GPS Improves Knee Replacement Surgery

With its lengthy and painful recovery period, knee replacement surgery is always a last resort. But with the number of American seniors on the rise, the procedure is being performed more often than ever. More than 700,000 knee replacements were performed in the U.S. last year.

One major drawback is that the surgery occasionally needs to be redone, or "revised," because, even for experienced surgeons, deciding where to place a prosthetic knee is not an exact science. That is, until now.

Dr. Jaime Hernandez of the Southern California Orthopedic Institute in Los Angeles is one of just a few surgeons in the country using sophisticated computers to implant artificial knees with precision. The OrthoSensor Verasense technology and Stryker computer navigation system use GPS, infrared cameras, and a pressure sensor to help Hernandez place the prosthetic knee.

The same technology that helps motorists find their way out of traffic jam helps Hernandez align the knee for optimal comfort and function. The result is a shorter recuperation time and greatly reduced risk of having to repeat the procedure.

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Procedure Puts Cop Back on the Beat

Sandra Liddy is an officer with the Los Angeles Police Department. Hernandez used the new technology to replace both of her knees, one last November and the other in March.

She had injured herself on the job during a training exercise designed to prepare cops in the event of a New Year’s Eve riot. Although the trainer warned the officers “Don’t be pushing and running,” that’s exactly what happened, Liddy told Healthline.

“You know cops, we’re human,” she said. “Sure enough, we were running and pushing. I got pushed and went down.”

Liddy’s jeans tore and her knees sustained severe abrasions. She has gravel inside of her legs to this day. “They couldn’t get it all out,” she said.

She suffered in pain for six years. Multiple traditional surgeries, including arthroscopic surgery, offered little relief. She had lost her menisci (a cushion between bones in the knees) and was coping with the agony of bone-on-bone pain when she walked.

Liddy tried shots of Synvisc, a knee lubricant designed to ease bone-on-bone pain, but the relief “barely lasted a month,” she said. Finally, a well-known Los Angeles orthopedist told her there was nothing more he could do, and sent her to Hernandez.

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From Gut Feeling to Exact Science

What’s so special about the technology Hernandez uses, and the high-tech operating room where he performs surgery?

Infrared cameras are used to map the patient’s anatomy and calculate alignment of the leg, from the hip to the knee to the ankle. “Most people who have a worn out knee may be bull-legged, knock-kneed, or hyperextended,” he said. “The computer measures the deformity to allow for a correct and straight leg.”

“An analogy is that if you don’t align tires, they wear out sooner." — Dr. Jaime Hernandez

In traditional knee replacement surgery, a plastic spacer is used inside the knee while the surgeon tests range of motion. This is done to determine the best placement for the prosthetic. The surgeon essentially relies on how the leg “feels” during the test.

“It’s more about eyeballing and feeling it,” Hernandez said of the traditional method. “It sounds surprising to hear, but that’s how it’s done.”

Instead, Hernandez uses an intelligent spacer. This spacer is embedded with censors that measure load and tension in real-time during range of motion tests. The idea is to help Hernandez determine the correct size of the knee prosthetic. “You don’t want it to loose or too tight,” he said. “Nobody wants a stiff or sloppy knee.”

While Hernandez tests range of motion, the data is displayed on a monitor, giving the surgeon quantifiable data about the load the prosthetic will be required to handle. Hernandez says that his method allows the prosthetic to wear more evenly. “An analogy is that if you don’t align tires, they wear out sooner,” he said. 

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Costly Equipment Improves Safety

Hernandez said knee replacement surgery using his high-tech method doesn’t cost any more than the traditional surgery. The equipment itself, however, is expensive. Not many hospitals are willing to pay half a million dollars for each computer, he said, especially when the technique is less than 15 years old.

The OrthoSensor website has a doctor locator for patients trying to find surgeons near them who perform knee replacements with this new equipment.

Hernandez believes the equipment is worth the price, especially since it results in less blood loss during surgery because the procedure is less invasive. He said that this procedure also cuts down on the release of emboli, small pieces of fat that can be released during surgery and lead to a stroke.

Liddy said it was important for her to have a quick recovery time and not to be reliant on painkillers for very long. “I don’t want to be that type of person, an L.A. city employee on drugs.”

“I’m very active,” Liddy added. “I’m an ants-in-the-pants type of girl as a cop.”

Hernandez said he has lots of patients who are police officers and firefighters. He enjoys seeing his patients get back to business shortly after surgery.

“It’s not going to be the perfect knee of a 17-year-old, but they should be able to do anything they need to do but be an Olympic gymnast,” Hernandez said. “I have one guy who sends me pictures of him crossing finishing lines, even though I tell them they’re not supposed to run marathons.”

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