NB This page is from the 2005 Hyperbook.
Last evidence check February 2005.
Fractures of the talus are rare, making up less than 1% of fractures in general trauma practice and 2% of practice in a level 1 trauma centre (Elgafy 2000). However, they are difficult to treat, with a high rate of poor outcomes and complications.
The talus participates in the ankle, subtalar and talonavicular joints, acting as a link between the vertical shank and the obliquely horizontal hindfoot. It serves as an attachment for many ligaments but no muscles, and over 70% of its surface is covered by articular cartilage. Its circulation is therefore somewhat precarious. Blood reaches it from the posterior tibial, dorsal and peroneal arterial trees, entering on the ligaments and the rough area of the neck from an anastomosis in the tarsal canal. The blood supply of the body mostly reaches it by a retrograde route from the neck and is at risk from talar neck fractures. Petersen showed that, in cadaver specimens, increasing fracture displacement produced greater compromise to the blood supply.
The majority of talar fractures are caused by high-energy trauma such as motor vehicle accidents and falls from a height. The fracture is sometimes known as “aviator’s astragalus”, from wartime series which described talar fractures sustained in air crashes.
The pathomechanics are somewhat controversial. Traditionally it has been held that fractures of the body and neck are caused by forced dorsiflexion against the anterior lip of the tibial plafond – this was thought to be due to impact from an aircraft rudder bar. However, biomechanical work by Petersen showed that talar neck fractures were reliably produced not by dorsiflexion but pure vertical shear against the plafond.
About 25-35% of talar fractures affect the lateral or posterior processes only; of the rest, fractures of the neck are about twice as common as fractures of the body, and about 10-20% are combined fractures of neck and body.
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| fracture of the neck - fracture line anterior to subtalar joint | fracture of the body - fracture line posterior to subtalar joint | combined neck/body fracture -fracture lines anterior and posterior to subtalar joint |
The lateral process is the attachment of the lateral talocalcaneal ligament and the subtalar joint capsule. It may be avulsed by inversion injuries, although some injuries probably have a rotational component. It is particularly associated with snowboarding injuries, hence the name “snowboarder’s ankle”.
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| Fracture lateral talar process - plain film L, CT R | |
Clinically it has the same appearance as a major lateral ligament injury of the ankle – lateral pain, swelling and bruising. Hence it tends to be an incidental finding at radiography of an injured ankle which is failing to settle, and is often missed initially. Plain radiography may underestimate the size and significance of the fragment, and CT is useful if there is a possible intention to fix the fracture. Arthroscopy allows assessment of the subtalar joint, and can be used to assess fracture reduction.
Acutely, some large fragments carry a substantial proportion of the subtalar joint surface and warrant ORIF to minimise the risk of post-traumatic OA. Large, displaced fragments presenting late may already have significant OA and require a subtalar fusion. Smaller, painful, fragments may be excised and the ligament repaired.
The posterior process has a smaller medial and a larger lateral tubercle, separated by the groove of FHL. The process has a separate ossification centre and may remain a separate bone, the os trigonum. A fibrous union between the talar body and an ostrigonum may be injured. The posterior process is an attachment for the posterior talofibular and posterior tibiotalar ligaments.
Fractures of the posterior process may be produced by forced plantarflexion with a “nutcracker effect” between the posterior tibial plafond and the calcaneum, or by a twisting injury that subluxes the subtalar joint or avulses the ligamentous attachments. The lateral process is more commonly injured and is known as Shepard’s fracture from the original description.
Like lateral process fractures, posterior process fractures may range in size, from small avulsions up to large fragments which carry a large amount of the posterior subtalar and ankle joint surface and may lead to arthritis of both joints.
They tend to present acutely simply as a severely injured ankle joint; in our experience localised posterior pain is not usually detectable in the acute stage. They may be picked up incidentally at this stage on ankle radiographs. More often, the fracture presents with persistent posterior, posteromedial or posterolateral ankle pain, posterior impingement or mechanical symptoms. Pain on dorsiflexion or resisted plantarflexion of the hallux suggests FHL injury, compression or tendonopathy. Two of our patients had a tibial nerve injury at presentation. CT is useful to assess the fragment size but the FHL tendon is best assessed with ultrasound or MR. Arthroscopy allows assessment of the ankle and subtalar joints, and has been reported as useful in fracture reduction.
Acutely, small fragments can be managed non-operatively with as much early mobilisation as the stability of the ankle-hindfoot complex will stand. Larger fragments are reduced through a posterior approach and fixed, protecting the FHL and neurovascular bundle. Small fragments presenting late may be symptomatic enough to warrant excision. Large fragments presenting late often have significant subtalar joint surface damage requiring subtalar or even tibiotalocalcaneal fusion, although a few can be reduced and fixed.
Inokuchi defined a fracture of the talar neck as one in which the main fracture line exited the inferior cortex of the talus anterior to the posterior subtalar facet. Nevertheless, some fractures have both neck and body components. Fractures of the neck are about twice as common as fractures of the body. Most are caused by high-energy injuries. One third have malleolar fractures, and fractures of the tibia, calcaneum, midfoot and forefoot are common.
Hawkins divided talar neck fractures into:
Canale added a fourth group with subluxation/dislocation of the ankle, subtalar and talonavicular joints
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| Hawkins 1 - undisplaced | Hawkins 2 - subtalar joint displaced | Hawkins 3 - ankle and subtalar joints displaced | Canale/Hawkins 4 - ankle, subtalar and talonavicular joints displaced |
Higher grade fractures are more commonly open, occasionally with total extrusion of the talar body, and have a higher incidence of avascular necrosis (and possibly compartment syndrome and nerve injuries).
There is an AO universal classification which is rarely used.
Patients usually present with a high-energy injury to the foot and ankle, often with other injuries. The injury may be open. The patient should be assessed for nerve and vascular injuries and compartment syndrome.
A few patients present with a lower-energy injury and may be suspected of having a ligament injury or malleolar fracture – indeed, the diagnosis is occasionally delayed until a presumed ligament injury fails to settle and imaging is obtained.
Clinical assessment of the whole patient is essential. Plain AP and lateral radiographs will usually make the diagnosis; in the presence of major derangement they may be difficult to interpret. A CT is often useful to assess the extent and severity of the injury, aid the decision on whether to offer surgery and inform the operative plan. We would be reluctant to operate for a talar fracture without a CT, except in emergency.
A difficult delayed diagnosis may be helped by isotope scanning and/or MR – both will also give additional information about vascularity.
After fixation, CT can be useful to assess reduction and union, and isotope scanning or MR vascularity or infection, provided (in the case of CT and MR) that non-ferromagnetic implants have been used.
Initial resuscitation, pain relief, treatment of open wounds and temporary splintage are generally applicable to all serious injuries.
Undisplaced fractures are often treated in casts in neutral or plantarflexion with non-weightbearing till radiographic fracture union. Surgical fixation has been suggested to allow early movement, if not weightbearing. No comparative studies have been reported.
Displaced fractures are normally reduced and surgically stabilised:
Temporary closed reduction and splintage may allow the tissues to recover and allow ORIF, but few modern series have reported the results of closed reduction and casting as definitive treatemnt; open surgery seems unlikely to be challenged as standard of care.
An anteromedial approach is most commonly used; an anterolateral approach gives access to what is usually the less comminuted side of the fracture. Recent series have used a combination of anteromedial and anterolateral approaches with improved access but no increase in AVN.
Biomechanical studies suggest that posterior to anterior screw insertion gives best compression; indeed, this was the only configuration that had enough shear strength to resist physiological loading. However, posterior screw insertion with anterior fracture exposure is awkward with the risk of nerve injury. Therefore, screw insertion through an anterior approach is common. Recent studies have suggested the use of mini-fragment plates to bridge comminution and reduce the risk of varus malunion.
Post-operatively, fractures are initially splinted for a variable time before movement is permitted; most modern series seem to have permitted movement within a few weeks of surgery. No biomechanical or comparative clinical evidence is available to tell how long movement should be delayed, if at all.
Weightbearing is usually not permitted until the fracture is radiologically united, usually at 2-3 months.
Fractures of the talus are serious injuries. Most patients have some degree of long-term reduction of foot and ankle function. Both Vallier and Sanders found that about 70% returned to their previous work, some times with some modification. Overall function is most accurately predicted by the severity of the initial injury, with open, comminuted fractures of high Hawkins-Canale grade doing worse even with good treatment. Residual varus also predicted a poor result in one series.
Osteoarthritis of the ankle and subtalar joint is common after displaced fractures. Elgafy considered it contributed more to the outcome than osteonecrosis, but most other authors both factors are of considerable significance. While patients with OA have, on average, poorer functional outcome than those without, some of this is predicted by original injury severity and some patients with severe arthritis have few symptoms. OA can usually be salvaged successfully by fusion or ankle replacement, but in the presence of abnormal bone anatomy and vascularity and compromised soft tissues, the patient must be aware of the risks of failure (though the available data do not allow accurate estimation of any increased risk).
The vascular anatomy of the talus means that fractures may cause avascular necrosis. Most series report that the rate of AVN increases with increased Hawkins-Canale grade, and probably also with communition and open fractures. There is a controversy over whether surgical fixation of talar fractures decreases the AVN risk; this is conducted indirectly on data which could have been affected by other factors and small numbers, as there are no RCTs. The risk of AVN in displaced fractures is about 30-60%, with up to 100% in grade IV injuries, but it may occur in up to 10% of apparently undisplaced fractures. AVN is often partial and leads to talar collapse and OA in perhaps half of the patients in whom it occurs – this information is not reported in many studies.
The classical radiological sign of AVN is the Hawkins sign, a subchondral radiolucency in the talar dome. This is interpreted as indicating vascularity and a good outcome. Lindvall reported the sensitivity of the Hawkins sign (for predicting the ultimate development of AVN) as 67% and the specificity as 86%, although it is not clear what the criteria for the diagnosis of AVN were. MR gives a good assessment of AVN, but can overestimate the extent due to oedema.
Traditionally, AVN has been managed by prolonged non-weightbearing in casts or braces, but there is no evidence that this reduces the rate of talar collapse or OA. Some patients will develop end-stage symptomatic OA requiring fusion, sometimes with major bone-grafting; AVN is usually a contra-indication to ankle replacement.
Inokuchi defined a fracture of the talar body as one in which the main fracture line exited the inferior cortex of the talus through or posterior to the posterior subtalar facet. Nevertheless, some fractures have both neck and body components. Fractures of the body are about half as common as fractures of the neck. These are almost all high-energy energy injuries, with 20% of open injuries. Patients often have polytrauma with other limb injuries. There is damage to both ankle and subtalar joints in most cases, and fragments may become detached from their blood supply and develop osteonecrosis.
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Fracture of the body - note double shadows on AP |
After ORIF |
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The majority are shearing fractures with two major components; the main fracture line is coronal or sagittal in approximately equal numbers. About 20% of fractures are comminuted.
The patient presents with a high-energy injury of the ankle region, and often other serious injuries. In such serious injuries, there is a risk of nerve and vascular injury and compartment syndrome, although these seem to be uncommon on the basis of the silence of published series.
AssessmentPlain radiography will usually give the diagnosis, although in the presence of severe comminution or deformity they may be difficult to interpret. A CT will give a good assessment of fracture severity and anatomy, contributing to the decision on whether to offer surgery, and surgical planning. |
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| CT of bilateral talar body and calcaneal fractures |
Initial resuscitation, pain relief, treatment of open wounds and temporary splintage are generally applicable to all serious injuries.
Displacement of the ankle or subtalar surfaces, open injury, or overall malalignment, would generally be considered indications for ORIF. Undisplaced fractures seem to be uncommon. A few fractures are so severely comminuted that there seems little point in trying to reconstruct them acutely.
Access may be possible through anterolateral and/or anteromedial approaches. However, more posterior fracture lines or comminution may require medial or lateral malleolar osteotomy. Indeed, some of these injuries have associated malleolar fractures which are not necessarily convenient for access to the talus.
Fixation is normally with lag screws which may have to be countersunk to prevent impingement. Headless screw designs are available but may not give enough compression.
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| Severe, extruded body fracture with tibial nerve injury | ||
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| ORIF using medial malleolar osteotomy | 3 months, talus healed with AVN affecting body and medial malleolus | |
Talar body fractures are severe injuries which usually result in some functional reduction. Vallier found that about 2/3 of patients returned to their previous work. The main outcome predictor is the severity of the original injury as expressed by comminution and the presence of an open wound.
Most patients develop some osteoarthritis of the ankle and/or subtalar joint. 38% of Vallier’s patients developed osteonecrosis and half of these had talar collapse. However, it is not clear how many of these patients needed further surgery. Vallier’s series included two amputations for severe initial injuries and five subtalar, ankle or triple fusions.