Dr. Christopher Cannova of Orthobethesda and his patient Christina Starr discuss the parts he used in replacing her knee. (Jeffrey MacMillan/ )

After D.C. resident Christina Starr was hit by a motorcycle in 2009, three surgeons told her not to return to ballet class. After five years of cortisone shots, she started looking into getting a knee replacement, and Bethesda surgeon Chris Cannova offered something she hadn’t heard before — a customized knee replacement made using a 3-D printer.

Two days after the surgery this August, she walked out of the hospital without crutches, and six weeks later, she returned to dance class.

“They told me, ‘We’ve never heard of anybody getting a knee replacement and then going back to any kind of dance activity where you have you have to tilt and spin and pirouette.’” she said.

Cannova and his partner are among the first surgeons in the Washington area using knee implants made with a 3-D printer, and they have used them in hundreds of operations in the past two years. The knee implants, produced by Massachusetts-based Conformis, are put into use by just a few dozen doctors in the Mid-Atlantic area. Since the company first made the technology commercially available in June 2011, the process has been used in more than 10,000 procedures.

The 3-D printers are machines that produce physical objects by spraying ultra-thin layers of material on top of one another. In recent years, the medical industry has been using printers to create a variety of products from artificial heart valves to skin grafts. Some are even experimenting with printing entire organs.

Dr. Cannova is one of the first in the nation to do a knee replacement with an implant made by a 3-D printer. (Jeffrey MacMillan/ )

The medical significance of Cannova’s technique lies in the ability to customize a new knee for each patient. Most surgeons go into a knee surgery with seven possible knee sizes, and pick the one that appears to be the closest fit while the patient is on the surgical table.

Then they chip away at different parts of the bone until the implant fits, potentially leaving the patient with years of discomfort if the size isn’t quite right.

Conformis’s knee replacement uses a CT scan to size up the patient’s knee before the implant is even manufactured. It then prints a wax mold of the implant based on the dimensions of the patient’s knee, which is then used as a model for the implant itself. The imaging software and 3-D printer allow the company to turn around a new knee in about five weeks.

Conformis’s technology was approved by the Federal Drug Administration in February 2011, and doctors occasionally debate whether it is preferable to traditional implants. Tariq Nayfeh, an orthopedic surgeon at Medstar Harbor Hospital in Baltimore, told the Baltimore Sun there is “absolutely nothing to demonstrate that [Conformis’s technique] is better,” arguing it does not justify the added cost of the CT scan.

Cannova says his patients with insurance or Medicaid see little cost increase compared to a traditional implant because most insurance plans will cover the CT scans, which typically cost a few hundred dollars.

“Insurance companies consider this just to be a knee replacement.” Cannova said.

Fort Worth surgeon Bruce Bollinger, who performs custom knee replacements using Conformis’s implants and also served on one of the company’s advisory boards, said his office usually charges between $4,000 and $7,000 for a knee implant, and Conformis’s version sits in the middle at $5,000. The full cost of the operation depends on the hospital and the insurance plan, but in general, a customized Conformis knee costs the same as a traditional implant, Bollinger and Cannova agreed.

Although the customized knees are slightly more expensive to make than a traditional model, Conformis chief executive Philipp Lang said they have made a conscious decision to price them competitively.

But 3-D printing’s greatest mark on the industry could come in its effect on inventories. One of the most difficult challenges facing medical device manufacturers and hospitals is staying stocked enough so that surgeries can be arranged within a reasonable time period. Maintaining a proper inventory is a challenge that can contribute to patient costs.

With 3-D printing, the company can peg production to the number of patients in need.

Conformis “has the best business model that you could ever imagine for an implant company,” Cannova said. “They have no inventory, and the implant is sold before they even create it, because it goes to a particular person.”