Anatomy
The ankle joint is made up of three bones: the lower end of the tibia (shinbone), the fibula (the small bone of the lower leg), and the talus, the bone that fits into the socket formed by the tibia and fibula. The talus sits on top of the calcaneus (the heel bone). The talus moves mainly in one direction. It works like a hinge to allow your foot to move up and down.
Ligaments on both sides of the ankle joint help hold the bones together. Many tendons cross the ankle to move the ankle and the toes. (Ligaments connect bone to bone, while tendons connect muscle to bone.) The large Achilles tendon at the back of the ankle is the most powerful tendon in the foot. It connects the calf muscles to the heel bone and gives the foot the power for walking, running, and jumping.
Inside the joint, the bones are covered with a slick material called articular cartilage. Articular cartilage is the material that allows the bones to move smoothly against one another in the joints of the body. The cartilage lining is about one-quarter of an inch thick in most joints that carry body weight, such as the ankle, hip, or knee. It is soft enough to allow for shock absorption but tough enough to last a lifetime, as long as it is not injured.
Introduction
Surgery to replace the ankle joint with an artificial joint (called ankle arthroplasty) is becoming more common. Recent advances in the design of the artificial ankle and changes in the way the operation is performed have made artificial ankle replacement a growing alternative to ankle fusion for the treatment of ankle arthritis. The restoration of range of motion is the key feature in favor of ankle replacement with respect to arthrodesis. There is another very important aspect to ankle replacement in that it avoids the stresses that occur following ankle fusion or arthrodesis. When an ankle joint is fused, there is of course no up and down movement in the ankle. There does however remain for some patients a limited amount of up and down movement which occur in the adjacent joints.
Indications :The ideal patient, is someone who is over the age of 50, is not too heavy, and is not extremely active