Verasense brings balance to knee replacements

Consider these facts taken from a recent National Center for Health Statistics report: In 2010, total knee replacement was the most frequently performed inpatient procedure on adults aged 45 and over. From 2000 through 2010, an estimated 5.2 million total knee replacements were performed, with the rate of procedures for both men and women nearly doubling over that period.

And when it comes to gauging a successful knee replacement, it’s all about patient satisfaction. Dr. Brian Blackwood is an orthopedic surgeon with Boulder Community Health, specializing in knee and hip replacements. “There is a component of knee replacement patients where the X-rays look good but they still aren’t really happy with their knee,” he said. “Traditionally patients who are satisfied or very satisfied with their knee replacement are around 80 or 85 percent, so 15 to 20 percent of the patients just aren’t happy with the performance of their knee.”

Now technology is helping to improve those numbers by way of a system called Versasense.

In a total knee replacement, caps are installed on the end of the femur and the tibia. Between those caps, a durable plastic implant is inserted that takes the place of the original cartilage. And getting those parts to mesh properly is the tricky part, Blackwood said. “One of the most difficult things you can do as you go through training is gain an appreciation for what a well-balanced knee replacement feels like.”

In the past, that was done mostly through touch, a somewhat subjective process passed on from more experienced surgeons.

“Now [with Verasense] we actually get objective numbers,” Blackwood explained. “We get feedback on whether one side is too tight or too loose compared to the other side.”

That feedback comes from sensors embedded in flexible “smart trials,” plastic inserts that are the same shape and size as the final implant. When in place, the sensors sit on either side of the joint and send pressure readings to a computer. “We can take the joint through a range of motions and find out what the pressure is,” according to Blackwood, “following the tracking of the joint from full extension to deep bending so you can make sure there’s good balance of the knee throughout that entire range of motion.”

Based on those pressure readings, the surgeon can make adjustments to the surrounding soft tissue or change bone cuts in order to achieve optimal balance for the final implant.

“It’s like a tire — you want to make sure it’s well-balanced so that it won’t have any excessive wear on one side or the other,” he said.

At age 64, Boulder resident Paul Fuller still leads an active life, listing trail running, ultra-running, and nordic and alpine ski racing among his hobbies. Fuller recently had his left knee replaced by Blackwood. “I’m psyched that it’s worked as well as it has. I can do anything I could have done with my normal knee,” he said.

A recent study shows that he’s not alone, claiming that patients receiving this knee system had a 97 percent satisfaction rate at one year and 98 percent at two years.

Nor is this Fuller’s first rodeo. He had his right knee replaced in a more traditional procedure about five years ago. When comparing the results, he describes the feel of the right knee as “sloppy.”

“With the first knee, after a two-and-a-half hour surgery, I was black and blue from my butt to my heel on the back side of my leg,” Fuller said. “With Dr. Blackwood, the surgery was about 35 minutes, and I didn’t have a bruise except right at the incision.”

The procedure was developed on the West Coast about four years ago, and BCH is currently the only health facility in Colorado where it is available. Blackwood said that despite a price of several hundred dollars for the orthosensor implants, there is no extra charge for patients. The hospital is absorbing the additional cost, with an eye toward long-term benefits.

“One of the early causes of failure for knee replacements is instability, a function of a poorly balanced knee or poor tracking, and so if we can do a better surgery the first time it reduces a lot of costs down the road.”

“Knee replacements are sort of where art and medicine combine,” Blackwood said, “and if we can add more science to that art, give people more information, I think that will give patients much better outcomes, better-performing knees.”

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