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Williams' Research to Aid Surgeons During Replacement Surgery

By: Sara Hoover

Dr. John L. Williams
Dr. John L. Williams

Dr. John L. Williams does not work on cars and is not up to his elbows in grease.

The professor of biomedical engineering in the Herff College of Engineering does work with Adams/View, the most widely used software in the auto industry.The interactive motion simulation software allows engineers to create models of mechanical systems and run simulations. The results are viewable as graph, data plots, reports and colorful animation that can be shared with others. The software is also used in aerospace, but Williams is not using it in either of those industries. 

With a $400,000 soft-ware grant from the California-based company, LifeModeler Inc., Williams is developing KneeSIM that will improve the orthopedic surgery of knee replacements. Splitting his time at the U of M and at the InMotion Musculoskeletal Institute as its director of biomechanics, Williams is helping to perfect KneeSIM, built from Adams/View. KneeSIM uses virtual knees to understand how joint replacements behave and get an estimate of what the muscle forces and joint forces will be before a single incision on a patient is made.
"When I picked it up, KneeSIM did not allow us to answer clinical questions surgeons were asking. It only had basic functionality," Williams said. 

Using the groundwork already laid by Adams/View, Williams is fine-tuning KneeSIM to vary tissue fidelity, the anatomy, different size bones and, most importantly, the positioning of the implant within the software. 

"When I started working with this, it was relatively crude," he said. "Some of the big things we added: muscles, soft tissue around the capsule and point-to-point ligaments. I have the ability to put in lots of them and different values."

Knee replacement procedures have been done for the past 30 years and their success has been measured by if a patient can walk, bend their leg and if they feel pain. Atypical knee replacement usually lasts for 20 years. Joint replacements are expected to do more and last longer now that they are being put in younger patients.

"Younger patients want to be able to do things -jogging, bicycling. With knee replacement, you can't do high impact physical activity. People expect to be able to do more. Now, it's more important to come up with physical implants that allow you to do these things. One of the problems has been (patients) can't bend their knees as much as they'd like. The challenge now is how to come up with an implant that allows people to flex their knee more."

That's where Williams' work comes in. With KneeSIM, he can do the theoretical lab work before it ever gets into the hands of the surgeons in a much shorter time period. Two people took a week to work out these calculations with pencil and paper.What was a very slow process that took four hours a day is now down to a couple of minutes. This time saver can then be used in the operating room, where surgeons can easily try different positions of the virtual implant and see immediately how it would change the outcome.

"You don't want to have a new design and put it in a patient and find out how it works that way.You want to be able to (know) before you get to that," Williams said.

Dr. John L. Williams
Dr. John Williams work will aid surgeons who are performing knee-replacement surgeries. (Lindsey Lissau photo)

With this much faster tool for communicating with surgeons, Williams can try different solutions and test them in the virtual world rather than with an actualmetal-on-polyethylene knee prosthesis in a cadaver leg - a current form of testing. Surgeons perform the joint replacement on cadaver legs, which are then put in a machine that bends the leg and puts force on it, but there are limitations to that process as well.

"Turns out you can't apply the full force to the leg because if you can't pull it back up again, you'll just tear all the tendons out," Williams said. "There are limitations in what we can do. Every surgeon that puts one of these in is going to put it in slightly differently. Every knee is going to be different. You get this whole range of different outcomes and you don't know why."

With KneeSIM, he doesn't have the same restrictions. 

"There's a lot of limitations in this (cadaver) experiment we can get around. What we have is a virtual model. It's taking the implant, putting it in the virtual knee and putting it in a virtual machine," Williams said.

The software is a significant tool for orthopedic surgeons because it shows what happens when the replacement is at different angles and how that can change a patient's walk and angle to other bones.

"Whether (surgeons) place it at the angle they think they're placing it at, even if they use computer-assisted surgery, one of the questions is: Is the slope in the wrong direction? Because you're going to get variations with the cutting tools, and see what's the effect if you do that. It doesn't take very long; you can investigate. The other thing we now know is the angle between the quad and this little tendon that goes through the patella --referred to as the Q angle -- we know that it is different in men and women. If a person's Q angle is changed, that really changes how they walk."

For testing purposes, changing someone's Q angle is very difficult. In the software, it can be changed. Some implants rotate the opposite direction than a normal knee would, in a direction the patient doesn't want to go in. Problems like this that would be complicated to try in reality can be tested in the software.

This is the first time anyone's been able to use these simulation tools in this manner.

The software is patented by Lifemodeler, which also has whole body software called BodySIM that is used by NASAas part of their spacesuit design and also for projects by the army.

As far as orthopedic surgeons using the KneeSIM software, Williams says that won't happen until "the market starts to be driven toward higher function, functional outcome and tissue procedures.

"The only thing that will change it is when one of the companies creates a better product and others start worrying, 'How can we do this?' and the demand for better function, which you just can't achieve with traditional surgery," Williams said.


(To watch a video of Williams' research click here)

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