Dr. DiStefano from St. Francis hospital in Maryville is performing a total knee replacement, a procedure he's done hundreds of times.
"[I'm] entering my fifteenth year in practice," he tells us.
His patient is Dewayne Leer, a St. Joseph man who says he's battled knee pain for years.
"Over time the pain's come back and it's as bad as it ever was," Leer said.
Dr. DiStefano shows us CT scans of Leer's legs, and of his knee joints.
Each image is a piece of data for a 3D printer.
The printer has made a model of Leer's knees, and the surgeons will use it in the operating room.
The Prophecy, as it's called, is used as a guide for where they do their work during surgery - it will line up the joint replacement in a way specific to Leer's body.
"Everyone's concern is how long is this going to last? We typically tell people somewhere between 10 and 25 years, looking for 20 years," Dr. DiStefano said. "But we feel if we can get the alignment more precise it will only increase that time if it wears more normally."
They've had this technology at St. Francis only for a few months.
Dr. Distefano says he's used it dozens of times now.
But he says two total knee replacements can be done in less than an hour's time.
"To me it's revolutionary," Dr. DiStefano said. "It just makes my job easier, and it also makes the placement better than I could have done it before even with all that experience."
For Leer, that just means he'll be that much closer to being back on his feet.
"I just wait for the day when I can just go out in the evening and just walk around in the neighborhood if I choose to do that, or play around of gold pain free," Leer said. "Whatever I do, I just can't wait to do it."
Dewayne Leer's recovery will be relatively similar to any other knee replacement.
Once he's back on his feet, he will still use a walker to get around for the next few weeks.