KEARNEY — Dr. Chris Wilkinson holds a little box about the size of a shoebox.
Opening the lid, he pulls out the small parts used in knee replacements. They’re custom-made for each patient.
Wilkinson, an orthopedic surgeon at Kearney Regional Medical Center, said he became the first doctor in Nebraska to offer customized knee replacements four years ago.
First, a patient has a CT scan from the hip to the knee and ankle. Based on that, a 3D model is created of the joint. This allows the surgeon to determine how the implant will fit. Wilkinson then discusses the procedure with the patient. If the patient chooses this procedure, the CT scan is sent to Conformis, a Boston company that starts building the implant. It arrives in about five weeks.
“It comes in a box, about the size of a couple of shoeboxes,” he said. The box contains cutting blocks made out of medical grade nylon. The plastic fits on the end of the femur. “These are to prepare the bone for the final implants.”
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A radiologist came up with the concept of applying computer-aided design and computer-aided manufacturing techniques to total knee replacement to make customized joint replacements.
Doctors continue to cement these implants in place, but the new trend is a cement-less procedure, he said.
Wilkinson remains the only orthopedic surgeon here doing the process, although surgeons in Omaha and Lincoln now have begun offering the new procedure.
A generation ago, joint manufacturers theorized that metal joints would last longer. Now, plastic has replaced metal.
Meanwhile, research continues. While 80 percent of patients who get knee replacements are satisfied, 20 percent complain of pain after the surgery.
“We don’t know why,” Wilkinson said. “In the ‘90s, it was found that knees with lesser quality plastic failed within four to six years, while others with the good plastic could last 15 to 20 years, but that problem seems to be much less now.
“We also know if the implant is too big and overhangs the bone, that seems to cause pain. Even hanging over by three millimeters causes problems, so companies began making more sizes of replacement knees.”
The Conformis model allows Wilkinson to create a joint that “fits perfectly,” he said.
An orthopedist for 35 years, Wilkinson said he has seen “no bad results” with this method. It was approved by the Federal Drug Administration in 2011. Eight years “is not a very long time to judge results, but the preliminary research and papers suggest it’s going in the right direction,” he said.
He said he knows an orthopedic surgeon in Las Vegas who has performed 1,000 such surgeries. “He has gone from 20 percent of patients with post-surgical pain to about five percent,” he said. “That is hearsay, but it is encouraging. I think people are doing better with these. Overall, we get more range of motion in the knee, and people think it feels more normal, which is the goal.”
He does about four such surgeries a week, or about 100-120 a year.
One patient, he said, had a “standard” knee replacement on one side and a Conformis on the other. She had 10 degrees more motion on that custom side. “She said, ‘I love both my knees, but I like the custom knee better. It feels more normal,’” he said.