The patented REPIPHYSIS® technology is composed of a compressed spring inside a titanium tube, which is locked inside a polymer tube.  During an expansion procedure, a transmitter ring is placed on the outside of the child's limb.  This generates an electromagnetic field around the prosthesis and causes the titanium tube to heat and unlock from the polymer tube.  The spring is then able to decompress and lengthen, allowing the prosthesis to grow inside the child. When the electromagnetic field is removed, the polymer tube locks the titanium tube and freezes it into place, preventing the spring from expanding. 

Each activation of the electromagnetic field lasts for 20 seconds, followed by fluoroscopic imaging.  Fluoroscopy, an x-ray procedure that shows internal parts of the endoprosthesis, enables the physician to monitor the lengthening.  A child may undergo multiple 20-second activations per expansion procedure.

As the child's growth stops, a GUARDIAN® Limb Salvage System product could be implanted for years of continued success.

REPIPHYSIS® Distal Femur
THE EXPANSION
The transmission ring is placed around the leg of the child at the reference point indicated from the fluoroscopic image.

During the 20 second activation, an electromagnetic field is transmitted to the implant, creating heat in the locking mechanism. 

The heated locking mechanism will soften the polymer tube, which allows the spring and implant to expand.  Multiple activations may be necessary to achieve the desired limb length. 

Patent