KEY FACTS
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The talus is the 2nd most commonly fractured tarsal bone (after the calcaneus).
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The blood supply of the talus can be tenuous, as there are limited spaces at which vessels can enter the bone, given its morphology and participation in multiple joints.
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The blood supply of the talar body is retrograde through the talar neck.
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Although there is great concern for osteonecrosis after talar neck and body fracture, posttraumatic arthritis is a more common outcome.
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Posttraumatic arthritis is likely related to the initial severity of the injury but also the quality of the ultimate reduction, and every effort should be made for as anatomica reduction as possible.
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For the rare posteromedial talar body fracture, it is important to understand that medial malleolar osteotomy is not helpful and does not improve visualization, as the fracture line is typically posterior to the medial malleolus.
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Lateral process talus fractures are increasingly common and should be considered in the setting of an acute ankle sprain.
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While nonunion is rare after talar neck fracture, malunion, especially varus malunion, is not. Compression of a comminuted medial talar neck should be avoided in an effort to minimize the risk of this complication.
Background
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Talus fractures fall into a difficult middle ground of injuries that are infrequent enough that they are difficult to study but frequent enough and often severe enough that they cause significant functional morbidity for a number of people that is not insignificant.
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Injuries are typically high energy, such as a fall from a height or a motor vehicle accident. As with any high-energy injury, initial evaluation consists of a thorough clinical examination with a search for other injuries.
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As the talus is mostly covered with articular surface, any significant fracture displacement requires a joint subluxation or dislocation. In other words, most displaced talar fractures are also dislocations.
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All dislocations should be reduced emergently to prevent further soft tissue injury. Historically, these injuries, especially talar neck fractures, were treated emergently, as this was thought to decrease the risk for osteonecrosis (ON), although more recent data suggests that this is likely untrue.
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Radiographic examination consists of anteroposterior, lateral, and mortise images of the ankle and anteroposterior, lateral, and oblique views of the foot. Canale views are beneficial and can increase the ability to visualize the talar neck.
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Computed tomography (CT) scanning of talus fractures is crucial; it aids in understanding the extent of injury as well as being critical for surgical planning. Imaging studies should be carefully reviewed for the presence of other fractures of the foot or ankle.
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Anatomy
Introduction
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“Talus” comes from taxillus, Latin, which means dice. The Romans used the heel bone of the horse to make dice. The Greeks used the 2nd cervical vertebrae of sheep to make dice, and astragalus is vertebra in Greek.
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2/3 of the talus is covered by articular cartilage. There are no tendon or muscular attachments to the talus, but many muscles cross the talus, all of which also influence the subtalar and other hindfoot joints.
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It is a weight-bearing bone that transfers all the weight from the foot to the tibia and fibula. For descriptive purposes, it is divided into the body, neck, and head.
Talar Body
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The body includes the talar dome and posterior facet, which make up the ankle and subtalar joints, respectively. The superior portion of the body is articular. It is shaped like a pulley in the coronal plane with the trochlear portion lying offset more medially. In the axial plane, the superior surface is shaped like a trapezoid with the anterior portion wider than the posterior.
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The lateral talus becomes somewhat triangular and articulates with the fibula. The perimeter of the lateral articular portion is called the lateral process. It serves as the site of attachment for the lateral talocalcaneal ligament as well as the anterior and posterior talofibular ligaments. The undersurface of the lateral process makes up the lateral portion of the posterior facet of the subtalar joint, so that most lateral process fractures are intraarticular.
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The medial portion of the talus has a large articular surface for the medial malleolus. In the anterior nonarticular area, there are vascular foramina. The posterior body serves as insertion for the deep deltoid ligament.
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The posterior process of the talus is made up of posteromedial and posterolateral tubercles, between which lies a groove for the flexor hallucis longus tendon.
Talar Head
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The head primarily articulates with the navicular anteriorly. Inferiorly in the head are the anterior and middle subtalar facets, which are sometimes fused into a single facet. These joint surfaces make a socket in which the talar head rotates (or, more accurately, the socket rotates around the talar head). There are attachments for the spring ligament, deltoid ligament, and sustentaculum tali.
Talar Neck
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The neck lies between the body and head and has multiple ligamentous attachments. It is oriented 15-20° medial to the talar body and lies directly over the sinus tarsi and tarsal canal. This region has numerous capsular attachments and vascular foramina.
Vascular Anatomy
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The vascular supply of the talus has been of special interest due to association of ON with talus injuries.
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Since 2/3 of the talus is covered by articular cartilage, and there are no muscular attachments, the blood supply is limited. There are contributions from the capsular and ligamentous attachments to the tibia, calcaneus, and navicular.
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Extraosseous Arterial Supply
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Branches of the posterior tibial, dorsalis pedis, and peroneal arteries contribute to the talus; however, there are multiple variants on the branches. There is a delicate network of anastomoses between the arteries, which envelops all the nonarticular areas of the talus.
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The posterior tibial artery gives off the artery to the tarsal canal and a vascular plexus for the posterior process. The deltoid branch of the artery to the tarsal canal supplies the medial talar body.
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The dorsalis pedis leads to the anterior lateral malleolar artery and branches over the superior surface of the neck to supply the head. The anterior lateral malleolar artery anastomoses with the peroneal artery supply to form the artery of the tarsal sinus.
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The peroneal artery sends branches to the posterior process to anastomose with the posterior tibial vessels. In addition, it contributes to the artery of the tarsal sinus via the perforating peroneal artery.
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The arteries of the tarsal canal and sinus anastomose, forming the artery of the tarsal sling. This supplies the inferior neck and lateral body. The arteries of the tarsal canal and sinus, along with the medial periosteal vessels, are the most essential supply to the talus.
Intraosseous Blood Supply
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The head receives its blood supply from the dorsalis pedis superiorly and artery of the tarsal sling inferiorly.
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The talar body blood supply enters the bone in 5 places.
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These vessels enter in those areas without articular cartilage:
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Anastomosis between posterior tibial and peroneal branches at posterior process
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Superior surface of talar neck
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Inferior surface of talar neck
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Anterolateral surface of talar body
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Medial surface of talar body (from deltoid ligament)
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The artery of the tarsal canal supplies the lateral 2/3 of the talar body, while the deltoid branch supplies the medial 1/3. There are also multiple intraosseous vascular anastomoses between the supplying arteries.
Talar Body Fractures
Background
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These are typically, but not necessarily, high-energy injuries. Inokuchi et al defined the difference between talar neck and body fractures based on the inferior articular surface of the talus. If the major fracture line exits at or posterior to the lateral process, it is considered a body fracture. Thus, talar body fractures are intraarticular ankle and subtalar joint injuries. Fractures that exit anterior to the lateral process are neck fractures.
Evaluation
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As these are often high-energy injuries, a full secondary survey should be performed. Radiographs typically do not demonstrate the full extent of articular injury and comminution; therefore, CT imaging is required. The full degree of articular and cartilage injury often cannot be fully appreciated until the time of surgery.
Treatment
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Nonoperative treatment is reserved for those fractures that are completely nondisplaced. Even then, many surgeons will still opt for internal fixation to allow for early range of motion exercises.
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Emergent surgical treatment is necessary in all open injuries and in all dislocations that cannot be reduced, with irrigation and debridement of open wounds, and reduction of dislocations. Definitive reduction and fixation can wait.
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For the definitive surgery, anatomic reduction with stable fixation is the goal. Fragment specific fixation is often used.
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Surgical approach is dictated by the area of injury.
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A medial approach through the interval between the tibialis anterior and the tibialis posterior is often required. This approach can be extended proximally to incorporate a medial malleolar osteotomy for greater visualization of the medial talar dome. The medial malleolus is predrilled for lag screws prior to the osteotomy.
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An anterolateral Ollier-type approach can be used for lateral visualization.
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After provisional fixation, the reduction should be critically assessed. Once anatomic reduction is confirmed, final fixation is placed. It is occasionally necessary to countersink screw heads into the articular cartilage. The type of fixation used is much less important than the quality of reduction. Bone grafting is occasionally required to support articular segments that have been disimpacted.
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Postoperatively, the patient is splinted for 2 weeks, then a CAM boot is applied. With stable fixation, range of motion is begun at 2 weeks after surgery. All patients should remain non-weight bearing for 6-8 weeks depending on the injury.
Outcomes
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Outcomes are often dictated by the severity of the initial injury, quality of joint reduction, and degree of articular injury.
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Posttraumatic arthrosis, malunion, and ON are more common in severe crush injuries and are associated with the severity of the initial injury.
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Sneppen et al reviewed 21 patients with talar body fractures. Eighteen of these fractures were treated nonoperatively, and 3 underwent open reduction and internal fixation (ORIF). In this series, 60% of the patients had malunion. The subtalar and ankle joints were found to have very high rates of posttraumatic arthritis. 95% of patients had moderate to severe complaints.
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Vallier et al reviewed clinical, radiographic, and functional outcomes after operative treatment of talar body fractures. ON was observed in 10 of 26 patients, 5 advanced to collapse, while the other 5 showed signs of revascularization. Higher rates of ON were observed in open fractures and those with associated talar neck fractures. Posttraumatic arthritis was reported in 65% of tibiotalar joints and 35% of subtalar joints. Twenty of 30 patients returned to prior level of employment. Eight patients did not return to work. Worse outcomes were found with fractures with open injuries and associated talar neck fractures.
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Lindvall et al found no difference in union rates, ON, posttraumatic arthritis, or American Orthopaedic Foot and Ankle Society outcome scores between fractures of the talar neck and body. Posttraumatic arthritis was a more common finding than ON.
Posteromedial Talar Body Fractures
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Fractures of the posteromedial aspect of the talus represent a rare variant of talar body fractures. The radiographic findings are subtle and can be missed without a thorough review of the radiographs. In several case series, > 50% were missed initially.
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Results of nonoperative treatment for this injury are poor with arthrodesis rates as high as 83%. Like all talar body fractures, they involve both the tibiotalar and the subtalar joints. CT evaluation greatly improves understanding of the extent of injury.
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Due to unacceptably high rates of posttraumatic arthritis with conservative treatment, displaced fractures should be treated with ORIF or excision of the fragment if it is small.
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The fracture cannot be adequately visualized with a medial malleolar osteotomy, as the majority of the injury is further posterior than can be visualized with this surgical approach.
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One option is to position the patient prone and approach the posteromedial aspect of the talus through the interval between the Achilles tendon and the flexor hallucis longus. The authors prefer an approach with the patient supine, utilizing the interval between the posterior tibialis and flexor digitorum longus. Visualization of the relationship of the tendons to the fracture, especially on the axial images, can be greatly beneficial in terms of preoperative planning.
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There is a limited area of extraarticular surface on the posterior talus, and fixation can be problematic. Headless screws can be helpful.
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Postoperative care consists of non-weight bearing for 6 weeks with initiation of ankle and subtalar range of motion exercises at 2 weeks. There is a lack of long-term data on these rare injuries.
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