By: Sara Hoover

Dr. John L. Williams

“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 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, visit http://memphis.edu/videos/)

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