Rare bone sarcomas often take limb or life, around 3000 in the US every year---mostly in kids. Doctors at Ohio State University Medical Center have successfully used an experiemental bone device called Repiphysis. The cancerous bone is surgically removed and replaced by an artificial bone. As kidsgrow (here's the neat part) the bone can be expanded using heat and magnets from the outside (watch the video, click on picture). The child gets to keep the limb and live happy.
More at the company's site