Magnetically-Controlled Growing Rods

MAGEC (Part 2)

In the last posting the MAGEC system for Early Onset Scoliosis
was introduced.  This system is a
significant improvement when compared to Traditional Growing Rods, mainly due
to the ability to lengthen the instrumentation without the need for anesthesia
or a trip to the operating room.  The
benefits of this device are easy to see, but was with any new technology there
are some drawbacks or limitations.  The
MAGEC device is a cutting-edge, high-tech magnetic lengthener and complicated
devices may not function as intended.
The MAGEC device requires a magnetic field from the ERC (shown below) to
spin the magnets in the implanted actuator.
It is possible the distance between skin and the actuator is
too great, making the magnetic field too weak to lengthen the actuator

 This can happen, in children with more subcutaneous fat, an
older patient and if the actuator was deeply buried in soft tissues around the
spine.  Personally I have had only one
patient in whom the MAGEC device was unable to be magnetically lengthened.  The remaining 30+ patients in my practice
with this device have been easy to lengthen.

The other problem with the MAGEC device was in breakage of
the actuator pin.  If this happens the
actuator will not lengthen with the ERC.
Several reports of actuator pin breakage have surfaced, with most of
them being from Asia and Europe.  This is
because the MAGEC system was first released overseas so there is a slightly
longer experience with this device outside of the U.S.  This was also the first-generation of the
MAGEC device.  When the MAGEC device was
released in the U.S. the actuator pin design had been improved, creating a
second-generation.  This is what we
currently use in the U.S.  I have not
seen any actuator pin breakage yet in my patient population. 
Another mode of failure of the MAGEC device is rod breakage,
either above or below the actuator.  This
type of failure is the same as what is seen in Traditional Growing Rods.  The metal rods are constantly stressed, or
cycled, by the child on a daily basis.
These stresses are cumulative on the rods and will gradually weaken
until there is a fracture or breakage of the rod. 
This problem can be partially avoided by using the larger
sizes of the MAGEC rods, specifically the 5.5 mm rods instead of 4.5 mm
rods.  However, due to patient size we
cannot use 5.5 mm rods as the patient is just too small to hide the rods in
their back without breaking through the skin or being painful.

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