One of the problems with using bone prosthesis in children’s legs is that they usually end up with leg length discrepancy and so require numerous surgical interventions over the years to manually lengthen the leg.
Magnetic fields are now being used to lengthen the bone prosthesis and hence avoid the need for surgery and all associated risks and expenses. In a procedure that takes around 20 minutes, an external magnetic field is used the drive a motor to turn a screw and thereby lengthen the leg. See the procedure here …