Ian McGregor lost his leg to a cancerous tumor. Doctors managed to save his life in a never attempted before 18-hour surgical procedure by removing his calf and attaching it to his arm to keep it alive during the tumor and leg amputation.

They used the calf to fix the huge hole that resulted from the operating. The technique itself isn't new according to surgeon Dr. Mani Ragbir who told the BBC. The procedure isn't the first of its kind either.
We are not aware of anyone having done this particular procedure before. It's not easy for a surgeon to tell a patient that they haven't done this particular procedure before.
When they told Ian about it, he just agreed to it. "It felt like something out of Star Trek," he said.
You can't describe the feeling, you think you're at death's door and then you wake up and think wow, I'm here. It's a wonderful feeling.
Ian suffered a large aggressive tumor from his pelvis into his upper left thigh, and when previous treatments were unsuccessful, the only one left was to amputate his leg. When the amputation would occur at his hip, surgeons struggled to figure out how to close up the resulting hole.

They used his calf muscles to close up the wound and to keep it alive, they connected it to his forearm, while temporarily patching the leg muscle's arteries and veins into the circulatory system in his arm.

The surgeons completed the amputation, then transferred the calf muscle to Ian's lower torso to fill in the hole. The entire procedure was done in a single 18-hour marathon surgery.