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Peripheral arterial disease is the leading cause of leg amputation in the UK. When the blood supply falls below a certain critical level, there is not enough blood and oxygen reaching the tissues and they begin to die. The key signs of this are continuous pain even at rest, development of ulcers or the non-healing of minor injuries, or dry black shrivelled toes (necrosis). Unchecked, the pain will increase and often requires morphine to ease it, or infection may set in causing fever and systemic illness. Either of these developments is an indication that amputation may be required to save life or quality of life. Investigations such as Duplex scans and angiogram will show whether there is any possibility of improving the circulation.
An amputation can be a lifesaving operation, and many patients will mobilise on prosthetic legs to a good quality of life. The main concerns as far as the surgery is concerned are achieving good healing and preserving the maximum use in the leg. Because the body is very good at preserving blood supply until a very late stage, many patients will present with a small ulcer on the heel or toes but with no way of improving the circulation and they will end up with a major amputation.
There are several types or levels of amputations, the least being removal of one or more toes. This might be for bone infection (osteomyelitis) or where the toe is black but the blood supply to the main part of the foot is sufficient to allow the tissue to heal, perhaps after an angiopasty or bypass operation. Even if all the toes are beyond saving, so long as the heel is preserved with healthy skin, the leg can be used to walk reasonably normally with an amputation through the middle of the foot. Unfortunately, the blood supply to the foot is often not much better than the toes and is not enough to achieve healing.
If the foot cannot be saved, the next level of amputation is through the fleshy part of the calf, below the knee. The muscles are used to create a padded stump that lets you use a prosthetic limb.
In severe cases, or where mobility on a prosthetic leg is never likely, then the preferred level of amputation is through the thigh, again, the muscles are used to cover the bone and produce a padded stump.