Magnetic Device Lengthens Child’s Leg

An investigational expandable endoprosthesis will magnetically lengthen
a 9-year-old’s leg and prevent amputation as part of her
osteosarcoma treatment. The metal implant, which is awaiting
FDA approval in the United States, will avoid the need for five to 10
additional surgeries as she grows.

  Rex Marco
  Rex Marco

Rex Marco, MD, oncologic orthopedic surgeon at the University of Texas
Health Science Center at Houston and at Texas Children’s Hospital,
researched this non-invasive device after its introduction during last
year’s combined meeting of the International Symposium of Limb Salvage and
the Musculoskeletal Tumor Society in Boston. Upon meeting Morgan LaRue and her
parents at the multidisciplinary musculoskeletal oncology clinic at Texas
Children’s Hospital, he presented them with the option of this
groundbreaking procedure — instead of the more common amputation or
standard invasive growing prosthesis — and they accepted.

The Stanmore Implants Extendable Distal Femoral Replacement currently is
available in the United States only under an exemption from the FDA for
“compassionate use.” LaRue’s hometown held a fundraiser and
raised more than $40,000 to help the family with medical expenses, Marco said.

On March 29, Marco replaced the cancerous bone in LaRue’s leg with
the metal implant, and she already has undergone her first lengthening

  Morgan LaRue receives her first leg lengthening procedure on her new metal implant.
  Morgan LaRue receives her first
leg lengthening procedure on her new metal implant.
  Image: Texas Children’s

To lengthen the prosthesis, LaRue placed her leg inside a magnetic tube
for approximately 15 minutes. The magnet causes a screw within the prosthesis
to turn, which in turn causes the prosthesis to grow, Marco told O&P
Business News
. This procedure will be used whenever necessary for her
affected leg to keep pace with her other leg.

The device also allows for shortening, if necessary, by turning the
magnet’s switch in the opposite direction.

“Morgan’s leg can grow at the same pace as her other leg
without the need for multiple open surgical procedures, which in turn decreases
the risks of infection, nerve and blood vessel injury, anesthesia, and also
decreases costs of hospitalizations,” Marco said.

Physicians in the limb salvage community still needs long-term follow up
on patients fitted with the device since its first implantation placed about 8
years ago, but thus far, he said has received a positive response.

“The growing child with a malignant primary bone tumor does not
have many good treatment options,” Marco said. “The non-invasive
expandable prosthesis offers the patient a limb salvage procedure that does not
require multiple operations to lengthen the affected limb, which dramatically
decreases the morbidity associated with these multiple open procedures.”
— by Stephanie Z. Pavlou


A diagnosis of cancer often results in a rapid-fire flood of information
and decisions to be made by care providers, the patient and family. As such
techniques become more common, O&P providers may be consulted to provide
information regarding alternatives, or to provide devices that will function
well in concert with an extendable endoprosthesis.

— Don Cummings, CP
Director of
prosthetics, Texas Scottish Rite Hospital for Children

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