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Candidate:
This radiograph displays a lateral view of the left ankle, where a displaced talar neck fracture is evident. It shows a clear dislocation of the subtalar joint, while the tibiotalar and talonavicular joints remain congruent. Based on these observations, this injury can be classified as a Hawkins type II fracture.
Candidate:
The Hawkins classification is a system used to categorize fractures of the talar neck. This classification is crucial because it helps predict the subsequent risk of developing avascular necrosis or AVN, based on the severity of the injury.
Type I is an undisplaced neck fracture, carrying a 10% risk of AVN. Type II, as in this case, is a displaced neck fracture with subluxation or dislocation of the subtalar joint, having a risk of AVN ranging from 30-60%.
Type III represents a displaced neck fracture with subluxation or dislocation of both subtalar and tibiotalar joints, increasing the risk of AVN to between 60–90%. Lastly, Type IV is the most severe, with displaced neck fracture and subluxation or dislocation of the subtalar, tibiotalar, and talonavicular joints, carrying up to 100% risk of AVN.
Candidate:
Yes, this type of injury is typically caused by an axial load applied to a dorsiflexed foot. A common scenario involves a road traffic accident where the force exerted by the pedal drives the talar neck against the anterior tibia plafond.
Candidate:
This type of injury is high-energy, thus it requires immediate assessment and resuscitation following the Advanced Trauma Life Support (ATLS) guidelines in an emergency department. I would first check the neurovascular status of the limb and conduct a circumferential examination of the skin to look for any signs of an open fracture. Pain management is essential, so I would ensure the patient receives adequate analgesia. I’d also place the patient’s ankle in a below-knee backslab for temporary stabilization and immobilization prior to obtaining a CT scan for a more detailed assessment of the fracture.
Candidate:
The definitive management of this displaced talar neck fracture would involve open reduction and internal fixation. This would be achieved through an anterolateral incision, and possibly an additional anteromedial incision, depending on the complexity of the fracture.
The goal is to achieve a ‘cortical key’ for reduction, while minimizing damage to the blood supply, particularly the deltoid branch of the posterior tibial artery. Once the fracture has been adequately reduced, it would be temporarily fixed with K-wires before applying definitive fixation with two cannulated, partially threaded, cancellous screws.
Candidate:
As with any surgical intervention, there are risks of early and late complications. Early complications include wound dehiscence and infection, especially with open fractures. There’s also a risk of compartment syndrome due to the high-energy nature of the injury.
Late complications include avascular necrosis or AVN, secondary osteoarthritis, delayed union, mal-union, and non-union. A mal-union can often result in a varus deformity of the hindfoot. This happens due to compression of the comminuted medial portion and the subsequent loss of length of the medial column of the foot.
Candidate:
Yes, the talus has a complex blood supply derived from three main arteries. Firstly, the posterior tibial artery gives rise to the artery of the tarsal canal which is the main supply to the body of the talus, and the deltoid branch, which in a displaced neck fracture may be the only remaining supply. Secondly, the dorsalis pedis artery supplies the talar head and neck. Lastly, the peroneal artery gives rise to the artery of the tarsal sinus.
Candidate:
The Hawkins sign is a radiographic indicator of vascular integrity of the talus following a fracture. It is characterized by the presence of a subchondral lucency in the talar dome, best seen at the superior aspect of the talar body on an AP radiograph. This lucency, or decreased subchondral bone density, usually appears approximately 2 months following the injury.
The Hawkins sign is significant because its presence indicates that there is sufficient vascular supply to the bone to allow normal disuse osteopenia, due to subchondral resorption, to occur. In other words, it’s a positive sign suggesting a lower risk of avascular necrosis, as it indicates that the blood supply to the talus has been maintained despite the fracture.
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