MOUNT VERNON — Jack Gribble’s knee problems started in 1978 following a motorcycle crash.

“I ended up with one leg shorter than the other,” Gribble said. “Through the years, it caused additional wear and tear on that knee.”

Nearly four decades later, Gribble underwent robotic-assisted surgery at Skagit Northwest Orthopedics in Mount Vernon. The robot — the first one used in the state — helped Dr. Daniel Hanesworth perform the partial knee replacement surgery with greater planning and precision.

“It does so much,” Hanesworth said while standing in the operating room in light blue scrubs. “It lets us make a more naturally performing knee.”

The center purchased the robotic assistant, called the NAVIO system, for $500,000 and put it into use in April. The center has performed about 35 partial knee replacement surgeries with the tool.

The robotic assistant consists of four main parts: a camera, a computer, a handheld stylus-like probe that draws a picture of the knee, and a handheld robotic cutting tool.

Holding the stylus tool and a model knee joint, Hanesworth explained the planning process.

After cutting open the tissue over the knee, the surgeon “paints” the exposed knee with the stylus, creating a 3-D model of the knee that is displayed on the computer.

The computer automatically designates the portion of the knee — highlighted in purple on the computer screen — that will be cut out and replaced with an artificial implant. Hanesworth can then makes adjustments on the 3-D model.

“We manipulate it around to get the exact balance and motion we want,” he said.

During surgery, Hanesworth holds the robotic cutting tool as it automatically cuts the bone. The camera can sense where the tool is positioned and only cuts the designated portion of the knee.

All Hanesworth has to do is hold the tool in the proper place — if his hand drifts off course, the tool stops cutting.

“It’s amazing just how precise it is,” he said.

Using the robotic assistant, Hanesworth and other surgeons at the center have had to make certain adjustments.

Instead of looking at the patient’s knee, Hanesworth said he now mostly stares at the computer screen to make sure the cutting tool is positioned over the purple areas designated for cutting.

“This is where I wish I was more of a (video) gamer when I grew up,” he said. “Probably my son would be OK at it ... It’s actually much easier to look at the screen to make sure you are getting all the spots. The color of the cuts goes from purple to green to white. Once it’s white, that means you have taken off all the bone.”

After all the cutting, the surgeon adds the replacement implant.

The surgery lasts about an hour, with all the planning done right before the operation, Hanesworth said. The bonus for patients is they can skip a CT scan, which is used for planning traditional knee replacements.

Hanesworth said this kind of robotic assistant for partial knee replacement is the first of its kind in the state. There are other kinds of robotic assistants, but none like the NAVIO.

“There are some more traditional-looking robots that are more like arms that the surgeon controls,” he said. “This is very compact compared to other systems.”

His system is only capable of performing partial knee replacements. He said that will likely change as the company that makes the robotic assistant works to gain approval for full knee replacement.

Gribble said he felt an immediate change a couple hours after his May 10 surgery.

“I was up on my feet and I realized that I had been living with that pain and discomfort for so long,” he said. “As soon as I got up I could tell there was absolutely no pain in the joint itself.”

What astonished him the most is he was able to complete a cross-fit workout three weeks later: 300 squats, 200 pushups, 100 pullups and a 1-mile run.

“I was able to do that workout May 31,” he said. “It was amazing.”

— Reporter Aaron Weinberg: 360-416-2145,,

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