What Is a Trimalleolar Fracture?

A trimalleolar fracture is a type of broken ankle. On the inside of the ankle, the lower end of the shin bone, or tibia, forms a knob of bone called the medial malleolus. A thinner bone known as the fibula runs down the outside of the lower leg and at the end it forms a bump called the lateral malleolus. The posterior malleolus, or third malleolus, is formed by a lip of bone at the rear of the lower end of the tibia. When an ankle fracture involves all three malleoli, it is known as a trimalleolar fracture, and surgery is usually required to fix the broken bones together while healing takes place.

Ankle fractures, including a trimalleolar fracture, may be caused by falling or suddenly twisting or turning the ankle. They may also occur as the result of a car accident, together with other lower leg injuries. As a number of different bones make up the ankle joint, the severity of a broken ankle can range from a crack in one bone to breaks in several bones, sometimes piercing the skin. Symptoms of pain, swelling, bruising, and deformity may develop and the ankle may not bear weight.

If these symptoms are noticed when examining potentially broken ankle bones, fractures may be suspected. X-rays may then be taken to provide an accurate diagnosis. In some cases, only the medial or the lateral malleolus may be broken. If the bones are not too far out of place and the fracture is considered to be stable, meaning it will stay put when the bones are realigned, surgery may not be necessary and treatment may consist of a cast or splint. In the case of a trimalleolar fracture, or a bimalleolar fracture, where the medial and lateral malleoli are broken, the injury is typically unstable and surgery is usually necessary.

The surgical treatment of a trimalleolar fracture generally involves using a combination of metal plates and screws or wires to hold the broken bones in alignment while healing occurs. It is not possible for the ankle to bear weight until the broken bones have fused solidly together, and this can take up to four months. X-rays may be taken during this period to check that the bones have not moved out of place. As soon as it is possible to move the ankle, a program of exercises may be recommended to strengthen the muscles around the joint.