♦ Talar fractures are uncommon injuries and the outcome is very dependent on the tenuous blood supply
♦ Fixation with absolute stability must be achieved
♦ Osteochondral and process fractures are sometimes difficult to appreciate on plain x-rays. Clinical examination and a high degree of suspicion will help to identify these problems early.
The talus is also known as the astragalus (see aviator’s astragalus, discussed later). The ancient Grecian game of knuckle bones uses five taluses in which one is thrown up and the others are swept up in the hand in different combinations and the thrown talus is then caught before it hits the ground, in the same hand. Talus is the Latin name for the Greek Talos, the bronze giant portrayed in Jason and the Argonauts who was defeated by opening the porthole in his ankle and letting the liquor flow out.
The talus is a remarkable bone. Think of its small size in the context of its function. It has to transmit forces of 4g at heel strike at ordinary walking pace. Consider the forces it transmits when running and jumping. It is surprising that fractures are therefore rare accounting for between 3.4% of all fractures of the foot and only 0.32% of all fractures.
The talus articulates superiorly with the mortise joint of the ankle, inferiorly with the calcaneum, and anteriorly with the navicular. Posteriorly the talus has a posterior process comprised of the medial and lateral tubercles, between which runs the flexor hallucis longus tendon. Laterally the prominence of the lateral part of the posterior facet is called the lateral process (Figures 12.60.1–3.)
The talus has 60% of its surface area covered by articular cartilage and has limited soft tissue attachments and blood supply. An appreciation of the tenuous blood supply is important in understanding the disruption that occurs both at the time of injury and during surgical intervention (Figure 12.60.4). The head and neck of the talus are supplied by periosteal branches from the dorsalis pedis and peroneal arteries. Two-thirds of the body is supplied by the tarsal sinus and tarsal canal arteries. Laterally, the tarsal sinus artery arises from the perforating peroneal artery and dorsalis pedis artery. Medially, the tarsal canal artery arises from the posterior tibial artery within the deltoid below the medial malleolus. Deltoid (ligament) and posterior tubercle branches from the posterior tibial artery also supply the body of the talus. In fracture/subluxations these branches within the deltoid may be the only viable blood supply that remains. Therefore if a medial approach needs to be extended, a medial malleolar osteotomy should be used.
In 60% of cases there is a complete intraosseous anastomosis between all regions of the talus.
As a result of its unique anatomy, fractures of the talus have great potential for morbidity.
Investigations for talar and peritalar injuries are documented in Box 12.60.1.
Fractures of the talar neck are well described; however, the talus is prone to a number of other less well recognized fractures (Box 12.60.2).
Talar neck fractures
Aviator’s astragalus (an anachronistic name for the talus) was a term used to describe talar neck fractures sustained by military glider pilots in crash landings. The Crawford-Adams arthrodesis, which he called the RAF arthrodesis, was developed as a consequence. It was postulated that hyperdorsiflexion of the ankle with impaction of the neck into the anterior lip of the tibia was a likely mechanism. Cadaveric work has demonstrated the role of focal loading of the talar neck and pre-impact bracing in the generation of these fractures.
Half of talar fractures appear in the neck and are basicervical. They usually have an oblique orientation and can be associated with disruption of the subtalar, tibiotalar, and talonavicular joints. Talar neck fractures are commonly described using the Hawkins classification (Table 12.60.1 and Figure 12.60.6). Not only does displacement increase the risk of avascular necrosis (AVN) but malunion will affect hindfoot function due to the complex relationship between subtalar, talonavicular, and calcaneocuboid function. Surgical reduction should be anatomical as malunion is associated with uniformly poor results.
Table 12.60.1 Hawkins classification of talar neck fractures
Risk of AVN
Undisplaced fracture line
Displaced fracture, subluxation or dislocation of subtalar joint
Displaced fracture, dislocation of subtalar and tibiotalar joints
Displaced fracture, disruption of talonavicular joint
Hawkins type I fractures are undisplaced (confirmed with computed tomography, CT) and can be treated non-operatively in a below-knee non-weight-bearing cast for 6 weeks. Fifty per cent of these injuries are not visible on presenting radiographs so the clinician must have a high level of suspicion. Full weight bearing is permitted when radiological union is achieved (trabeculation crossing fracture site), usually 8–10 weeks.
In closed Hawkins type II fractures, closed reduction of the subtalar joint should be performed as a matter of urgency. If the surgeon waits until the swelling settles, reduction will be very difficult.
Surgery is indicated for all displaced fractures as it is associated with malunion and non-union. Malalignment of the talar neck has significant mechanical consequences and is associated with poor outcome. The approach must not further compromise vascularity and therefore the vascular anatomy must be clearly understood. The options involve anteromedial, anterolateral or posterolateral approaches. CT is mandatory and three-dimensional CT reconstruction can be very useful to determine the fracture plane and fragmentation. The anteromedial incision allows insertion of anterior to posterior longitudinal screws and can be extended to include a medial malleolus osteotomy. Reduction may be difficult to judge due to fragmentation and an additional anterolateral incision may be required to ensure reduction. The posterolateral approach allows the insertion of posterior to anterior longitudinal screws. A plate is occasionally required, when there is comminution, to hold the neck out to the correct length and orientation.
Hawkins’s sign is a radiological subchondral zone of osteoporosis on mortise/AP views, seen at 6 weeks post-fracture and is a predictor of retained vascularity of the talus following fracture, see Box 12.60.3.
These fractures should be differentiated from osteochondritis dissecans which is referred to as an infraction (incomplete bone fracture without displacement) with a suspected avascular cause associated with abnormal repetitive loading. They tend to be located on the medial dome and may be bilateral.
Osteochondral fractures are fresh injuries as a result of a single episode of trauma. They may not be visible on initial radiographs and occur frequently in association with ankle ligament sprains. Hence, if an ankle injury fails to settle within a reasonable period of time, further investigation with x-ray and magnetic resonance imaging (MRI) is indicated (Figure 12.60.7). Lesions may occur in up to 6.5% of ankle sprains.
An osteochondral fracture is essentially a divot of bone with overlying articular cartilage. The management depends on the size, location, and symptoms as well as general state of health considerations. The commonest location is the lateral dome and is a shear injury associated with an inversion which subluxes the talus in the mortise. Healing is an issue as the fragment has lost its blood supply and may act as a loose body. The separation may be incomplete or may in fact be a transchondral injury.
An undisplaced lesion may be stable or unstable and MRI scan may help to determine if there is a zone of lucency all around the lesion implying separation. The decision to fix in situ may then depend on whether the lesion is symptomatic or not.
Stability of a fragment offers the best chance of healing be that achieved in a cast or by internal fixation. The author uses CT with three-dimensional reconstruction to evaluate the size and position of the fragment as well as planning a surgical strategy in which it is important to determine if the fragment is to be reached via an arthrotomy (open or arthroscopic) or an osteotomy. The surgical options are to fix, excise, or drill the lesion.
Fixation depends on the size and when possible, the author favours 1-mm screws from the compact hand set. Internal fixation may need to be augmented with casting and protective weight bearing but if fixation is sound then non-weight-bearing range of movement exercises with a night resting splint to prevent equinus contracture, is to be preferred. A 2-month period of non-weight bearing is appropriate and sporting activities are not recommended for 1 year.
Salvage strategies may include drilling the defect to provoke healing with fibrocartilage together with loose body removal. Alternatively the defect can be grafted.
In 1959, Berndt and Harty proposed a staging system based on radiographic findings and Anderson et al. and Ferkel et al. used MRI to classify talar osteochondral injury. Pritsch et al. graded lesions according to articular injury visualized during ankle arthroscopy. These staging systems are summarized in Table 12.60.2
Table 12.60.2 Classification of osteochondral fractures of the talar dome
Diffuse, high-signal intensity
Normal, or softening of cartilage
Semicircular lucent line
Semicircular, low-signal line
Break in cartilage; fragment, no displacement
Subcortical round lucency
High-signal fluid within fragment
Same as 2
High-signal fluid surrounds fragment
Defect talar dome, possibly loose body
Defect plus loose body
* Stage 2a is a variant in which a cyst forms in the subcortical bone
Talar body fractures:
These are intra-articular fractures that will usually require anatomical reduction of the articular surface with internal fixation. The dense trabecular bone frequently allows excellent screw purchase. Again CT scanning is mandatory and the author finds three-dimensional reconstruction useful to plan the approach and determine access to the fragments and hence the need for malleolar osteotomy (Figure 12.60.8).
The outcome of these fractures is generally poor with AVN rates similar to displaced neck of talus fractures. Post-traumatic arthritis is seen to occur frequently but does not always correlate with symptoms.
Snow boarder’s fracture
These are fractures of the lateral process of the talus. The lateral talocalcaneal, cervical, bifurcate, and anterior talofibular ligaments originate from tip of this process. This fracture was seen rarely following falls and motor vehicle accidents but is now increasingly recognized and the incidence is rising. It is believed to occur as a result of dorsiflexion and eversion of an axially loaded ankle. It may mimic a lateral ankle ligament sprain and the injury may not be obvious on initial radiographs. Untreated it can be the cause of long-term disability. Primary surgical treatment may improve the outcome of this injury, reducing the risk of secondary subtalar joint osteoarthritis.
Any patient presenting following a snowboarding injury with lateral ankle pain, especially just distal to the tip of the lateral malleolus needs further investigation. Clinical suspicion of this injury mandates a CT scan (Figure 12.60.9). The author again favours three-dimensional reconstruction as well. This helps visualize the size, location, displacement, and degree of fragmentation of the fracture. This helps answer the question as to whether surgery is feasible.
Although these fractures may present late, the investigation and management are similar. Lateral process fractures are reported to have generally poor outcomes when treated in a cast alone. However, small (<1cm) minimally displaced (<2mm) fragments can be considered for non-weight bearing in a below-knee cast for 6–8 weeks. Large fragments should be stabilized with internal fixation unless truly undisplaced. Displaced multifragmentary fractures not amenable to fixation should be considered for excision.
Fractures of the posterior process
Fractures should not be confused with the os trigonum which is a secondary centre of ossification of the posterior process that has not fused to the body of the talus. It occurs in 7–10% of the population and is corticated and rounded. It can be fractured in its own right and diagnostic difficulties may arise which require CT or even MRI scanning to resolve.
The posterior process is comprised of two tubercles and the undersurface of the combined tubercles articulates with 25% of the posterior facet of the subtalar joint (Figure 12.60.10). Displaced fractures are therefore a potential cause of morbidity and oblique views (30 degrees external rotation) or CT may be required to make the diagnosis.
Fractures of the lateral tubercle are known as Sheppard’s fracture and may present clinically like an ankle sprain but may demonstrate tenderness posterolaterally with pain on movement of the subtalar joint and passive movement of flexor hallucis longus tendon.
Fractures of the medial tubercle, known as Cedell’s fracture, will have a similar clinical presentation but may also present with a lump on palpation behind the medial malleolus.
Displaced fractures are best excised unless so large they can be reduced and fixed with small hand set screws (1-mm diameter). Undisplaced fractures may be treated in a cast, non-weight bearing for 6–8 weeks and although non-unions are rare, persistent painful non-union is best treated by excision of the fragment. Non-union may cause pain on subtalar movement or full plantar flexion.
The literature is limited largely to case reports and fractures are frequently associated with dislocations of the talonavicular joint. They represent less than 10% of talar fractures. The experience is that late presentation is common as the fracture may not be visible on plain radiographs. The consequence of late presentation is degenerative change. Diagnosis depends on a careful physical examination for pain, swelling and tenderness of the proximal medial column of the foot and CT scanning. Pain from degenerative changes may warrant fusion.
Accurate reduction and stable fixation should give rise to satisfactory results. Undisplaced fractures may be treated in a non-weight bearing below-knee cast for 8–10 weeks.
Avulsion fractures of the neck
These are small fractures that may be seen on lateral radiographs and are small irregular, often triangular fragments 2–3mm in size. They represent avulsions of the anterior talofibular ligament (ATFL) and are hence radiological signs of ankle sprains as the ATFL is the commonest ligament to be injured. The treatment is aimed at rapid restoration to function with elevation and compression and ice with early weight bearing with physiotherapy in the form of long extensor and proprioceptive retraining to prevent recurrent instability.
Caution is recommended to avoid missing associated undisplaced talar neck fractures.
Dislocation of the tibiotalar joint, without associated ankle fracture, occurs infrequently. In 90% of cases the talus dislocates posteromedially and in 50% of cases there is an open anterolateral wound. In open injuries in addition to the standard management of an open wound the lateral ligaments can be repaired. In closed injuries reduction and immobilization in a below-knee cast for 6 weeks has been demonstrated to produce good to excellent results.
A subtalar dislocation involves disruption of both the talocalcaneal and talonavicular joints. The calcaneus and foot dislocate medially in 59%, laterally in 23%, posteriorly in 11%, and anteriorly in 7% (Figure 12.60.11). Subtalar dislocation is frequently associated with fractures of the foot (64%) and osteochondral fractures of the talus (47%). Many of these associated injuries will have an adverse effect on the outcome and may not be readily identifiable on plain x-rays.
Subtalar dislocations should be reduced as soon as possible to avoid further compromise of the soft tissue envelope. Reduction will frequently have been performed by emergency staff prior to the first x-rays and therefore subtalar dislocation should be considered in ankle injuries with a history of gross deformity without obvious cause. Closed reduction may require a general anaesthetic and it is recommended that it is performed by applying pressure to the navicular with the knee flexed and foot plantarflexed. Traction on the heel and initial exaggeration of the deformity may be required initially to unlock the talus and calcaneum. Closed reduction may not be possible due to entrapped tendons, ligament, capsule, retinaculum, bony impactions, or neurologic and vascular structures. It is recommended that postreduction CT scan is performed as a matter of routine. The subtalar joint is inherently stable and does not usually require internal fixation. In the absence of identifiable pathology requiring operative intervention, treatment involves a below-knee cast for 4–6 weeks depending on the initial instability. K-wire stabilization should be restricted to unstable injuries and it is important to use stout K-wires and strict non-weight bearing to avoid breakage. Assessment of stability should be performed after removal of the cast and in those cases demonstrating instability a further short period of immobilization is indicated.
The majority of patients will complain of subtalar stiffness and subtalar arthritis is common in the long term. AVN of the talus is rare.
Complete talar dislocation
Complete talar dislocation occurs very rarely and is associated with an open injury in approximately 75% of cases. In addition to standard treatment for open wounds, consideration can be given to reducing the talus and stabilising with K-wires. Although acceptable results have been reported, infection and AVN are common complications requiring secondary operative intervention. Alternatively, primary talectomy can be considered. Results of treatment for this injury are anecdotal.
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