular fracture is designated A, B, or C, according to the level of the fracture.
Figure 21.5 AO classification of ankle fractures.
Treatment
The overall aim in treating ankle fractures is to restore a stable, congruent ankle joint. This anatomy is restored, while the soft tissue injury is minimized.
Initial Treatment
Initial treatment includes reduction and temporary stabilization. Reduction decompresses the soft tissues and provisionally restores alignment. This can usually be achieved closed. Even if future surgical intervention is planned, a poor reduction should not be tolerated. If proper reduction cannot be obtained in the emergency room or clinic then the patient should promptly be taken to the operating room for an open reduction. After reduction, the patient should be placed in a well-molded and padded splint to hold the reduction. Post-reduction films should be obtained to confirm the position.
Bosworth fractures are rare fractures where the proximal aspect of the distal fibula is trapped posterior to the distal tibia (Figure 21.6). They need to be recognized as closed reduction will not be possible, and may even cause further harm. Bosworth fractures should be treated with early open reduction and internal fixation.
Figure 21.6 Bosworth fracture. Note the position of the fibula behind the distal tibia, this makes closed reduction very difficult.
Vascular Compromise
If signs of vascular compromise are present the ankle should be promptly reduced in the emergency department. If this does not restore blood supply to the foot, or if a vascular injury is readily apparent, for example with visible pulsatile bleeding, a vascular opinion should be obtained immediately. If vascular repair is necessary a temporary external fixator is applied before undertaking the vascular repair, in order to restore stability and protect the repair. External fixation is usually advocated, as it is generally faster to apply and minimizes the ischemic time. External can then be revised to internal fixation, once the vascular supply has been stabilized.
Open Fractures
Patients with open ankle fractures should receive immediate intravenous antibiotics in the emergency department followed by timely surgical debridement in the operating room. The recommended antibiotics in our institution are:
all open fractures: second-generation cephalosporin
larger (>10 cm) or grossly contaminated wounds: second-generation cephalosporin and an aminoglycoside
farmyard wounds: second-generation cephalosporin and penicillin.
Historically, a six- to eight-hour window post-injury for surgical debridement has been regarded as the gold standard. Recent data has called this into question, showing equivalent results with debridement at up to 24 hrs24. This study also demonstrated that early admission to a definitive trauma center appears to have a significant benefit in reducing the rate of infection. It is possible that early resuscitation and antibiotic administration may play a role in this24.
Whenever possible, definitive surgical fixation of the fracture should be undertaken at the time of the surgical debridement. However, it is important that the overlying skin can be closed without tension over the hardware. This is often possible for small, simple wounds, but if there is a large wound that cannot be closed, then the fracture site should be thoroughly debrided and external fixation applied. The external fixation needs to be placed well away from the zone of injury and clear of possible future incisions. The external can then be changed to internal fixation at the time of definitive soft tissue coverage, if the soft tissues allow.
If additional soft tissue coverage is needed, such as a local or free flap, this should only be undertaken once all necrotic tissue has been debrided. This debridement may require multiple trips to the operating room, to allow proper assessment of soft tissues. Nevertheless, coverage should be undertaken as early as possible, although the timing of definitive soft tissue coverage has not been shown to be a factor in the later development of infection24.
Definitive Treatment
The goal is to obtain a stable, congruent joint with normal movement. This is achieved with anatomic reduction, stable fixation, and the early institution of joint range of motion25.The key is to anatomically reduce the talus and restore the components of the mortise to maintain that position.
The components include:
– restoration of fibular length and rotation
– reduction of the syndesmosis
– reduction of the medial malleolus
– reduction of the posterior malleolus
– reduction of any step off, gapping, or impaction of the tibial plafond.
If these components can be achieved by non-operative means then no surgical intervention is needed. If they cannot, then surgical treatment should be considered. As with all surgical treatment the benefits should outweigh the risks. Factors such as age, medical comorbidities, especially peripheral vascular disease and diabetes, occupation, cigarette smoking, recreational activities, and ability to comply with postoperative protocols need to be considered and discussed with the patient before finally confirming the treatment plan.
Specific Considerations for Operative Treatment
Weber A
Distal fractures of the fibula are the result of supination/adduction tension forces. The fractures are often very distal and fixation can only be achieved using either a tension band wire, or a tension band plate and screws.
Any associated medial malleolar fracture is the result of impaction of the talus through the shoulder of the tibial plafond. The medial tibial joint surface is also often impacted as well, and this needs disimpaction before fixation. The fracture is opened and the subchondral bone is elevated. The resultant bone defect is filled with autograft or allograft. The medial malleolar fracture is usually vertical and should be fixed either with horizontal lag screws or a buttress plate and lag screws. Remember that the lag screws should be placed perpendicular to the fracture line. It is important to check that the screws do not penetrate the joint.
Weber B
In treating Weber B fibular fractures the emphasis is on the restoration of fibular length and rotation (Figure 21.7). There is often a long oblique fracture pattern, which lends itself to lag screw fixation with either one or two screws. A lateral or posterolateral neutralization plate is then used to stabilize the construct. If there is fibular comminution, then a bridging plate should be used. The medial malleolar fracture is also fixed.
