Sometimes arthritis gets so bad the joint has to be fused so it doesn't move any more. The surgeon takes bone chips from a donor bank or from the patient's own pelvic bone and inserts them in and around the joint. New bone cells fill in forming a solid fusion.
Amputation after fusion occurs in up to 15 percent of all cases of ankle fusion. The reasons for this vary from patient to patient. Sometimes the bone doesn't "take" and the joint doesn't fuse. This is called a nonunion. In other cases bone infection eats away at enough bone that there's a danger of gangrene. Amputation may be the only option to save the leg.
Believe it or not, many patients prefer amputation to the intense pain and suffering they've had with the arthritis. With a prosthetic device, they can walk again pain free. They report their improved quality of life was worth the loss of a foot.