GPS-like system helps surgeons align joints

By DAWN SAGARIO
Ames, Ia., 12 oct 2008-- You've heard of travelers using a Global Positioning System to direct them from point A to point B.Now some orthopedic surgeons in Iowa are using technology similar to the tracking systems in cars and ships during joint replacement operations.The technology, called a computer-assisted navigation system, helps doctors more accurately align joint replacements with a patient's own anatomy, physicians said. Doing that could help the joint last longer because there will be less wear and tear.
But because the technology is so new, doctors said, there is no long-term data to support that idea."Studies have not demonstrated beyond a shadow of a doubt that the joint will last longer," said Dr. Peter Buck, an orthopedic surgeon with McFarland Clinic.One concern with the new technology is the added surgery time, which could mean a higher risk of infection and blood clots, one orthopedic surgeon said.Buck and other surgeons stressed that the navigation system is just an additional tool for doctors and doesn't replace the expertise of a skilled surgeon.
Wellmark Blue Cross and Blue Shield, Iowa's largest health insurer, does not cover use of the system because it is still considered investigational, said Wellmark spokesman Kevin Teale.Linda White of Ames had a total knee replacement in her left knee performed by Buck on July 27. White, 69, a longtime patient of Buck's, said she would have gone to him even if he hadn't had the computer-assisted surgery training.But, she added, it was a nice perk.
"I was delighted to know there was an extra help to it or some accuracy greater than humans'," White said.The navigation system uses tracking devices placed in the joint, along with receivers located above the operating table.As the surgeon moves a special "wand" within the joint, infrared trackers calculate its position relative to anatomical landmarks. The process is called "registering." Wireless instruments instantly transfer the information to a computer screen, where a virtual image of the patient's knee appears.
The real-time model gives surgeons the best angles and measurements needed to align the implant with the patient's body."I feel like I'm putting in a knee as best as I can, making my cuts as accurately as I can," said Dr. Tom Dulaney, with Des Moines Orthopaedic Surgeons.Dulaney, who works in Carroll, has done 700 to 800 knee replacements using the navigation system in the last three years.He said that the system does not trim recovery times and that there is no proof that it contributes to improved function.
The cost for the navigation system at Mary Greeley Medical Center in Ames was $200,000 to $225,000, hospital officials said.Buck has performed about 100 knee replacements in the last year at Mary Greeley using the system.White said her left knee once made a crunching sound as bone rubbed against bone. She was taking a lot of pain medication and had even stopped shopping at larger grocery stores because walking hurt her knee."There's less pain now," she said after surgery. "Right away I found it much better to walk, without a walker or cane."
Buck said the technology can be particularly helpful in certain patients, including larger individuals and those with old fractures.Medically frail patients would also benefit, he said, because the navigation system does not require drilling a metal rod into the thigh bone as a guide, as is done in the conventional knee surgery.That can dislodge bone marrow that can travel into the blood vessels and potentially cause a stroke.One drawback to the navigation system is the extra time involved, ranging from six minutes to 15 minutes.
Studies have shown a correlation between longer surgeries during general joint replacement and increased risk for infection and blood clots, said Dr. Craig Mahoney, an orthopedic surgeon with Iowa Orthopaedic Center. Mahoney is co-director of the Center for Joint Replacement Surgery and chairman of the department of orthopedics at Mercy Medical Center.But Mahoney added that no studies are specifically looking at those risks.A colleague of Mahoney, Dr. John Nettrour, said, "I don't think an additional six or seven minutes in a surgical case would be an undue risk." Nettrour has performed about 35 knee replacements at Mercy Medical Center in recent months using the technology; he's done about 300 of them total.
Nettrour said he hopes to use the navigation system in hip replacements in about the next six months.Mahoney, who has not used the system with his patients, is interested in other types of computer-assisted surgery that don't use the "registering" process, which is what adds time to the procedure, he said.