Diseases

It is important for the health-care professional to take a history as to how the injury occurred. Appreciating the mechanism helps makes sense of the injury and may help direct treatment. Past medical history and previous ankle injury may provide useful information. The dislocated ankle is often diagnosed clinically by the appearance of the ankle. Physical examination can determine the abnormal relationship of the tibia, fibula, and talus. In addition to the ankle, the health-care professional may also exam the structures of the foot and knee, looking for other potential associated injuries. Because blood vessels and nerves can become stretched and damaged when the ankle dislocates, pulses and sensation in the foot are evaluated. Skin complications are common because as the skin stretches over a bony prominence when the ankle is dislocated, it can lose its blood supply and die. X-ray is the initial diagnostic test used to determine the extent of injury, where the bones are in relation to each other and whether a fracture is present. Once the dislocation is reduced and the bones realigned, another post-reduction X-ray may be done to confirm that realignment is good (bones in normal position). Depending upon the situation, CT or MRI scans might be considered to evaluate damage to the joint surface, to look for occult or hidden fractures, and to assess the ligaments and tendons that surround and stabilize the ankle joint.

A dislocated ankle is an accidental injury and most often cannot be prevented. The risk factors are few:

• Recurrent sprained ankles that cause the joint to be lax
• Weakness of the muscles that surround and support the ankle, especially the peroneal muscle
• Diseases that cause joints to be hypermobile (for example, Ehlers-Danlos syndrome, Marfan syndrome, Down syndrome)

Ankle dislocations do not happen spontaneously but are a result of a trauma. Forces are placed on the ankle that cause the bones to fracture or the ligaments to tear, resulting in the dislocation injury. The ankle is an inherently stable joint and the direction of the dislocation depends upon the position of the foot and where the force arises. Ankle dislocations are more often associated with fractures of the bones that make up the joint. Common causes of dislocations are include falls, motor-vehicle crashes, and sports injuries. The most common type of ankle dislocation is posterior, where the talus moves backward in relation to the tibia. For this to occur, the foot needs to be plantar flexed (the toes are pointing downward) when the injury occurs. The ankle is either forced inward from the outside (inversion) or outward from the inside (eversion), tearing the ligaments and tissues that hold the ankle stable. Anterior dislocations, where the talus is pushed forward, occur when the foot is fixed or dorsiflexed (where the toes are pointed upward). The force from in front of the foot pushes the tibia backward. Lateral dislocations occur when the ankle is twisted, either inverted or everted, but there are always fractures associated with either the medial or lateral malleolus or both. Superior dislocation describes where the talus is jammed upward, into the space between the tibia and fibula, as a result of an axial loading injury. This may be due to landing on one's feet from a fall or from being in a car wreck where the foot is held firm against the brake pedal.

Dislocations are painful, and there is usually obvious deformity of the ankle joint. It may be very difficult or impossible to stand or walk. If the nerves that run across the ankle joint are damaged or inflamed, there can be numbness and tingling of the foot. There is almost immediate swelling of the ankle joint area and ecchymosis (bruising) may occur quickly. Depending upon the mechanism of injury, there can be associated other injuries of the foot, knee, or spine.

The ankle is a hinge joint that connects the lower leg to the foot. The tibia and fibula of the leg come into contact with the talus of the foot, forming the ankle mortise. The majority of the weight bearing in the ankle occurs between the tibia and talus. While the shape of the mortise helps align the ankle joint, the surrounding ligaments are very important in providing stability. Picture of a dislocated ankle A dislocated joint describes the situation where the bones that come together to form a joint no longer maintain that normal relationship. In the ankle, it means that the tibia and talus no longer maintain their normal anatomic relationship. Most commonly, a dislocated ankle is associated with fractures of the distal ends of the tibia and fibula (called the malleolus) in association with damage to the ligaments that help support the ankle joint. Less commonly, isolated ligament injuries can result in the dislocation.

While the goal for every injury is to return the patient to their pre-injury level of function, patients who have dislocated their ankle may not necessarily be able to achieve that goal. When the ankle dislocates, blood supply to the cartilage that lines the bone within the joint may be damaged, eventually leading to arthritis (arthro=joint + it is=inflammation). As well, if the bones do not perfectly align after injury, the risk of arthritis in the future increases. Arthritis of the joint may cause pain and stiffness. Loss of range of motion in the ankle can alter gait, the motion of walking, and subsequently affect other parts of the skeleton including the hips and back.

Once the initial evaluation is complete, the goal of emergency treatment of an ankle dislocation begins with trying to reduce the injury, returning the bones as close as possible to their normal anatomic position. Often the bones will fall back into place with gentle traction. Sometimes medication is required to sedate the patient and help the surrounding muscles relax. If there is evidence that the blood and nerve supply to the foot are in jeopardy or if the skin is tented and stretched and the clinical diagnosis of ankle dislocation is made, attempts to reduce the ankle joint may be necessary even before an X-ray is taken to preserve nerve and blood vessel function. Once the ankle is reduced, examination of the blood and nerve supply to the foot is repeated and a temporary plaster or fiberglass splint is placed. An orthopedic or podiatric consultation may need to occur emergently, especially if there are unstable fractures present, if nerve or artery damage exists, or if the ankle cannot be reduced and an emergency operation is needed. Even if the ankle dislocation is reduced, many times an operation is eventually required to stabilize the structures that were damaged. The decision as to whether surgery is required and what type of surgery might be needed is individualized for each patient and their situation. After the initial treatment is complete, whether or not surgery is required, rehabilitation may take six to 12 weeks before returning the patient to their pre-injury activities.