Talus approaches

  • Indication

  • Anatomy

  • Possible approaches

  • Considerations

  • Positioning

  • Reduction and fixation

  • Post operatively

  • References

  • Indication

    Central talar fractures, body and neck

     

    Anatomy

    For details of anatomy see talar neck fractures

  • Bony anatomy

  • Blood supply

  • Bony anatomy

    Anterior view Superior view Medial view
    Posterior view Inferior view Lateral view

     

    Blood supply

    Medial view - blood supply

    Anterior view - blood supply

    Inferior view - blood supply

     

    Considerations

    Preservation of the blood supply is essential, especially in severely displaced or dislocated fractures.

     

    Several factors affect choice of approach used.

    • Visibility (ability to judge accuracy of reduction)

    • Sparing blood supply

    Visibility (accuracy of reduction)

    Often two approaches are required to ensure satisfactory reduction and allow for adequate fixation.

    The medial malleolus osteotomy should be considered if there is any problem achieving a perfect reduction of the dome or of the posterior process.

    The lateral malleolus osteotomy is rarely indicated since moving the foot in maximum plantar flexion generally allows a good view of the anterior half of the lateral side of the dome.

    In contrast, maximum dorsi flexion of the ankle gives a good view of the lateral part of the posterior process with a retromalleolar approach.

    Where the lateral part of the dome is crushed, the lateral malleolus osteotomy may be useful.


    Intraoperative fluoroscopy is mandatory.

    It allows checking of the reduction in some “difficult” regions, like the subtalar joints, and testing of the congruency of the joints to be sure that there is no tilting, with the articular surfaces strictly parallel on each side of the joint.

    It also allows testing of the correct position and length of the screws.

    To demonstrate talar neck - place ankle in equinus, place foot on cassette and pronate 15°, x-ray tube is directed cephalad at a 75° from the horizontal.

     

    Arthroscopy can be useful to check the posterior subtalar joint, to which access is limited.

     

    Sparing the blood supply

    Surgical approaches destroy part of the blood supply, and the surgeon should respect the soft tissues surrounding the bone as much as possible.

    It is important to know the anatomical layout of the blood supply in order to estimate the extent of the blood supply “sacrifice” according to the supposed lesions due to the trauma.
    For example, on the medial side of the neck, the anastomosis between the dorsal neck network, the deltoid branch, and the medial plantar artery branch are generally destroyed by the anteromedial approach but sometimes they have to be preserved.

    On the posteromedial side, care should be taken of the deltoid branch and of the tarsal canal artery.

    From this point of view, the medial transmalleolar approach is less dangerous for the blood supply than an extensive difficult retromalleolar approach.
    In the anterolateral approach, one should preserve at least one of the major sources of the sinus tarsi network, either from the perforating branch of the peroneal artery or from the anterior tibial artery.
    The lateral transmalleolar approach destroys any participation of the perforating branch of the peroneal artery in the sinus tarsi network.

    The screws can also destroy the blood supply in the roof of the canal tarsi, particularly if inserted from behind to the lower part of the head.

    This could explain the necrosis that can occur, even without dislocation, with a theoretically intact posterior blood supply.

     

    Possible Approaches to Talus

    Anterior approach

    The anterior approach between the extensor hallucis longus and the extensor digitorum communis is more an ankle approach.

    It is deleterious to the blood supply, destroying the main sources of blood supply to the head.

    It does not allow any visualisation of the subtalar joints, and is unadapted for correct screw positioning.

    This approach should be avoided.

     

    Anteromedial approach

    For the anteromedial approach, there are three possibilities:

    (1) Along the tibialis anterior tendon, allows good access to the dorsomedial aspect of the neck and the dome, but with difficult visualisation of the anterior subtalar joint.
    (2) The lower anteromedial approach, along the tendon of the tibialis posterior, gives a better view of the anterior subtalar joint, but access to the dome is more difficult. To access the anterior subtalar joint, it is helpful to fix a K-wire in the sustentaculum tali to retract the soft tissues.
    (3) The standard anteromedial approach (solid line) is between the tendons of the tibialis anterior and tibialis posterior. It is a good compromise and it can also be extended by a medial malleolus osteotomy (dotted line), thus giving control over the totality of the medial side of the talus.

     

    Posteromedial approach

    The posteromedial approach is difficult and dangerous.
    It is reserved for fractures of the medial side of the posterior process.

    The incision is retromalleolar and slightly curved.

    The best way to preserve the blood supply of the talus would be behind the neurovascular bundle but generally it is necessary to go close to the tibia, moving the tendons of the tibialis posterior and the flexor digitorum communis.

    Any incision of the posterior part of the deltoid ligament should be avoided to preserve the blood supply.

     

    Anterolateral (Ollier) approach

    For the anterolateral approach, there are two possibilities:

     

    (1)The classical sagittal approach (dotted line), follows the lateral side of  extensor digitorum longus in front of the lateral malleolus, appears to be the more anatomical one.

     

    (2)The Ollier approach (solid line), oblique from the tip of the lateral malleolus to the neck of the talus, is more effective.

    Care should be taken of the lateral branch of the fibular superficial nerve at the upper part of the incision.

    This approach allows better control of the lateral process and the anterior part of the posterior subtalar joint.

     

    Posterolateral approach

    The posterolateral approach is behind the lateral malleolus, between the flexor hallucis longus and the peroneal tendons.

    The sural nerve should be preserved and retracted with the anterior side of the incision.

     

    Medial transmalleolar approach

    The medial transmalleolar approach could be very helpful in some cases.

    It is simple and not deleterious as long as some principles are respected.

    Predrill two parallel holes for later fixation.

    Then make a chevron osteotomy with the tip of the chevron a little above the plafond, and the cuts oblique, descending to the angle between the medial malleolus and the plafond but incomplete, without penetrating the joint; and then break the last few millimeters of bone.
     

    Lateral transmalleolar approach

    The lateral transmalleolar approach, is more difficult, but seldom indicated.

    The fibula can be cut some centimeters above the syndesmosis; then the tibiofibular as well as the talofibular ligaments are cut, and the lateral malleolus is moved with preservation of the calcaneofibular ligament.
    The reconstruction is made with a plate fixation of the fibula, associated with ligament repair and syndesmosis fixation.

    This technique, which allows perfect access to the whole lateral part of the talus, seems to be deleterious for the syndesmosis.
     

    To avoid syndesmosis impairment consider osteotomy below.

    Cut the lateral malleolus obliquely at the level of the talocrural joint, like a B malleolar fracture, and then cut an anterior triangle with the insertion of the anterior tibiofibular ligament.

    This preserves the tibiofibular interosseous ligament and the anterior tibiofibular ligament.

    It is necessary to cut the anterior talofibular ligament to get good exposure of the lateral talar dome.

    The posterior tibiofibular ligament can be cut, if absolutely necessary, to obtain good exposure of the posterolateral part of the body.

    Reconstruction is easy, with one or two lag screws and a plate.

    There is no syndesmosis instability.

     

    Positioning

    Supine

    Bring down bed so feet at very end of bed helps with fluoroscopy.

     

    Reduction and fixation

  • Anatomical reduction

  • Aids to reduction

  • Fixation

  •  

    Anatomical reduction

    It is necessary to see both sides of the fracture to ensure an anatomical reduction.

    With an isolated anteromedial approach the lack of reduction laterally would not be appreciated.

     

    For neck fractures, one can access the medial half of the neck through an isolated anteromedial approach.

    A complementary lateral approach is indicated not only in difficult cases, or where doubt about the accuracy of the reduction exists, but all cases, even so called simple fractures.

    On the lateral side of the neck, there is generally a relatively thickened cortical bone spur, which often provides a key to reduction.

    With an associated anterolateral approach, it becomes possible to detect two potential flaws, even if it looks “anatomical”  on the medial side:

    • An opening of the fracture line (with a loss of contact of the main fragments on the lateral side ie, a varus deformity of the neck)

    • Tilting of the distal fragment in supination or pronation.

    These two common malreductions remain generally unsuspected if you perform an isolated approach since they are very difficult to detect on the postoperative x-rays. They strongly impair the function of the subtalar joint.


    For joint fractures (body of talus), one is generally satisfied once the visible part of the dome looks “anatomically” reduced, often no care is taken to asses the subtalar joints.

     

    The posterior subtalar joint should be checked by the anterolateral approach.

     

    Where indicated the anterior subtalar joint can be viewed through the anteromedial approach with an incision dividing the anterior part of the deltoid ligament to the sustentaculum tali.

    The soft tissues can be retracted by a K-wire inserted into the sustentaculum tali.

    Since direct sight of these joints is not easy, complete checking using fluoroscopy.

     

    Once an anatomical reduction has been achieved, it is maintained by provisional K-wire fixation.

    Care should be taken to avoid secondary displacement when inserting screws.

     

    Aids to reduction

    The AO “femoral” distractor can be very helpful, for the reduction of fracture-dislocations and for the exposure of multifragmentary articular fractures.

    It is inserted on the medial side with one pin in the tibia and one through the calcaneal tuberosity below the neurovascular bundle.
    Where a fracture-dislocation cannot be reduced by hand. Repeated forceful attempts should be avoided since they increase the soft tissue damage.

    In these cases, the AO distractor can achieve  progressive distraction, under fluoroscopic control.

    Once the place of the enucleated fragment is recreated by distraction, it is generally easy to reduce the talar body without needing to open the ankle.

    For the reduction of multifragmentary articular fractures, distraction generally helps by opening the joints to improve the view inside.

    Distraction by a distractor is more effective than manual traction on a K-wire, or a Schanz pin in the calcaneal tuberosity as it can be maintained without movement, allowing precise manouvers on the articular fragments.
    The distraction can be provisionally released when the reduction of a multifragmentary fracture needs to press all the fragments against the surface of the intact corresponding bone, or when mobilization of the joint is necessary, for instance, in maximum plantar flexion.
     

    Provisional K-wire transfixation of a mobile posterior fragment through the posterior subtalar joint can be very helpful.

    The use of a pointed clamp is not always useful, when pushing the anterior fragment against this posterior fragment as it tends to glide out with a ’soap effect’.

    Sometimes, a strong K-wire can be used as ‘joystick’ to correct some tilting of the  head and neck fragment in pronation or in supination. This technique avoids the use of a pointed clamp, which needs a larger exposure with more damage to the vessels.
    The last tool for helping reduction is fluoroscopy.

    For the subtalar joints in particular, on which direct sight is partial, it is sometimes necessary to achieve reduction by manipulating the joints and the fragments under fluoroscopic control.

     

    Fixation

    Screws

    Titanium screws should be used to allow subsequent MRI to detect avascular necrosis.
    Biodegradable screws could be an interesting future alternative to metallic screws.
    Cannulated screws are not as useful as could be expected.

    The guide K-wire cannot be used for provisional fixation. If it is, once drilled, the fixation becomes no longer effective and a slight displacement can occur during screwing. Thus, at least one other K-wire is absolutely necessary to maintain the reduction during screwing. In fact, this provisional K-wire can be used as landmark for positioning a normal screw. Thus, accurate drilling can be done, parallel or not to this K-wire, with fluoroscopic control.
    The screw is then inserted without any fracture displacement.

    The real need for a cannulated screws is in (percutaneous) posteroanterior screwing, which generally can (and should) be avoided.
    Compression is usually needed to achieve strong fixation with an anatomical reduction.

    However it should be avoided in cases with comminution.

    In such cases, the result of inappropriate compression could lead to shortening of the neck or, worse, tilting of the head and neck fragment, by opening the opposite side.

    As a result of these difficulties, lag screws have to be considered with a lot of prudence in the presence of comminution.

     

    If an extrarticular screw is placed into the neck tangentially to bone, the head of the screw comes in contact with the neck early and may displace the distal fragment.

    It is sometimes necessary to insert the screws directly into the cartilage of the head, within the talonavicular joint.

    Whenever possible, this procedure should be avoided since this is the most important joint of the foot. But when absolutely necessary, it can be done with some precautions.
    The head of the screw should always be countersunk, not only into the cartilage, but also into the subchondral bone. So, the full thickness of the cartilage can play a mechanical role above the head of the screw. In such cases, a 2.7 mm screw is preferable since its head is smaller.
    Another option could be the use of headless screws.

    They do not need any enlargement of the drilling hole to be positioned in the subchondral bone and their mechanical properties have been shown to be comparable to those of “normal” screws.
     

    From the lateral side, insertion of the screw is easy if the fracture runs through the anterior part of the body, leaving intact the anterior part of the lateral process.

    In the neck fractures, positioning of the screw could be more difficult. There is generally a kind of intact strong spur, of the neck in the middle of the anterior aspect of the lateral process, which allows a gentle insertion of a small screw.
    Therefore, it is generally possible to fix a fracture of the neck and of the anterior part of the body with at least two screws inserted from each side in convergent directions.

     

    The posteroanterior insertion of screws is exceptionally indicated in central fractures and is not easy.
    There is a narrow place close to the lateral tubercle of the posterior process, between the groove of
    the flexor hallucis longus and the insertion of the posterior talofibular ligament in the horizontal plane
    and between the talocural and the subtalar joints in the sagittal plane.
    The head of the screws should be gently countersunk to avoid any impingement.
     

    There is an increased risk of vascular injury in the roof of the sinus tarsi if the screw is inserted in the direction of the lower part of the head.
    On a dry bone it is easy to see that, if the tip of a posteroanterior screw is situated in the lower half of the head, the shaft of the screw protrudes into the roof of the sinus or canal tarsi. (circle)

    The danger is much greater if the screw is inserted posteromedially, since it destroys the  tarsal canal artery close to its origin.

     

     

    Thus, although mechanical tests advocate posteroanterior screwing, which is generally considered safe for the blood supply, it should actually be contemplated with many precautions, and, at least, absolutely avoid the lower half of the head.

    Intraoperative reference to a sterile plastic model is useful to choose a safe position for the screws. In all cases, positioning of the screws should be checked by fluoroscopy to detect any problems of length and/or direction. Care should be taken not only of the joints, but also of the roof of the sinus or canal tarsi, to avoid any damage to the blood supply.

     

    K-wires

    Normally used for temporary fixation.

    Sometimes, it can be helpful to definitely fix some very thin intermediate fragments according to the “lost K-wire” technique.

    A small K-wire (0.8—1.0 mm) is “precut” to the estimated length, making a notch, with a usual cutter, at approximately the half of the thickness of the wire. The K-wire is then inserted normally with a motor drive, and once the notch reaches the surface of the fixed fragment, the K-wire is bent laterally and broken.

    Therefore, there is no metal sticking beyond the surface of the intermediate fragment, which can be then covered by the other main fragment. This technique should be avoided for the fixation of a small fragment in an isolated osteochondral fracture, due to the eventual risk of migration of the K-wire within the joint.
    Resorbable pins are preferable in such cases. They should be positioned in different directions, to avoid secondary loosening of the fragment within the joint.

     

    Plates

    Until now plates have been rarely used in talar fractures.

    They may be useful in fixing comminuted neck fractures or to fix a malunion osteotomy.

    A new AO locked plate that could be used either on the lateral or the medial side is under development.

     

    Osseous graft

    A cancellous bone graft is used in cases with subchondral bone loss by impaction, or in comminuted neck fractures.

    Subchondral impaction generally involves the dome (especially the posterior part) or the inferior aspect of the head in the anterior subtalar joint.

    Usually, part of cartilage remains in continuity with the intact articular surface as a kind of hinge, which is helpful.
    Reduction is achieved by a gentle leverage with a spatula or a K-wire, as deep as possible in the subchondral bone. Cancellous bone chips are then gently pushed into the bone loss area until the pressure begins to lift the osteochondral fragment to the normal level.
    Resorbable pins, lost K-wire, or fibrin glue, can then achieve complementary fixation.

    In the comminuted neck fractures with bone loss, the cancellous graft is not used for mechanical properties, but to avoid the interposition of fibrous tissue and then improve the bone healing and the blood supply restoration.

     

    Post operatively

    In cases of osteochondral associated lesions, or of articular comminution, use a below knee cast for 4 - 6 weeks.

    In the other cases, if stable fixation is achieved, early postoperative active motion is preferable.
    Motion of the joints improves cartilage healing and motion of the foot improves the blood circulation.
    Partial weight bearing is generally allowed after 6 - 8 weeks and total weight bearing after three months.

    In cases of potential or patent necrosis, prolonged non weight bearing cannot be advised.

    Long-term immobilization can lead to secondary arthrosis.

     


    References

    Injury(2004) 35, S-B10—S-B22; Central talar fractures—therapeutic considerations; Patrick Cronier, Abdelhafid Talha, Philippe Massin

     


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    Last updated 24/04/2006
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