The talus is one of the three bones involved in the ankle joint. It is the second most common type of tarsal fracture with an incidence of 0.1 percent to 0.85 percent of all fractures. A talus fracture occurs in about 5-7 of foot injuries. There can be fractures of the talar neck, the lateral process of the talus and the talar head.
The top of the bone is an articular surface that connects with the distal tibia. This is where all the weight is borne. On the medial and lateral sides of the talus, it connects with the distal tibia and distal fibula to form the bony prominences of the ankle on the medial and lateral sides. There are facets that join with the bones of the foot on the most distal part of the talus. It also connects with the calcaneus. This means that sixty percent of the surface of the talus is involved in some sort of joint.
The most common mechanism of injury is a motor vehicle accident or fall with the ankle tipped upwards, causing the talus to absorb the blunt of the blow.Evaluation of Talus Fractures
Patients with a talus fracture usually have ankle pain with decreased and painful range of motion of the ankle and foot. There is diffuse swelling of the back of the foot along with tenderness to palpation of the talus directly. Other fractures of the ankle and foot are commonly seen along with fractures of the talus.
X-rays of the side and front of the ankle should be taken along with specialized views that can better identify the whole talus. The CT scan can also be used to see what the fracture looks like and to see how and where it is displaced. Sometimes an MRI or Technetium bone scan can be used to identify fractures that are not displaced and are hard to see on x-ray or CT scan.Classification of Talus Fractures
Talus fractures can be classified according to their anatomic location. This includes the following fractures:
- Talar neck fractures
- Talar head fractures
- Talar body fractures
- Posterior process fractures
- Lateral process fractures
There is also the Hawkin’s classification system l, which is based on displacement. Type I is non-displaced, while Type II is associated with subtalar subluxation or dislocation and type III is associated with subtalar and ankle dislocation. Type IV is associated with a dislocation or subluxation of the talonavicular joint.Treatment of Talus Fractures
Hawkin’s type I fractures are treated with a short leg cast or boot to last 8-12 weeks. The patient must be non-weight-bearing for 6 weeks of the total 12 week treatment time. For displaced Hawkin’s type II to IV fractures, closed reduction is done immediately followed by open reduction and internal fixation. If reduction is possible and confirmed on CT scan, then a short leg splint is used with fracture fixation saved for later. The operative treatment of this type of fracture involves placing two lag screws or headless screws between the fracture segments to hold the fracture in place. Titanium screws are best used because they can be used in a later MRI examination if there is suspicion of osteonecrosis. Grafting must be used if there is comminution or a lot of bone loss. Doctors can use tiny fragment plates that will keep the talus neck from becoming too short.
Talar body fractures are treated without surgery if they are minimally displaced. If there is displacement, the fracture is treated with open reduction and internal fixation. If there are nonviable comminuted segments, these are removed in surgery. After surgery, a short leg boot or cast is applied for about six weeks.Complications of Talus Fractures
Infection is possible but can be minimized by doing surgery early or waiting until the swelling has gone down. Osteonecrosis is a common complication and is defined by the Hawkin’s type of fracture:
- Hawkin’s type I—0-15 percent
- Hawkin’s type II—20-50 percent
- Hawkin’s type III—50-100 percent
- Hawkin’s type IV—Up to 100 percent
Post traumatic arthritis is common, affecting up to 90 percent of cases. This is because a great portion of the talus involves an articular surface.
Delayed union and nonunion can occur in up to 15 percent of cases. It can be treated by repeating the fixation process. Malunion is common after a talar neck fracture. This results in a painful ambulation after healing. An open fracture represents 15-25 percent of all talus fractures. This needs copious irrigation and debridement to prevent infection. Even so, infection involves up to 40 percent of open fractures.
Skin may slough off and there can be interposition of the long flexor tendons. Foot compartment syndrome is possible but rare in talus fractures. If present, then urgent fasciotomy is necessary to avoid neurovascular compromise.
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