Boston Doctors Fit Custom Knee Replacements

By Toni Waterman

Aug. 1, 2011

BOSTON — For Julie Fitzgerald, a simple stroll around the block always leads to the same place.
“Oh, I think I need a seat,” she says as she walks through her font door.
She lands on her couch, propped up by pillows, left knee buried under an icepack. Fitzgerald was once an avid runner, but she says a simple gardening injury 10 years ago has left her nearly incapacitated. 
“Everything I did I would have to stop and think. Where did I have to walk? What would I do when I got there? Would I be able to get ice? Would there be a place to sit?” Fitzgerald said.

The iDuo G2 is the second-generation knee replacement made by ConforMIS, a Burlington-based company. Using CT imaging ConforMIS makes a 3D model of the bones in a patient's knee and then designs and manufactures a custom replacement such as the one seen above.

Photo from ConforMIS via Flickr

She knew she’d reached her breaking point when she couldn’t even sleep at night. She says she’d fall asleep, but not for long.
“A lot of tossing and turning, an awful lot of tossing and turning so the sleep pattern would be broken up by doing that, too tired to get up and get more ice,” she said. “You’d think 12 puppies slept in my bed by the time I got up in the morning if you looked at the blankets.”
Frustrated and in pain she turned to Dr. Wolfgang Fitz at Brigham and Women’s Hospital. His prescription was a new procedure called a custom total knee replacement, in which each patient gets a knee implant designed just for them.
“It’s really the first time we are able to reconstruct the surfaces of each patient individually,” Fitz said.
Since the 1970s, doctors have replaced knees with generic new ones. On surgery day, they’ll grab the closest fit off the shelf and then whittle down the knee and the patient's bones until they fit together. But Dr. Fitz says that, try as he might, it’s never been perfect.
“In the past, we had patients where the implant over hanged or under hanged. And we know from studies that just a couple of millimeters of overhang causes more pain,” Fitz said.
He says pain is one of the problems with total knee replacements and that 10 percent of knee recipients still have pain a year after surgery.
But now, Burlington-based ConforMIS is using 3D CT scans and a special computer program to create customized implants in just six weeks. Once ConforMIS gets the data, their engineers digitally separate the bones in 3D and then create a model of each person’s knee. Using that information, ConforMIS can then manufacture a patient-specific knee.
Fitzgerald went in for her custom replacement in May, and two months later, says she’s “ecstatic” at where she is in her recovery.
“When I went to outpatient physical therapy, they were actually surprised that I had my surgery as recently as I had…they thought that the range of motion I had was a little bit more than they had seen with the traditional (knee replacement surgery),” Fitzgerald said.
Dr. Fitz has done 15 custom knee replacements since May, and says he’s already seeing marked differences. 
“What I’m seeing is less blood loss. I’m seeing that implants and the instrumentations just fit and it’s actually fun to put on because it fits just like a glove,” Fitz said. 
He says it’s too early to know exactly what the overall advantage of the custom knee replacement will be. But for Julie Fitzgerald, that doesn’t matter. She’s just looking to get her life back.
“I’m not expecting 100%, but I’m expecting as close to 90% and that will be perfect for me. But it will be more changing my mind about, instead of saying no I can’t do something, it think that’s what’s going to be interesting. I’ll find myself saying ‘yes’ again,” Fitz said.

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