Bony Anatomy

The hindfoot consists of the talus and the calcaneus. The talus acts as a passive, intercalated segment between the leg, the calcaneus, and the midfoot. Together they create a mobile unit that provides stability in all phases of gait, transmits the forces for propulsion, allows the foot to adapt to variable ground surfaces, and supplies proprioceptive feedback regarding foot position.

The bones of the midfoot are the navicular, cuboid, and the three cuneiforms. The midtarsal joint, which is also known as Chopart’s joint, comprises the calcaneocuboid and the talonavicular joints, with the latter contributing the majority of midfoot motion. The midfoot is unlocked and permits significant accommodative foot motion through the midtarsal joint in stance phase, but it locks and forms a stable locked lever in the propulsive phase of the gait cycle. Preservation of midfoot function by accurate anatomical reconstruction after injury leads to better functional outcomes. As the midtarsal joint is a functional entity any navicular or cuboid fracture cannot be considered in isolation. The principles for treating talus fractures are outlined in Table 22.2.

It is helpful to consider the foot as two functional columns: a medial column including the talus, navicular, and the three cuneiform bones with the three medial metatarsals, and a lateral column, which includes the calcaneus, cuboid, and the lateral two metatarsals (Figure 22.2). The medial column provides a stable arch, which transmits the forces of propulsion, while the lateral column acts as a shock absorber permitting adaptation of foot position to the terrain.

Figure 22.2 (a) The lateral and (b) the medial columns of the foot.

The relative lengths of the two columns vary with foot morphology. A planovalgus foot results from relative lengthening of the medial column, or shortening of the lateral column. The converse can be considered to be true in a cavovarus foot. In a traumatized foot a column may be acutely shortened – if this is left untreated, the foot will be deformed. Thus in the traumatized foot careful analysis of the CT scans and consideration of column length is important in reconstruction. In principle, each column should have its length and alignment re-established, to restore the hindfoot–forefoot relationship. This may necessitate bridge fixation across mobile joints such as the talonavicular, calcaneocuboid, and the fourth and fifth TMTJs. This can be achieved with internal, external, or a combination of both fixation methods. Any joints that are spanned need to be mobilized as soon as the fractures have healed by removing the spanning fixation.

In the authors’ experience, primary arthrodeses are technically challenging in the acute setting. Cases to be considered for primary arthrodesis are often the highest energy injuries with most comminution, such that compression across these crushed joints risks shortening the column. Thus the authors prefer to restore the foot shape and perform secondary arthrodeses, as salvage procedures.

Vascular Anatomy

The arterial supply to the foot is through the posterior tibial, dorsalis pedis, and peroneal arteries. There is a generous blood supply to the long bones of the foot and those tarsal bones providing tendon origins or insertions. However, the talus and the navicular have tenuous blood supplies, which has implications for surgical treatment and the outcome of injury.

Sixty percent of the surface of the talus is covered in articular cartilage. The remaining 40% is occupied by joint capsular reflections and ligament insertions. There are no tendon origins or insertions. The vascular supply to the talus comes from anastomoses between the anterior and posterior tibial arteries and the peroneal artery¹. The talar body is supplied from the anastomoses inferiorly in the tarsal canal, superiorly from the dorsalis pedis artery, and medially through branches within the deep deltoid ligament. In talar neck fractures the vascularity of the talus can be damaged, not only from the injury itself, but also from the surgical approach used to treat the injury. Magnetic resonance angiography has quantified the relative contributions of the major vessels to the talus as 47% from the posterior tibial artery, 36% from the anterior tibial artery, and 17% from the peroneal artery².

The vascular supply to the navicular is also from both the dorsalis pedis and the posterior tibial arteries, as well as an indirect supply through the tendon attachment of the tibialis posterior onto the tubercle. The arterial supply is radial in nature leaving the central area of the navicular prone to avascular change. The blood supply to the cuboid and cuneiforms is less tenuous and infarction of these bones following trauma is uncommon.

Lastly, the microvascular supply to the soft tissue envelope of the posterior and lateral aspects of the hindfoot needs to be appreciated. Terminal branches of the posterior peroneal artery supply the angiosomes of the skin flap raised in an extended lateral approach to the hindfoot to afford access to the calcaneus in open fracture fixation³.

Extra-Articular Fractures of the Calcaneus

Excluding open injuries as a consequence of a direct blow to the heel, any activity that results in a strong contraction of the gastrocnemius–soleus complex can result in an avulsion fracture at its insertion on the calcaneus. This is particularly true in osteopenic bone and in neuropathic patients, who are usually diabetic. With the lack of significant soft tissue cover, the single most important consideration is whether the skin overlying an avulsion fracture is compromised (Figure 22.3). Skin compromise occurs in 20% of these fractures⁴. Any threatened skin requires urgent treatment in the form of fracture reduction and fixation to reduce the risk of soft tissue loss and the requirement for free tissue transfers and even trans-tibial amputation⁴. The authors’ preferred method of fixation is through a lateral approach and to apply a locked plate across the fracture, as attempts to use lag screw fixation require surgical incisions close to the compromised soft tissue envelope. In those fractures with minimal displacement and no soft tissue compromise, management in a walking cast may be possible. It is rare to have to fix these fractures in the diabetic patient.

Figure 22.3 Closed tongue-type extra-articular fracture of the calcaneus with threatened overlying skin. It was treated with emergency open reduction and locked plate fixation through a lateral approach.

Fractures of the Anterior Process of the Calcaneus

Broadly, these fractures fall into two distinct groups and account for 15% of all calcaneal fractures⁵. Firstly, the anterior process of the calcaneus is prone to injury as part of a high-energy disruption of the midtarsal joint, and the cuboid compresses the anterior process⁶. In these cases, the principles of restoration of the lateral column of the foot need to be applied. This is discussed later in the chapter.

Secondly, and more commonly, fractures of the anterior process are avulsion injuries induced by the midfoot being forced into an adducted and plantar flexed position. In this injury tension across the bifurcate ligament avulses the anterior process.

A high index of suspicion is required for these injuries with careful palpation over the sinus tarsi and lateral to the extensor digitorum brevis muscle belly, and scrutiny of plain radiographs. Often the oblique and lateral views are the most helpful, but if doubt persists a CT scan is indicated. Anterior process fractures are frequently misdiagnosed as ankle sprains⁵.

In small, minimally displaced fracture fragments, a compressive bandage or a weightbearing cast or boot will allow symptoms to settle. Up to 25% of patients take a year to become pain free⁷. In some symptomatic cases with larger fracture fragments and in the event of progression to symptomatic non-union, surgery to excise the fragment may be necessary⁷. Outcomes in those fractures that are missed or go on to non-union are often poor with persistent pain irrespective of the late treatment instituted.

Intra-Articular Fractures of the Body of the Calcaneus

Seventy-five percent of calcaneal fractures are intra-articular, with 90% resulting from a fall from a height⁸. The majority of injuries occur in males between the ages of 30 and 60 years. Ten percent of calcaneal fractures are associated with spinal column injuries and a similar figure are bilateral. The dense talus acts as a hammer to the posterior facet of the subtalar joint, creating a primary fracture line that splits the calcaneus into an anteromedial fragment containing the sustentaculum tali and a posterolateral fragment incorporating the lateral portion of the posterior facet. Essex-Lopresti described a secondary fracture line. This could be of two types, a joint depression or a tongue type⁹. The joint depression splits the posterior facet of the subtalar joint into two, creating joint incongruity. Radiologically this leads to a flattened Bohler’s angle. Bohler’s angle is the angle formed by the intersection of a line drawn from the tip of the anterior process to the posterior aspect of the posterior facet with the line from the latter to the tip of the posterior tubercle. This angle normally measures 20 to 40°. When Bohler’s angle is flattened this implies that there is posterior facet depression and loss of calcaneal height. This angle is important, as a reduced Bohler’s angle is associated with a poor outcome¹⁰. Almost two-thirds of fractures extend into the calcaneocuboid joint.

The overall effect of significant calcaneal injury is usually loss of calcaneal height and an increase in calcaneal width. This can lead to impingement between the lateral calcaneal wall and the tip of the fibula, with the peroneal tendons painfully trapped between the two. The enveloping soft tissues around the calcaneus are also injured. Open fractures are not uncommon and plantar wounds, in particular, have a worse prognosis than medial or lateral wounds. Injury to the heel fat pad can lead to chronic pain.

Several classification systems have been suggested to aid in the management of these fractures. No single classification has achieved universal acceptance^{9, 11–12}. Although it does not include the calcaneocuboid joint, the most familiar classification was described by Sanders¹² and uses axial CT views of the posterior facet to assess the number of longitudinal fracture lines of the posterior facet of the subtalar joint, grading them in increasing severity from type 1 to 4:

• 
  

  Type 1 is undisplaced (<2 mm)

  
  
• 
  

  Type 2 has one intra-articular fracture line

  
  
• 
  

  Type 3 has two intra-articular fracture lines

  
  
• 
  

  Type 4 has three or more intra-articular fracture lines.

The position of the fracture lines (Figure 22.4) is used to note the position of the fracture line on the posterior facet (for example 2b, or 3ab).

Figure 22.4 (a) Axial CT scans of both calcanei. On the left foot, the scans show a Sanders 3bc fracture of the posterior facet. Note the fracture of the inferomedial aspect of the right posterior tubercle. (b) Line diagram of the axial cut through the posterior facet demonstrating the fracture line configuration for the Sanders classification¹².

The treatment of intra-articular calcaneal fractures can be non-surgical, with analgesia, splintage, and physiotherapy, or surgical, with open reduction and internal fixation (Figure 22.5). Factors governing the outcomes following these injuries can be divided into patient related, fracture related, and surgeon related. Patients who smoke, are over the age of 50, have significant comorbidities, who are manual workers, or are involved with litigation seem to have a poorer outcome¹⁰. Fracture-related issues associated with a poorer outcome are those associated with the energy of the injury namely: open fractures, bilateral fractures, polytrauma, a Bohler’s angle of less than 0° and Sanders type 4 fractures. Intuitively, the quality of articular reduction should correlate with the surgical outcome.

Figure 22.5 (a) Lateral radiograph showing an intra-articular fracture of the calcaneus with depression of the posterior facet. (b) Lateral and (c) axial radiographs of the calcaneus following open reduction and internal fixation.

There remains clinical uncertainty as to the optimal management for adults with a displaced intra-articular calcaneal fracture, as there is insufficient high-quality evidence to establish whether operative or non-operative treatment is better. Two large randomized controlled trials comparing surgical and non-surgical treatment have been reported. In Canada, a trial showed no conclusive proof that open reduction and internal fixation achieved better results than non-operative treatment¹⁰. Further subgroup analysis suggested that the results of operative treatment were marginally better in young women, non-manual employees, non-smokers, and those who were not pursuing compensation. With the numerous confounding variables that apply to these fractures, a pragmatic prospective randomized controlled study was required. This led to the inception and completion of the UK Heel Fracture Trial. The results from this study show that after excluding those fractures “with gross deformity,” the remaining cases with more than 2 mm displacement of the posterior facet, treated with an extended lateral approach, demonstrate no improvement in outcome when comparing internal fixation with non-operative treatment¹³. Of course this does not take into account that it is easier to perform a subtalar fusion for post-traumatic arthrosis of the posterior facet in a reconstructed calcaneum, as opposed to a severely malunited one.

The rationale for surgical treatment of Sanders type 2 and 3 fractures has been directed at open fractures, those with subfibular impingement, and those cases where a malunion would lead to a dorsiflexed talus and subsequent restricted ankle dorsiflexion (Figure 22.6). Other criteria for fixation include greater than 3 mm displacement of the posterior facet or varus malalignment of the posterior tubercle. In may ways the most important factor is Sanders group’s demonstration that a subtalar fusion following initial open reduction and internal fixation (ORIF) of a calcaneal fracture has a better outcome than subtalar arthrodesis of a malunited fracture, which was not reduced acutely¹⁴. Open reduction and internal fixation is best performed through an extended lateral approach, once the soft tissue envelope shows signs of wrinkling. Reconstruction of the calcaneus aims to reduce the posterior facet of the subtalar joint, the calcaneocuboid joint, Bohler’s angle, and any varus or valgus malalignment. With wound complications being a concern, minimally invasive techniques have been tried with some low-grade evidence that they are an effective alternative in less severe, Sanders type 2 fractures^15–16.

Figure 22.6 (a) CT image of a malunion of an intra-articular fracture of the calcaneus demonstrating a dorsiflexion deformity of the talus leading to restricted ankle dorsiflexion. (b) Note the subfibular impingment of the lateral calcaneal wall. (c) Lateral plain radiograph of a malunion of the calcaneus showing the loss of heel height.

Low-Energy Fractures of the Talus

Avulsion Fractures

In minor inversion or eversion injuries of the ankle, the talus is prone to injury¹⁸. Although excluded from the Ottawa rules¹⁹, avulsion fractures from the neck of the talus occur (Figure 22.7a). These injuries occasionally need immobilization and physiotherapy, but usually recover completely. It should be noted that an avulsion of this sort may be the radiographic marker of a midtarsal dislocation. In midtarsal injuries there will be more swelling and there may also be bony avulsions from the lateral column.

Figure 22.7 (a) Lateral plain radiograph demonstrating avulsion of the capsule from the neck of the talus following an ankle inversion injury. (b) Plain radiograph and (c) CT of an acute osteochondral fracture of the lateral talar dome. The fracture fragment has inverted. (d) Six months post open reduction and internal fixation of the fracture with bioabsorbable pins.

Monitoring Post-Injury Progress and Hawkins Sign

In 1970, Hawkins observed a subchondral radiolucent band within the talar dome on plain radiographs²⁴. It is best appreciated on the AP radiograph, but can also be detected on the lateral. If present, this sign appears between six and nine weeks post injury²⁵ with the lucency thought to represent hyperemia from a metabolically active, vascularized talar dome (Figure 22.8). The lucent line does not have to span the whole width of the talar dome in order to be deemed present. Tezval et al.²⁵ found the presence of this sign to be a reliable prognostic indicator that avascular necrosis will not develop at a later stage. However, conversely the absence of a Hawkins sign does not dictate that the talus is avascular.

Figure 22.8 (a, b) Closed extrusion of the talus. (c) Six weeks after open reduction of the talus with Tightrope^® (Arthrex) stabilization of the syndesmosis. Note the very sclerotic appearance of the talar dome. (d) Three months post injury. Note Hawkins’ sign suggesting re-vascularization of the talus.

Lateral Process Fractures

Lateral talar process fractures account for approximately 25% of all talar fractures. They are frequently high-energy injuries and result from an everted or externally rotated foot being forced into dorsiflexion – a mechanism of injury typically associated with snowboarding²⁷. There is commonly an associated dislocation of the ankle or subtalar joint (Figure 22.9). In those injuries where there is no concurrent dislocation, the radiographic findings can be subtle, and the fracture is easily missed. Although Broden’s views, with the leg internally rotated 45° and the x-ray beam tilted 10 to 40° to the head, increase the likelihood of making this diagnosis, a CT scan more accurately assesses the fracture.

Figure 22.9 (a, b) Plain radiographs of a lateral process fracture with subluxation of both the ankle and subtalar joints. (c) Postoperative radiographs showing reduction and fracture fixation.

Lateral talar process fractures were also classified by Hawkins²⁴:

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  Type I – simple two-part fracture

  
  
• 
  

  Type II – comminuted fracture

  
  
• 
  

  Type III – chip fracture of the anteroinferior lateral process.

Type I and type III fractures can be managed in a non-weightbearing cast, if they are undisplaced. In those lateral process fractures associated with a dislocation, the injury is frequently irreducible, necessitating open reduction. A lateral subtalar approach affords excellent access²⁷. In order to confer stability and to lessen the risk of non-union, internal fixation of the process is recommended in fractures displaced by more than 2 mm (Figure 22.9)²⁸. In comminuted fractures where the fragments measure less than 1 cm, the fragments should be excised.

Fractures of the Talar Neck

These fractures are usually high-energy injuries, which are associated with polytrauma, where dorsiflexion in conjunction with supination of the foot results in a fracture of the talar neck. A small number of fractures occur as a result of a heavy object falling onto the dorsum of the foot. Approximately 20% of these fractures are open with many of the remainder having compromised skin and soft tissues^{24, 29}. Nearly a quarter of these fractures are associated with a medial malleolar fracture²⁴.

Hawkins initially devised a classification with three discrete groups of increasing severity²⁴. A fourth group was later added by Canale and Kelly (Figure 22.10), which represents the most severe fracture dislocation of the head of the talus from the talonavicular joint²⁹. The Hawkins–Canale classification system is useful as it reflects injury severity, which helps when counseling the patient about prognosis and functional recovery. Vascular damage occurs with greater displacement, and when it does occur the vessels within the tarsal canal are principally affected.

Figure 22.10 Combined classification of fractures of the neck of the talus according to Hawkins²⁴ and Canale and Kelly²⁹. (a) type I; (b) type II; (c) type III; and (d) type IV.

Type I fractures are undisplaced with a vertical fracture line through the neck extending onto the inferior aspect of the talus between the middle and posterior subtalar facets.

In type II fractures, there is associated dislocation or subluxation of the subtalar joint. The primary fracture line is vertical and sometimes extends into the posterior facet. The dorsiflexion force applied to the talar neck is often associated with rotation and, although in most instances the talar body fragment dislocates posteriorly, the body fragment can also dislocate either medially or laterally.

In type III fractures, the vertical fracture line involves the posterior facet (Figure 22.11). The body fragment dislocates from the ankle mortise and the subtalar joint, either to adopt a rotated position within the mortise or occasionally to twist on the intact fibers of the deep deltoid ligament, and comes to lie posterior to the posterior malleolus and medial to the tendo Achillis.

Figure 22.11 (a, b) Plain radiographs demonstrating a closed Hawkins type III fracture of the neck of the talus. (c, d) Postoperative images demonstrating a medial malleolar osteotomy and two lagged screws inserted percutaneously from a posterolateral approach. Note the postoperative immobilization in a monolateral external fixator to permit easy management of the soft tissue envelope.

Type IV fractures are rare, and only small case series are reported^29–30. A vertical neck fracture is associated with extrusion of the body and, in addition, the talar head dislocates from the talonavicular joint. This group of fractures had a universally poor outcome in Canale and Kelly’s series, although better results have been reported in other series³⁰.

The principles for treating talus fractures are outlined in Table 22.3.

Table 22.3 Principles in treating talus fractures

• 
  

  Make correct diagnosis early

  
  
• 
  

  Maintain appropriate lateral and medial column length

  
  
• 
  

  Maintain appropriate relationship between the forefoot and the hindfoot

  
  
• 
  

  Preserve talonavicular joint function

  
  
• 
  

  Preserve the fourth and fifth tarsometatarsal joints

  
  
• 
  

  Use stable fixation to maintain anatomic reductions or primary arthrodeses

  
  
• 
  

  Allow adequate time for bone and soft tissue healing

Surgical Approaches for Talar Neck Fractures

The single most important factor determining surgical approach is the fracture pattern. Care must be taken not to shorten the talus when there is comminution, and as comminution of the medial wall is commoner, an anteromedial approach is often necessary. In many instances, judging the quality of the reduction necessitates a combined anteromedial and anterolateral approach, although an Ollier approach is an alternative^31–33. Vascular studies confirm these approaches are safe although a previously unidentified medial branch to the talar neck is at risk with the anteromedial approach².

It should also be borne in mind that, as primary open reduction and internal fixation is indicated in all open fractures³², the traumatic wounds are an important determinant of the surgical approach. In the authors’ experience, using the same technique as in pilon fracture fixation³⁴, where the incision is placed directly over the displaced fracture line, avoids further periosteal stripping with disruption of the remaining blood supply to the fracture fragments and permits accurate reduction of the most displaced and comminuted elements of both talar and navicular fractures.

In the anterolateral approach, there is an area bare of arterial supply on the lateral talar neck, which permits safe surgical access without compromising the branches from the anterior tibial or the artery of the tarsal canal. It is important to avoid unnecessary dissection, either plantar or dorsal, on the talar neck to preserve the anastomotic vessels².

Medial malleolar osteotomy is less damaging, and therefore preferable to a wide soft tissue dissection when restoring medial talar neck length². Lateral malleolar osteotomy, similarly, does not compromise the talar blood supply². Medial malleolar osteotomies are more likely to be required than lateral malleolar osteotomies in order to aid reduction of type III talar neck fractures and in fractures involving the talar body³⁵ (Figures 22.12 and 22.13). It may also be possible to use a malleolar fracture to access the talus (Figure 22.14).

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Chapter 1 – Clinical Examination of the Foot and Ankle Chapter 11 – Sports Injuries of the Foot and Ankle Chapter 9 – The Cavus Foot Chapter 15 – Disorders of the Tendo Achillis Chapter 17 – Benign Tumors of the Foot and Ankle Chapter 3 – Radiology of the Foot and Ankle

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