Wednesday, December 10, 2003

Device lets surgeons navigate the knee

By Tim Bonfield
The Cincinnati Enquirer

[IMAGE] Dr. Michael Swank (right) demonstrates how new technology is used to allow for more accurate knee replacement surgery. At left is physician assistant Jon Grote
(Brandi Stafford photo)
Delhi Township resident Ed Busken didn't need to understand all the science involved to understand the value of the computer navigation system used during his knee replacement surgery at Jewish Hospital in Kenwood.

"I was on my feet in four days. I didn't even need a walker," said the 72-year-old retired office equipment repairman. "A lot of my friends have needed knee replacements. Some of them went through twice as much rehab as I did."

Nearly two years ago, orthopedic surgeon Dr. Michael Swank became the first in the U.S. to perform a knee replacement operation using the Vector Vision guidance system made by BrainLAB, a company based in Munich, Germany.

Since then, Swank has performed more than 160 similar operations, including the one on Busken's left knee. He has helped train other surgeons from across the United States, lectured in several cities, and presented data this year at the International Society for Computer Assisted Orthopaedic Surgery.

And while Swank remains the only doctor in Cincinnati doing the procedure, he won't be for long.

At least one, possibly four, area hospitals are considering spending $70,000 to about $160,000 each to buy upgraded versions of the BrainLAB system. Several other companies, including Medtronic, GE Medical Systems and Stryker Corp., have developed or are developing competing products for knee replacements and other forms of orthopedic surgery.

"Think of it as a global positioning system for the human body," Swank said. "GPS revolutionized the aerospace industry. Computer assisted navigation technology is going to revolutionize the process of surgery in much the same way."

More than 250,000 people a year in the United States get knee replacements to correct years of worsening pain from walking around on damaged knees. Often the surgery is needed because the meniscus - a doughnut shaped piece of shock-absorbing cartilage - was torn and removed years ago after a sports injury, or it has gradually worn out because of age, misaligned legs or other conditions.

Without the meniscus, the bones of the knee grind together, triggering painful arthritis. Once the condition gets bad enough, surgeons replace damaged bone with metal and plastic parts.

Much like balancing a tire to avoid uneven tread wear - only much more complicated to do - proper positioning of the replacement parts is crucial for a long-lasting, pain-free knee replacement.

The current gold standard for keeping a patient's leg in precise alignment during the operation involves placing metal rods up to 2 feet long each into thigh and shin bones. Those rods are connected to metal jigs near the knee joint to keep the leg from shifting while cutting bone and attaching replacement parts.

Under the new method, those long rods aren't needed, which allows the surgeons to make smaller cuts through muscle and tendon to reach the bone. That reduces the pain and time spent in rehabilitation, and may also reduce the risk of bone infections, Swank said.

Instead of the long rods, the surgical team connects Y-shaped tracking rods to the metal jigs that stay outside the bone. The tracking rods sport marble-sized balls that can be easily spotted by a computer camera system.

Once the cameras record the original, ideal position established by the surgeon, the computer system can alert the doctors to unwanted shifts. The system also allows doctors to track how the knee joint reacts when ligaments are artificially tensed during surgery. Such "soft tissue balancing" wasn't possible before, Swank said.

In most cases, the operation takes a few minutes longer than the standard procedure. But with more precise positioning during the operation, doctors predict that knee replacements will last longer - which could reduce the need for second operations.

BrainLAB officials say doctors are more likely to be interested in the latest version, because it no longer requires sending patients to get CT scans.

Swank became interested in the project as he already was familiar with computer navigation systems being used in spinal surgery and was interested in applying the concept to joint replacements.

Busken wasn't seeking to be involved in an unusual type of surgery. He visited Swank because the surgeon was recommended by a chiropractor Busken had visited because his knee pain was making it harder to get up and down steps.

Once Swank explained the procedure - and knowing what some of his friends had experienced - it was easy to agree.

Attendance is growing sharply at medical conferences explaining the emerging systems.

"The technology is still in evolution. There are early adapters and other people who are waiting for it to make prime-time," Swank said.


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