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Computers Help Surgeons Custom-Build New Knees by Dr. Deveney

News-Times Archives - This past summer, when Geraldine Powell disembarked from her kayak, she did not step lightly onto the land. "I sort of rolled out," she said. Powell, 58, of New Milford, is an active woman — a swimmer, diver, golfer, kayaker, and skier who teaches at Mohawk Mountain in Cornwall. But this year, one of her knees went south in a hurry. Despite several small operations, it became so painful from arthritis that she couldn't do much of anything that involved moving her legs.

"I was bent over when I walked," Powell said. "I couldn't bear the pain."
Today, she is at Bethel Health Care recovering from knee replacement surgery. The physical therapists there push her, she said. She's progressed from using a walker, to using a cane, to walking unaided. By winter she plans to be back on the slopes.

"It's going wonderfully," she said. "There was no bruising or swelling."

In ordinary circumstances, knee replacements work. There are now about 500,000 total knee replacement surgeries performed in the U.S. per year and about 90 percent of patients regain normal function.

"It's one of the best operations we have to offer for pain," said Dr. Robert Deveney, co-director of the joint replacement program at Danbury Hospital.

But Deveney and Dr. Ronald Tietjen -- chief of the hospital's Center for Advanced Orthopedics -- have now found a way to make this good
thing better. It may be one of the reasons Powell is recovering so quickly and with so little pain.
What they are now offering patients — both at the hospital and at their private practice, Danbury Orthopedics Association — is custom-fit knee replacements. The hospital was the first facility in the state to offer the procedure.
Using MRI imagery and a special computer program, doctors are now able to get a three-dimensional picture of what a knee joint looked like before arthritis set in — before cartilage wore away, before muscles and ligaments stretched and bone spurs grew.

They are then able to plan the surgery out in advance, selecting exactly the right size artificial parts and reducing the amount of bone they have to remove.

"I saw this a couple of years ago," Tietjen said. "I immediately thought this is where knee replacements are going. It's a quantum leap forward."

"We need to do more study on this," Deveney said. "But anecdotally, our patients seem to be recovering more quickly because of it."
Knees are made up of the ball of bone at the end of the thighbone — the femur — that fits onto the top of the shin bone — the tibia. Both are lined with cartilage, the hard, smooth tissue that allows two ends of a joint to move against each other with ease. There is also cartilage lining the back of the patella, or kneecap; synovial fluid helps lubricate the joint.

The body doesn't regenerate cartilage, so it can lose its ability to absorb shocks over time. When cartilage is torn or damaged in an injury, or when it just wears away over the years, bone painfully rubs on bone. That's called osteoarthritis.
"Cartilage is like the rubber on your tires," Deveney said. "It wears out."

Orthopedists can delay major knee surgery for years by prescribing pain-killing drugs and injecting artificial synovial fluid into the knee. But Deveney said osteoarthritis is a degenerative process and eventually doctors have to consider knee replacements.
He said one misconception of the surgery is that surgeons replace the entire joint. "We're actually only putting a new surface on the bone," Deveney pointed out.

That surface can be made of high-tech metals, ceramics or high-density plastics. Artificial joints have improved so much and last so much longer that surgeons are now doing knee replacements on people in their 50s, and even 40s, rather than waiting another decade or so.
The surgery has its complications. Because human knees come in different sizes, doctors have to take X-rays of the existing joint to get a proper fit. Age and other factors can alter the replacement parts.

"If a person is relatively young and active, we might choose one style of knee," Tietjen said. "If patients are 90 years old, we might choose something that allows them to get back in circulation more quickly."
During the operation, surgeons have to fit the new surfaces onto the old bone while trying to find a balance that will allow the joint to move naturally.

"You have to get all the ligaments in balance, all the tissue in balance," Tietjen said.