Talus Fractures
David J. Hak, MD, MBA
Murphy P. Martin III, MD
Dr. Hak or an immediate family member serves as a paid consultant to or is an employee of Bioventus, Globus Medical, and Invibio and serves as a board member, owner, officer, or committee member of the Orthopaedic Research Society and the Orthopaedic Trauma Association. Neither Dr. Martin nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.
ABSTRACT
Talus fractures are relatively uncommon injuries and can be challenging to treat. The unique anatomy of the talus with regard to blood supply and complex surrounding articulations is critical to understand in terms of injury prognosis and surgical planning. Fractures of the talar neck and body are encountered following high-energy trauma and can result in complications such as osteonecrosis and posttraumatic arthritis, which can be difficult to treat. Reconstructive options to address osteonecrosis of the talus are the subject of ongoing research. Fractures of the lateral and posterior processes of the talus can also occur and can be difficult to diagnose, often requiring CT imaging.
Introduction
Talus fractures are uncommon injuries representing only 3% to 6% of all foot fractures.1 Talar neck and body fractures commonly result from high-energy trauma and therefore have a high rate of associated injuries. In addition, the high-energy trauma that produces displaced talar neck fractures frequently damages the limited blood supply to the talus and often causes varying degrees of articular cartilage damage. Talar process fractures are more commonly isolated injuries from lower-energy accidents. The talus has a unique anatomic shape with three-fifths of its surface covered by articular cartilage. The talus has seven separate articular surfaces that form complex articulations with the tibia, fibula, calcaneus, and navicular. The calcaneal articular facets form the subtalar joint. The posterior process of the talus comprises approximately 25% of the subtalar joint. The anteromedial trochlear surface, central trochlear surface, and lateral process form the talar portion of the ankle joint. The talus is held in position by the bony constraints of the medial and lateral malleolus, and by constraining ligaments of the ankle joint. The smallest cross-sectional area of the talus is in the region of the talar neck, which is covered with a relatively weak cortex, making it more susceptible to fracture during high-energy injuries.
Talar Neck Fractures
Mechanism of Injury
Talar neck fractures are usually caused by high-energy trauma, because the thick subchondral bone requires high forces to produce a fracture. The fracture mechanism is most commonly caused by a hyperdorsiflexion force.
Classification
The Hawkins2 classification is the most widely accepted classification system for talar neck fractures (Figure 1). It is based on displacement and dislocation and therefore correlates with the presumed talar blood supply damage. The Hawkins classification was expanded by Canale and Kelly who added the type IV group.3 A Hawkins type I fracture is a nondisplaced fracture, without subluxation or dislocation. A Hawkins type II fracture is a displaced vertical talar neck fracture with a subluxation or dislocation of the subtalar joint. A Hawkins type III fracture is a displaced fracture extending through the talar neck with dislocation at both the subtalar and tibiotalar joints. The type IV category consists of a dislocation of the ankle and subtalar joint, along with a dislocation or subluxation of the head of the talus at the talonavicular joint. The degree of displacement and dislocation is thought to be the primary determinant of blood supply damage and therefore of the risk for the development of osteonecrosis.
Vallier has further subdivided the type II classification into two subtypes: type IIA, which are those with a subluxated subtalar joint, and type IIB, those with a dislocated subtalar joint.4 In their series of 81 talar neck fractures, none of the 19 Hawkins type IIA fractures developed osteonecrosis, but 4 of 16 Hawkins type IIB fractures (25%) developed osteonecrosis.
 FIGURE 1 Schematics showing modified Hawkins classification of talar neck fractures. |
Radiologic Evaluation
Routine ankle radiographs (anterior-posterior, mortise, and lateral views) are used to identify talar fractures. The Canale oblique view of the talar neck provides the best evaluation of talar neck angulation and shortening3 (Figure 2). This view is obtained with the ankle in maximum equinus and the foot pronated 15° while the x-ray tube is angled 75° from the horizontal plane. If plain radiographs do not clearly identify a fracture in a patient with a high suspicion for a nondisplaced talar neck fracture, then a CT scan should be obtained. Preoperatively, CT scans are also useful for assessing comminution and displacement of the fractures as well as providing accurate images of the ankle, subtalar, and transverse tarsal joints.
An association between talus fractures and peroneal tendon subluxation has recently been reported. Evaluation of preoperative CT scans in 30 patients who underwent talus fracture internal fixation identified dislocation of the peroneal tendon in 8 cases, but in only one of the cases was it diagnosed and treated at the time of fracture surgery.5 The presence of peroneal tendon dislocation was associated with the presence of a fleck sign of the distal fibula, which represents an avulsion fracture at the insertion of the superior peroneal retinaculum. An additional patient, whose preoperative CT images did not show peroneal tendon dislocation, was found to have dislocation at the time of a second surgery, leading to an overall incidence of peroneal tendon dislocation of 30% (9/30). Undetected peroneal tendon dislocations on the initial CT images have also been reported in patients sustaining lateral talar process fractures and calcaneus fractures.6,7 Spontaneous tendon relocation has been reported postoperatively in patients with calcaneus fractures, but whether this also occurs following talus fracture fixation has not been studied.8 The clinical diagnosis of peroneal tendon dislocation in these cases is obviously difficult, requiring clinicians to have a high index of suspicion for the possibility of associated peroneal tendon dislocations when treating both talus and calcaneal fractures.
 FIGURE 2 Schematic showing Canale view to evaluate the talar neck. |
Emergency Treatment and Timing of Surgical Fixation
Historically, talar neck fractures were considered surgical emergencies requiring immediate reduction and fixation to minimize the risk of osteonecrosis. Recent studies, however, have found no correlation between surgical timing and the development of osteonecrosis.
In a retrospective review of 102 talar neck fractures, the authors were unable to find a correlation between surgical delay and the development of osteonecrosis. The mean time to fixation was 3.4 days for patients who developed osteonecrosis compared with 5 days for patients who did not develop osteonecrosis. Instead, they found that osteonecrosis was associated with talar neck comminution and open fracture.9
In another retrospective review of 106 surgically treated talus fractures (76 neck fractures, 25 body fractures, and 5 process fractures), the authors reported that surgical timing did not affect the development of osteonecrosis
or posttraumatic osteoarthritis.10 Open fractures were found to be associated with the development of osteonecrosis or posttraumatic osteoarthritis. Thirty-five percent of the patients (15/43) who developed osteonecrosis or posttraumatic osteoarthritis had open injuries, but in the patients who did not develop osteonecrosis or posttraumatic osteoarthritis, only 16% (10/63) had open injuries. The authors indicated that urgent surgical treatment is necessary for threatened soft-tissue or neurovascular compromise, but that the reduction quality is likely more important than the reduction timing.
or posttraumatic osteoarthritis.10 Open fractures were found to be associated with the development of osteonecrosis or posttraumatic osteoarthritis. Thirty-five percent of the patients (15/43) who developed osteonecrosis or posttraumatic osteoarthritis had open injuries, but in the patients who did not develop osteonecrosis or posttraumatic osteoarthritis, only 16% (10/63) had open injuries. The authors indicated that urgent surgical treatment is necessary for threatened soft-tissue or neurovascular compromise, but that the reduction quality is likely more important than the reduction timing.
A retrospective review of active duty soldiers sustaining combat-related talus fractures found evidence of periarticular disuse osteopenia (Hawkins sign), suggesting an intact vascular supply in 59% of cases despite the average time to fixation of 12.9 days. The authors did not find correlation between delayed timing of fixation and development of osteonecrosis or posttraumatic arthritis.11
A survey performed by Patel et al12 found that most expert orthopedic trauma surgeons do not believe that immediate surgical treatment is necessary for displaced talar neck fractures. Most stated that talar neck fracture surgery can wait more than 8 hours, with a significant proportion stating that even a delay of more than 24 hours is acceptable. Because of the high-energy mechanism and limited soft-tissue envelope, 21% of talar neck fractures are open fractures, requiring emergent surgical débridement and irrigation to reduce the risk of infection.2
Although delayed fixation may be suitable for talar neck fractures, an initial closed reduction of any associated dislocation is still recommended with a goal to achieve near anatomic alignment of the talar neck. Once reduced, the dislocated joint typically stabilizes because of the shape and fit of the articular surfaces and surrounding structures, but the use of both provisional K-wire fixation and spanning external fixation has been described.13 Some authors have advocated the use of external fixator to provide distraction of the ankle joint to unload the talus with hopes to reduce the incidence of osteonecrosis.14,15 However, Besch et al16 concluded that external fixation has no effect on the prevention of osteonecrosis following talar neck fractures.
Open Reduction and Internal Fixation
Surgical treatment is indicated for Hawkins type II, III, and IV talar neck fractures. Although completely nondisplaced fractures can be treated nonsurgically, fractures must be carefully followed with serial radiographs to ensure that the fracture does not displace during treatment. Caution must be exercised during nonsurgical treatment to avoid subsequent displacement and deformity, leading some authors to recommend internal fixation for even nondisplaced talar neck fractures.13 Additionally, internal fixation will permit early ankle and subtalar motion.
Anatomic reduction of both the talar neck and subtalar joint is the goal of talar neck fracture treatment because even minimal residual displacement can adversely impact subtalar joint mechanics.17 It is important to avoid reducing the fracture in supination, pronation, or axial malalignment. Because rotational alignment is very difficult to judge, most surgeons recommend the use of dual surgical approaches, anteromedial and anterolateral, to allow accurate visualization and anatomic reduction of talar neck fractures.18,19 The anteromedial approach begins at the medial malleolus anterior border and extends toward the navicular tuberosity running between the anterior tibial and posterior tibial tendons. The lateral incision begins at the Chaput tubercle on the tibia and extends toward the bases of the third and fourth metatarsals.20 However, the Ollier approach, oblique from the tip of the lateral malleolus to the neck of the talus, is also effective and may permit better control of the lateral process and the anterior part of the posterior subtalar joint.21 If the fracture progresses posteriorly into the body of the talus, a medial malleolar osteotomy has been recommended although this approach is more frequently required for talar body fractures.22
K-wires placed in the talar head and body fragments can be used as joysticks to manipulate the reduction and correct the displacement and deformity. To achieve stable internal fixation and decrease the risk for malunion, at least two screws are required.
Most authors recommend placing screws from anterior to posterior because the entrance site is routinely exposed during the anterior approach13 (Figure 3). However, posterior-to-anterior screw fixation has been shown to be biomechanically stronger in a transverse noncomminuted talar neck fracture model.23 Another biomechanical study compared three anterior-posterior screws, two cannulated posteroanterior screws, and one screw from anterior to posterior and a medially applied blade plate in a comminuted talar neck fracture model. In this study, researchers found a trend toward the anterior-posterior screws having approximately 20% lower yield point and stiffness compared with the posteroanterior screws or blade plate techniques, but this difference was not statistically significant.24 Posterior-to-anterior screw fixation also requires additional posterior approach with potential injury to the peroneal artery and its branches, and screw head prominence can limit ankle plantar flexion. A retrospective review of 24 consecutive talar neck fractures treated by posterior-to-anterior screw fixation reported favorable clinical, functional, and radiographic outcomes.25 Complications included six patients with complaints of numbness or paresthesias in the sural
nerve distribution (five transient, one permanent), one nonunion with hardware failure, one superficial wound infection, one patient with flexor hallucis longus muscle stiffness, and one revision surgery to exchange a screw impinging on the talonavicular joint. However, the authors noted no cases of posterior impingement.
nerve distribution (five transient, one permanent), one nonunion with hardware failure, one superficial wound infection, one patient with flexor hallucis longus muscle stiffness, and one revision surgery to exchange a screw impinging on the talonavicular joint. However, the authors noted no cases of posterior impingement.
 FIGURE 3 Radiographs of a 37-year-old woman who sustained multiple injuries in an automobile versus train accident including a minimally displaced talar neck fracture with subluxation/dislocation of the ankle and subtalar joints. A and B, AP and lateral plain radiograph injury views. C and D, She was initially treated with closed reduction and ankle spanning external fixation, followed by open reduction and internal fixation of the talar neck fracture using dual surgical approaches on postinjury day 5 (AP and lateral radiographs). E and F, AP and lateral radiographs 20 mo postoperatively show no evidence of osteonecrosis, but some narrowing of the joint space is present. |
Placing fixation screws in lag fashion is typically used to compress the talar neck fracture to withstand early ankle and subtalar motion. However, lag screw technique may be contraindicated when there is comminution, especially of the medial column, as it will cause deformity and malunion. When there is comminution, fully threaded, nonlagging screws can be used to maintain the correct neck length.19,26 Bone grafting may be occasionally needed to replace impaction defects and restore the neck length.
Many authors have advocated plate fixation with or without neutralization screw fixation for comminuted talar neck fractures.13,18,19,27 Plate sizes, typically ranging from 2.0 to 2.7 mm, can be placed on the most comminuted column of the talus, either medially, laterally, or bilaterally (Figure 4). In addition to providing longitudinal structural support, they also resist supination or pronation of the distal fragment. The use of lateral minifragment plate fixation to augment medially placed sagittal plane position screws was shown to provide length stable fixation, preventing talar neck shortening and malunion in a series of 26 patients with displaced and comminuted talar neck fractures.28 In this series, posttraumatic arthritis was the most common complication, occurring in 38% of cases. Other complications included osteonecrosis (27% of cases) and nonunion (11.5% of cases). No patients required hardware removal.
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