Leg implant saves area 6-year-old from repeat surgeries
Six-year-old Katelynn Drydale's body grows like other girls' her age -- mostly at night, a few centimeters each year.
Except for her right leg.
Every six months or so, it grows one and a half to two centimeters -- about three-quarters of an inch -- in just a few minutes.
The Bonner Springs Elementary first-grader's right knee and about half of her right femur have been replaced with a prosthesis featuring Star Trek-style technology. With the use of electromagnetic pulses, the artificial "bone" can be lengthened, without invasive surgery, to match the growth of her other leg. The prosthesis is known as a Repiphysis implant, and in Katelynn's case it connects to her tibia below the knee and to the upper half of her femur.
In November 2004, Katelynn was diagnosed with osteogenic sarcoma, a rare bone cancer that produces malignant bone growth. Katelynn's orthopedic oncologist, Dr. Howard Rosenthal, director of Mid-America Sarcoma Institute at Menorah Medical Center in Overland Park, estimates 450 U.S. children are diagnosed annually with the disease.
In March 2005, Rosenthal operated on Katelynn to remove malignant bone mass and surrounding tissue.
In the same surgery, he implanted the prosthesis. Rosenthal said without this prosthesis, Katelynn would have had to undergo invasive surgery every six months to implant successively larger prostheses to keep up with the growth of her other leg.
Rosenthal said the other best option for Katelynn would have been a kind of double amputation -- joining her tibia to her femur and rotating her foot 180 degrees -- that would facilitate her using an external prosthesis.
To explain how the prosthesis expansion works, Rosenthal likened it to a toilet paper roll holder, with one tube fitting over another and a spring inside the larger tube.
The compressed spring is embedded in plastic, and within that plastic is a receiver. The receiver, activated by the signal from the electromagnetic "wand," heats up the plastic, freeing the spring to slowly expand, which in turn expands the implant.