What is Triplane Ankle Fracture?
Fractures to the growth plate, or the part of the bone that’s still developing, are common in children and teens. These fractures often happen because the growth plate is the weakest part of the bone, making it more prone to injury. One particular type of these fractures, known as a “triplane” ankle fracture, is quite complicated.
A triplane fracture is a specific fracture that involves three parts of the bone: the metaphysis, or main part of the bone; the physis, or growth plate; and the epiphysis, or end of the bone. It’s known as a “triplane” fracture because it presents three different orientations of fracture lines in the lower bone of the leg, or tibia.
This means that the end of the bone is broken in a front-to-back direction and you can see it on a front-to-back X-ray. Then, the back part of the main bone is broken in a side-to-side direction, which can be seen on a side-view X-ray. Lastly, the growth plate is separated horizontally.
The way to treat a triplane fracture depends on how much the bone fragments have moved and if there’s a misstep in the joint. Sometimes it can be treated by just moving the bone fragments back into place without surgery, or sometimes it requires surgical intervention.
The good news is that if a triplane ankle fracture is identified and treated properly, the prognosis is typically excellent.
What Causes Triplane Ankle Fracture?
Triplane ankle fractures are injuries that happen due to a trauma to the ankle in teenagers, often during a time when their growth plates are partially closing. These are similar to Tillaux fractures, another type of ankle injury. They usually occur because of a twisting force applied to the foot while it is pointed outwards.
Most commonly, these fractures happen on the outer side of the ankle, as this is where the weakest part of growth plate is located. It’s also where a strong ligament called the anterior inferior tibiofibular ligament attaches to the ankle.
The less common triplane fractures happen on the inner side of the ankle. These atypical injuries occur due to a forceful inward movement.
Risk Factors and Frequency for Triplane Ankle Fracture
Ankle injuries in kids are very common. In fact, they are second only to hand and wrist injuries in children aged between 10 to 15. Ankle fractures happen mostly in boys and make up 5% of all bone fractures in children. They also account for 9% to 18% of growth-plate injuries.
- Ankle injuries are common in kids, especially aged 10 to 15.
- These injuries are more frequent in boys.
- Ankle fractures represent 5% of all bone fractures in kids.
- They account for 9% to 18% of injuries to the growth-plate where the bone grows.
A specific type of fracture, known as a triplane fracture, makes up 5% to 15% of all kids’ ankle fractures. These typically occur in teenagers, most commonly around the age of 13 years and 5 months, but can happen to anyone aged 10 to 17. Another type of fracture, known as a Tillaux fracture, is usually seen in older teenagers as their growth-plate is more closed off.
- Triplane fractures make up 5% to 15% of kids’ ankle fractures. They usually occur in teenagers, most commonly around 13 and a half, but can happen to anyone aged 10 to 17.
- Tillaux fractures usually happen to older teenagers, as their growth-plate is more closed off.
Signs and Symptoms of Triplane Ankle Fracture
When teenagers hurt their ankles, it’s usually because of a twisting injury that often happens during sports activities. This results in pain in the ankle and difficulty putting weight on it. The most common way this happens is by twisting the ankle outward while the foot is bent inward. There’s also a less common type of injury, called a medial triplane fracture, which happens when a force pushes the foot inward. The injured ankle might be swollen or bruised, and in serious cases, it may look bent out of shape. People usually don’t experience a feeling of a very unstable ankle. However, touching the ankle around its growth plate will be painful. Like with any ankle injury, the doctor should check for any nerve damage or issues with the blood supply and document the findings.
Testing for Triplane Ankle Fracture
Triplane ankle fractures can be hard to identify with standard X-rays because each image generally only shows a single fracture line. Three different X-ray views are important. The first view (called an AP view) shows the fracture line that cuts through the end of the bone (known as a Salter-Harris III fracture). The second view (the lateral view) shows the fracture line in the back part of the bone (a Salter-Harris II fracture). The third view (the mortise radiograph) is the best way to see if the joints of the bones have been moved out of place.
To better understand the fracture, a computed tomography (CT) scan can be helpful. This type of scan can show the exact pattern of the fracture, how much the bones have moved out of place, and if there’s any unevenness where the bones meet at the joint. In fact, one study showed that all surgeons changed how they planned to treat the fracture after seeing the CT scan instead of just based on the X-rays.
It’s important to note that there’s a rare type of triplane fracture that’s different because the main break in the bone happens in a different direction and the injury to the end of the bone is located more toward the inside and is oriented differently.
Treatment Options for Triplane Ankle Fracture
The treatment for a specific type of ankle fracture, known as a triplane fracture, depends on the extent of the fracture and how far the broken pieces have moved from their original position. This is usually determined by looking at CT scan results.
If the fracture is not too severe and the broken pieces are not too far apart (less than 2 mm), a long leg cast can effectively treat the injury. The positioning of the ankle and the success of the treatment is normally checked with a follow-up CT scan. It’s been found that this type of treatment provides excellent results for minor fractures. However, major fractures that are not treated properly can lead to chronic pain and ankle degradation.
For fractures where the broken pieces have moved more than 2 mm, or in cases where non-surgical treatment hasn’t been successful, surgery is typically recommended. The fixation is usually achieved with one or two screws, aligned parallel to the growth plate of the bone. The screws can be inserted in different parts of the bone, depending on the nature of the fracture. There’s no proven superiority of using one type of screw over another type in the treatment of this kind of fracture. It’s important that the broken surfaces of the bone are readjusted correctly to ensure the best outcome. Special care is taken to align the screws as perpendicular as possible to the fracture line to maximize compression and maintain the right positioning. Various techniques have been used with wide success, including both closed reduction (realigning the bone without surgery) and open reduction (surgery to realign the bone).
Some medical professionals prefer to use minimally invasive techniques, making small incisions and inserting one or two standard 3.5 mm screws to keep the bone in place. Depending on the part of the bone that is fractured, the screws are placed in different orientations. It’s crucial to make sure all the screw threads are past the fracture, especially if partially threaded screws are used.
What else can Triplane Ankle Fracture be?
When a teenager experiences ankle pain, several medical conditions might be the cause. These possibilities include:
- Ankle sprain
- Tillaux fracture (a specific type of ankle fracture)
- Triplane fracture (a fracture that involves three parts of the ankle)
- Syndesmosis injury (injury to the tissue that connects the two bones of the lower leg)
- Ankle dislocation
- Subtalar dislocation (displacement of the joint below the ankle)
- Fracture of the calcaneus (heel bone)
- Fracture of the talus (bone in the foot)
- Malignancy (cancer)
- Infection
What to expect with Triplane Ankle Fracture
Triplane ankle fractures, when identified and treated properly, tend to have very positive outcomes. There’s a chance, between 7% to 21%, that these fractures may cause damage to the growth plate (also known as the “physis”), or cause it to close too early. The growth plate is the area of growing tissue near the end of the long bones in children and adolescents.
Some people have questioned how important it is to preserve the growth plate, considering the limited potential for growth left. However, it’s still important for doctors to keep a close eye on patients who have over two years left to grow.
A study by Cooperman and others noted three instances of growth problems out of 14 triplane ankle fractures. These all happened in patients who still had over two years of growth left.
Possible Complications When Diagnosed with Triplane Ankle Fracture
There can be some complications during non-surgical treatment, such as the loss of reduction that needs surgical fixing, the bones not joining properly, or persistent pain. Rare issues may occur during the surgical procedure, including bleeding, infection, bones not joining, painful hardware, and temporary nerve damage.
Common Complications:
- Loss of reduction requiring surgical fixing
- Bones not joining properly (nonunion/malunion)
- Persistent pain
- Bleeding during surgical procedure
- Infection from surgical procedure
- Painful hardware from surgery
- Temporary nerve damage (transient neuropathy)
Preventing Triplane Ankle Fracture
Doctors shouldn’t automatically assume a child’s ankle injury is just a strained ligament. The ligaments that keep the ankle stable are actually stronger than the growth plate (the part of the bone that allows growth), making it much more likely for the growth plate to fracture. This is particularly relevant for children of certain age groups.
When doctors are examining X-rays of patients who seem to have a certain kind of fracture in the lower large bone of the leg (known as Salter-Harris II or III fractures), they should be very careful. This is because they might miss an important injury known as a Salter-Harris IV triplane ankle fracture, which could be more serious. Basically, the doctor is using different angles of X-rays to ensure they get a clear and full picture of the injury.