The ankle joint is where the bones of the leg (the tibia and fibula) meet with the bones on the hindfoot (talus) to form a joint that allows the foot to bend up and down. The ankle joint is susceptible to injury and one common type of injury is called an ankle fracture.
When people talk about ankle fractures, they are usually referring to injury to the bones of the tibia and fibula. The ends of these bones, commonly called the medial malleolus (end of the tibia) and lateral malleolus (end of the fibula), are the bony bumps that you feel on the inner and outer side of the ankle.
There are different types of ankle fractures that can occur, and one of the more serious types is called a bimalleolar ankle fracture--an injury to both the inner and the outer side of the ankle. Bimalleolar ankle fractures almost always require surgical treatment.
Bimalleolar Ankle Fractures
When a bimalleolar ankle fracture occurs, there is injury to both the medial malleolus (inner side of the ankle) and the lateral malleolus (outer side of the ankle). Because both sides are injured, the ankle joint becomes unstable. An unstable injury occurs when the fracture disrupts the structural integrity of the ankle (joint). Because the joint is unstable, it is susceptible to damage and early ankle arthritis if left untreated. Therefore, the typical treatment is to surgically repair the fracture to stabilize the ankle joint.
Bimalleloar Equivalent Ankle Fractures
One special subset of these fractures is called a bimalleolar equivalent fracture. This typically occurs when there is a fracture of the lateral malleolus and a ligament injury on the inner side of the ankle (the deltoid ligament). While this particular injury does not involve a bone injury on the inner side of the ankle, the ligament injury that has occurred causes the ankle joint to become unstable, and requires surgical treatment to stabilize the joint.
Bimalleolar equvalent fractures need to be considered any time a lateral malleolus fracture has occurred. If there is pain or swelling on the inner side of the ankle, a bimalleolar ankle fracture may be present. Special x-rays, called stress x-rays, can be performed to look for signs of instability of the ankle joint.
Trimalleolar Ankle Fractures
Another variant of this type of injury is called a trimalleolar ankle fracture. The typical bimalleolar fracture involves bone injury to the inner and outer side of the ankle. People who sustain a trimalleolar ankle fracture also have bone injury at the back of the tibia (posterior malleolus fracture) near the ankle joint. Often this does not change the treatment from that of a bimalleolar ankle fracture. However, if the bone injury in the back of the tibia, called the posterior malleolus, causes instability of the ankle joint, it may need to also be repaired at the time of surgery.
Treatment of Complex Ankle Fractures
Treatment of all of these injuries is similar, and almost always requires surgery. The surgical procedure is performed to repair the bones, most often with metal plates and screws. These implants repair the bones to restore the stability of the ankle joint. It is very important to repair the bones with proper alignment; if not lined up perfectly there is a higher chance of developing early ankle arthritis.
One of the concerns of these complex ankle fractures is that they are usually accompanied by significant ankle swelling. Often this swelling can be serious, and may even cause blisters (called fracture blisters) to form on the skin. Surgery is frequently delayed days or weeks if there is significant swelling. Severe swelling not only makes the surgery more difficult to perform, but can dramatically increase the risk of infection and healing problems after surgery.
As mentioned, infection and wound complications are the most worrisome concerns associated with ankle fracture surgery. Other common complications include stiffness and long-term swelling. Many patients notice swelling after ankle fracture surgery for six months, and may always have some increased swelling. Another concern is that because the bone is directly under the skin, metal plates and screws are sometimes bothersome and require removal. Lastly, even with appropriate care, surgical repair, and proper rehabilitation, ankle arthritis can occur.
Michelson JD "Ankle Fractures Resulting From Rotational Injuries" J Am Acad Orthop Surg November/December 2003; 11:403-412.