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AO Standard Surgery: Screw Fixation for Displaced Talar Neck Fractures
Anatomy
The blood supply to the talus is severely compromised in fracture-dislocations. The posterior tibial artery gives off branches medially, the dorsalis pedis artery anteriorly, and the peroneal artery laterally. These vessels anastomose via a vascular network within the tarsal canal.
The deltoid branch of the posterior tibial artery must be preserved. It is a critical entry point for blood supply to the medial talus, which is why a medial malleolar osteotomy can successfully protect the talar blood supply.
● The deltoid branch is crucial for the blood supply to the medial talar neck and talar body.
● Branches of the dorsalis pedis artery supply the talar head and most of the dorsal talar neck.
● The artery of the tarsal canal, originating from branches of the posterior tibial artery, supplies most of the talar body.
● The contribution from the peroneal artery laterally is minimal.
Treatment Decision
If a talar neck fracture is nondisplaced and all joint surfaces are well-aligned, nonoperative treatment is a reasonable option.
If the fracture is displaced, it is often associated with other hindfoot injuries, which requires further assessment and formulation of other treatment plans.
Nondisplaced fractures might only require plain radiographs, but this scenario is uncommon; most talar neck fractures have at least some degree of displacement.
CT scan is invaluable when there is doubt about fracture displacement or when debridement of the subtalar joint is needed. With increasing severity of injury, greater displacement typically implies more severe osteochondral damage to the subtalar and tibiotalar joints. Such fractures often require surgical debridement and fixation.
Overview of Closed Reduction
For displaced talar neck fractures with poor soft tissue conditions, closed reduction should be attempted whenever possible. This is because uncorrected deformity can lead to soft tissue and skin compromise. If soft tissue conditions are good and the joint is not dislocated, surgical intervention can be delayed.
Another important reason for early closed reduction of talar neck fractures is the critical importance of blood supply to the talar neck and body. The longer the fracture fragments remain displaced or dislocated, the further the already complex blood supply is compromised.
However, the difficulty of closed reduction increases significantly with the severity of the talar neck fracture. The success rate of closed reduction for Hawkins type II fractures is only 30%-60%. Furthermore, closed reduction does not need to achieve anatomical reduction; its goal is to protect the soft tissues during the period before definitive care.
Closed Reduction Technique
The injured side can be identified by observing swelling and deformity of the foot. Comparing with the patient's normal contralateral foot helps understand their individual anatomy.
The talar body usually remains relatively fixed to the tibia, while the talar head and calcaneus sublux medially or laterally.
Traction
Longitudinal traction combined with reversing the deforming force can assist the reduction maneuver.
If reduction is successful, normal anatomy is restored. The deforming force can be either medial or lateral, depending on the direction of fracture displacement.
Typically, after successful reduction of a Hawkins type II talar neck fracture, the normal foot anatomy is restored. Subsequent assessment requires cast immobilization and radiographic evaluation.
Multiple attempts at closed reduction are not recommended to avoid further soft tissue injury.
Overview of Open Reduction
Hawkins type III talar neck fractures are generally irreducible by closed means, but an attempt should still be made (success rate <25%). The management principles for Hawkins type IV fractures are similar to type III.
Hawkins type II fractures are less commonly open fractures, but 50% of Hawkins type III fractures present as open injuries.
Exposure
For all talar neck fractures requiring surgery, the combination of anteromedial and anterolateral approaches is optimal. These two incisions ensure adequate visualization for reduction and fixation.
Aids during Open Reduction include guidewires, external fixators, small distractors, or laminar spreaders; a headlamp improves visualization, and a C-arm (image intensifier) guides the reduction of this complex fracture.
If reduction cannot be achieved through the standard combined anteromedial and anterolateral approaches, a medial malleolar osteotomy is the most commonly used solution. A modified oblique lateral incision is also an option.
Medial Malleolar Osteotomy requires extending the anteromedial incision to provide access for the osteotomy. Care must be taken to maintain the integrity of the deltoid ligament with the osteotomized fragment to protect the blood supply to the talar body.
Open Reduction Maneuvers
During the procedure, all soft tissue attachments to the talar body (sources of blood supply) must be preserved. A dual-incision approach is usually necessary.
If the combined approach still fails to achieve reduction, proceed as follows: first use periosteal elevators and guidewires, then apply an external fixator and distractor, and finally perform a medial malleolar osteotomy (the most invasive but most definitive method). Each step should be performed under C-arm guidance.
The illustration shows a patient under general anesthesia with full muscle relaxation. A medial distractor is used to achieve reduction of the talar neck fracture through traction, correcting rotational deformity and restoring the talar body to its anatomical position.
The second image shows the talar neck reduction effect with the tibiotalar joint held in distraction.
Fixation
Provisional Fixation
Lateral side: Kirschner wires (K-wires) aid in achieving provisional fixation. Their placement is crucial for definitive screw fixation when using cannulated screws.
The lateral talar neck is usually not comminuted; reduction can be achieved by interdigitation of the fracture fragments. Compression-mode screw fixation is more suitable laterally.
Medial side:
The medial talar neck often has some degree of comminution. Reduction should be performed under C-arm guidance. Fixation should employ a fully threaded cortical screw for positional fixation. If a lag screw is used, tightening may cause medial displacement and shortening of the talar neck.
Medial K-wires are usually best placed through the medial part of the talar head articular cartilage to allow for subsequent screw countersinking.
Screw Fixation
Once K-wire placement is satisfactory and reduction is confirmed accurate with the C-arm, cannulated screws can be inserted over the guidewires.
Due to frequent comminution medially, the lag effect should be avoided. Screws here require non-compression fixation (positional screws). The screw head is typically countersunk at the medial edge of the talonavicular joint surface.
Laterally, there is no bone loss and the fracture is stable through interdigitation, allowing it to withstand compressive stress. The optimal fixation method is a cannulated lag screw. The screw should pass through the bone of the lateral talar neck, not the articular cartilage.
These screws do not need to be placed parallel, as their mechanisms differ: the lateral screw provides compression, while the medial screw serves only for positional fixation.
Completion of Fixation
Intraoperative C-arm checks ensure accurate reduction of all talar joint surfaces. Canale views of the ankle and foot confirm satisfactory reduction and fixation of the talar neck fracture.
The illustration shows stable fixation of a Hawkins type II fracture. Note the non-parallel screw placement: a compression screw laterally and a positional screw medially.
Experienced surgeons sometimes employ a posterior-to-anterior screw fixation technique.
Postoperative Management
● Postoperatively, the foot should be immobilized in a posterior splint in the neutral position. Early mobilization exercises for the ankle and subtalar joints are recommended.
● Weight-bearing is prohibited for 6 weeks postoperatively. Follow-up X-rays are taken at 2 weeks and 6 weeks.
● Joint mobilization exercises should be started as early as the patient tolerates, aiming to restore a good range of motion.
● X-rays at 6 weeks confirm fracture healing. Once bony union is achieved, gradual weight-bearing training can begin.
● Patients with talar neck fractures should not start weight-bearing as long as there is pain at the fracture site.
