When children have cancer that invades their bones, they often face multiple surgeries and a lifetime of problems. The fact that the bones in a child are still growing means that tampering with those bones can result in serious problems with limb length and function.
Wright medical has developed a bone replacement device called REPIPHYSIS. The amazing thing about this is that these artificial bones grow as the patient grows.
It works in a simple fashion. A spring is encased in plastic. A special device is placed externally over the implanted device and it creates an electromagnetic field which causes melting of the plastic. As it softens, the spring expands and the leg gets longer.