– An ankle joint replaces the knee

If the knee is affected by extensive tumors, sometimes the only option is leg amputation. However, if you don’t mind appearances, you can use your foot as a knee joint.

Author: Vera Stucki

Preserve the functioning knee joint: Whenever possible, that’s the stated goal of surgeons – even if the bone in the knee area is affected by soft tissue or bone tumors. If this is no longer possible, only an amputation at the level of the thigh can save life. For the patient, this means a complete leg prosthesis including a mechanical artificial knee, combined with significant limitations: Running no longer works as before and costs a lot of energy, many sports become impossible. The so-called rotational plastic, or rotational plastic, provides a remedy here.

Reverse Plastic Series

  • (1) An ankle replaces a knee (1) An ankle replaces a knee
  • (2) The time after the amputation (2) The time after the amputation
  • (3) Learning to walk again with foot on knee (3) Learning to walk again with foot on knee
  • (4) Everyday patience test (4) Everyday patience test

First performed as early as 1927, the principle is as simple as it is ingenious: it uses the ankle joint of the leg that is to be amputated. It is usually not affected by the tumor and can perform the same movements as a knee joint. Instead of amputating the entire leg, the foot including the ankle joint is obtained and attached to the thigh in such a way that the ankle joint is at the level of the former knee joint – rotated by 180 degrees so that it can be bent backwards like a knee.

Now all that is needed is a lower leg prosthesis to be placed on the sole of the foot. Because the main nerve of the leg is preserved in its course to the ankle, the foot remains sensitive and mobile. Another big advantage is that because the nerve is not cut, there is no phantom pain. The blood vessels are also preserved as far as possible.

Meticulous precision work

The operation itself demands a lot from the surgical team. First, it must neatly expose the main branch of the leg nerves, leg vein and leg artery from the tissue, interrupting all the secondary branches one by one. In most cases, dozens of vessels go into the tumor; they all have to be detached so that no tumor tissue adheres to the remaining part of the vessel. If the tumor has affected the main trunk of the vessels, the affected part has to be removed and the interfaces have to be sutured together by fine surgery.

Then the "rough work" begins: the surgeons cut through bone and muscle and remove the tumor-affected leg section. The femur and tibia are now processed so that they can be screwed together with a plate.

Then the muscles are sewn together: always the muscles of the thigh with the originally opposite muscle of the lower leg, which now takes on the opposite function. When closing the wound, there is still a problem to solve: The circumference of the femoral stump is significantly larger than that of the lower leg. That is why the skin of the upper leg is interlocked with that of the lower leg.

Deterrent body image

For the patient, the operation is by no means the end of the story. Only after a few weeks have the wounds healed enough for him to be able to put on a lower leg prosthesis for the first time. Afterwards, he has to learn how to stand and walk completely new, because the changed constellation of muscles and nerves requires different movement sequences. After one to two years of physiotherapy, however, all activities are usually possible – including most sports activities.

The only disadvantage is the strange appearance, which has to be coped with. This is also a major reason why reversal plastic surgery is rarely performed: Many patients prefer to live with a completely amputated leg rather than a foot on the knee, and therefore choose not to have the surgery.

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