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Analysis of Foot and Ankle Deformity Using the Milwaukee Foot Model and Biplane Fluoroscopy - Research and Translation to Clinical Care
Dr. Karen Kruger discusses the development of the Milwaukee Foot Model and how it helps analyze foot and ankle deformities.
Featuring:
Karen Kruger, PhD
Learn more about Karen Kruger, PhD Transcription:
Melanie Cole, MS (Host): Welcome. Today we’re talking about the exciting Milwaukee foot model and biplane fluoroscopy. If that sounds confusing and technical to you, it’s really not. We’re gonna learn about this exciting technology from Dr. Karen Kruger. She’s the motion analysis center and engineer at Shriners Hospitals for Children in Chicago. Dr. Kruger, as I said in the intro, for some listeners this might sound pretty technical and a little bit confusing. Tell us about the development for the Milwaukee foot model. What is it and how did it start?
Karen Kruger PhD (Guest): So the Milwaukee foot model is a segmental foot and ankle model that we use to evaluate gait in the motion analysis center. So typically when a kid with a movement disorder is being considered for orthopedic surgery or another intervention, they come into the gait lab and we can calculate all of their joint angles and muscle forces. However, the model we use to evaluate walking that’s pretty standard models the foot as just a single rigid segment. If you’ve ever tried to study foot motion, you learn pretty quickly that the foot’s extremely complex with so many bones and tendons and muscles moving around. So if we have any sort of foot pathology we’re interested in analyzing, the single segment representation wasn’t really telling us enough information.
So that kind of clinical need drove the development of the Milwaukee foot model, which started out as a PhD project in bioengineering up at Marquette University. So it went thorough a pretty extensive validation process including being validated for use in pediatric cases. So after that whole process took place, we were able to start using it in research and now clinically in applications like characterizing specific foot conditions, identifying differences between typical and atypical motions, tracking progression of deformity, and then evaluating post-surgical outcomes. So the model went from being a PhD dissertation project to being in regular use in our motion analysis centers where our therapists can use it on any kid that they think it would be beneficial for with things like Plano valgus, equinovarus, club foot, or tarsal coalition.
Host: That’s so cool how that really works, and you really explained very well how something goes from research applications to use in the clinic. That’s such great information for listeners. So tell us a little bit about how it works for some of these conditions you mentioned. Club foot. Tell us, how is this working? As they model is being used clinically, what improvements would you make to it?
Dr. Kruger: So right now it models several segments. We look at the tibia, the hindfoot motion, forefoot motion, and the hallux motion. If you have a foot deformity like Plano valgus or equinovarus, they're characterized as the same foot deformity, but they might have different involvement. Like sometimes the deformity is characterized mainly in the hindfoot and sometimes it’s more focused on the forefoot. So if the surgeons are trying to decide which surgery is most appropriate, they can use those results to show where are we seeing deviations from normal motions and maybe we can target the surgical procedure to that specific area.
So right now it’s limited in that we can calculate kinematics, which are the angles between the joints, but we can't get the kinetics or the forces and moments that all of the joints are getting or the muscle lengths. So we’re working to improve on those technical areas. One of the exciting things we’ve been working on is a software called OpenSim which actually lets us calculate how muscle links are changing while a person’s walking. So a lot of the surgical procedures that the surgeons are looking at doing are lengthening or shortening a muscle to help the foot function better. However, the software right now is similar to the lower extremity model in that it models the foot in a rigid segment. So we’re working to get those specific Milwaukee foot model criteria into the model so that we can give the surgeons better data for their preoperative planning.
Host: That’s so important. As you say, the foot is such a complicated joint collection of bones. It’s really complicated. What you're doing there is amazing and so technical. So now tell us, and for the listeners explain what is biplane fluoroscopy? What are some of the benefits? What is biplane being used for? What is fluoroscopy?
Dr. Kruger: So fluoroscopy is x-ray. So what the biplane fluoroscopy system can do is actually get us an x-ray video of someone’s foot walking over ground. One reason this is really important, a lot of the foot patients we see have deformities specifically focused at the hindfoot. So there’s three bones that we’re looking at. The tibias, talus, and calcaneus. In the gait lab we rely on placing markers at different anatomic landmarks, but the talus—that bone in the middle—doesn’t have anywhere we can access to place markers. So the only way we can really see how those joints are moving is under this biplane fluoroscopy. So that lets us see what those joints look like while a subject is walking.
The other big improvement is with gait analysis. We typically either do it barefoot or in shoes if the subject has trouble walking or AFOs. When we’re evaluating them in shoes or AFOs, we’re assuming the foot is doing what the shoe is doing, but we’ve never really been able to see if that’s right. So this fluoroscopy will let us actually see inside of the shoe so you can see what the bones and the foot’s doing inside of the shoe, which we’ve never been able to do with our standard motion analysis technology.
Host: How cool is that? So why is this important for parents to know? The fact that it’s being used now in clinics, how can it help advance the technology that are making better outcomes for patients, Dr. Kruger?
Dr. Kruger: So I think it’s important that they know that we’re using the most advanced segmental foot modeling and biplane fluoroscopy of any pediatric hospital in the country. I think the benefit of being involved with biomedical engineering at Marquette University has really been able to keep our motion analysis center on the forefront of all of these new technological advances. The other big benefit of our motion analysis center is we have regular case reviews with the orthopedic surgeons, therapists, and engineers. So our engineers are constantly hearing what the surgeons need and how we can better help them.
Host: Absolutely fascinating. Thank you so much Dr. Kruger for coming on today and explaining this to us. It’s so interesting. Thank you again for joining us. That wraps up another episode of Pediatric Specialty Care Spotlight with Shriners Hospital for Children Chicago. You can head on over to our website at shrinerschicago.org for more information on this topic. Until next time, I'm Melanie Cole.
Melanie Cole, MS (Host): Welcome. Today we’re talking about the exciting Milwaukee foot model and biplane fluoroscopy. If that sounds confusing and technical to you, it’s really not. We’re gonna learn about this exciting technology from Dr. Karen Kruger. She’s the motion analysis center and engineer at Shriners Hospitals for Children in Chicago. Dr. Kruger, as I said in the intro, for some listeners this might sound pretty technical and a little bit confusing. Tell us about the development for the Milwaukee foot model. What is it and how did it start?
Karen Kruger PhD (Guest): So the Milwaukee foot model is a segmental foot and ankle model that we use to evaluate gait in the motion analysis center. So typically when a kid with a movement disorder is being considered for orthopedic surgery or another intervention, they come into the gait lab and we can calculate all of their joint angles and muscle forces. However, the model we use to evaluate walking that’s pretty standard models the foot as just a single rigid segment. If you’ve ever tried to study foot motion, you learn pretty quickly that the foot’s extremely complex with so many bones and tendons and muscles moving around. So if we have any sort of foot pathology we’re interested in analyzing, the single segment representation wasn’t really telling us enough information.
So that kind of clinical need drove the development of the Milwaukee foot model, which started out as a PhD project in bioengineering up at Marquette University. So it went thorough a pretty extensive validation process including being validated for use in pediatric cases. So after that whole process took place, we were able to start using it in research and now clinically in applications like characterizing specific foot conditions, identifying differences between typical and atypical motions, tracking progression of deformity, and then evaluating post-surgical outcomes. So the model went from being a PhD dissertation project to being in regular use in our motion analysis centers where our therapists can use it on any kid that they think it would be beneficial for with things like Plano valgus, equinovarus, club foot, or tarsal coalition.
Host: That’s so cool how that really works, and you really explained very well how something goes from research applications to use in the clinic. That’s such great information for listeners. So tell us a little bit about how it works for some of these conditions you mentioned. Club foot. Tell us, how is this working? As they model is being used clinically, what improvements would you make to it?
Dr. Kruger: So right now it models several segments. We look at the tibia, the hindfoot motion, forefoot motion, and the hallux motion. If you have a foot deformity like Plano valgus or equinovarus, they're characterized as the same foot deformity, but they might have different involvement. Like sometimes the deformity is characterized mainly in the hindfoot and sometimes it’s more focused on the forefoot. So if the surgeons are trying to decide which surgery is most appropriate, they can use those results to show where are we seeing deviations from normal motions and maybe we can target the surgical procedure to that specific area.
So right now it’s limited in that we can calculate kinematics, which are the angles between the joints, but we can't get the kinetics or the forces and moments that all of the joints are getting or the muscle lengths. So we’re working to improve on those technical areas. One of the exciting things we’ve been working on is a software called OpenSim which actually lets us calculate how muscle links are changing while a person’s walking. So a lot of the surgical procedures that the surgeons are looking at doing are lengthening or shortening a muscle to help the foot function better. However, the software right now is similar to the lower extremity model in that it models the foot in a rigid segment. So we’re working to get those specific Milwaukee foot model criteria into the model so that we can give the surgeons better data for their preoperative planning.
Host: That’s so important. As you say, the foot is such a complicated joint collection of bones. It’s really complicated. What you're doing there is amazing and so technical. So now tell us, and for the listeners explain what is biplane fluoroscopy? What are some of the benefits? What is biplane being used for? What is fluoroscopy?
Dr. Kruger: So fluoroscopy is x-ray. So what the biplane fluoroscopy system can do is actually get us an x-ray video of someone’s foot walking over ground. One reason this is really important, a lot of the foot patients we see have deformities specifically focused at the hindfoot. So there’s three bones that we’re looking at. The tibias, talus, and calcaneus. In the gait lab we rely on placing markers at different anatomic landmarks, but the talus—that bone in the middle—doesn’t have anywhere we can access to place markers. So the only way we can really see how those joints are moving is under this biplane fluoroscopy. So that lets us see what those joints look like while a subject is walking.
The other big improvement is with gait analysis. We typically either do it barefoot or in shoes if the subject has trouble walking or AFOs. When we’re evaluating them in shoes or AFOs, we’re assuming the foot is doing what the shoe is doing, but we’ve never really been able to see if that’s right. So this fluoroscopy will let us actually see inside of the shoe so you can see what the bones and the foot’s doing inside of the shoe, which we’ve never been able to do with our standard motion analysis technology.
Host: How cool is that? So why is this important for parents to know? The fact that it’s being used now in clinics, how can it help advance the technology that are making better outcomes for patients, Dr. Kruger?
Dr. Kruger: So I think it’s important that they know that we’re using the most advanced segmental foot modeling and biplane fluoroscopy of any pediatric hospital in the country. I think the benefit of being involved with biomedical engineering at Marquette University has really been able to keep our motion analysis center on the forefront of all of these new technological advances. The other big benefit of our motion analysis center is we have regular case reviews with the orthopedic surgeons, therapists, and engineers. So our engineers are constantly hearing what the surgeons need and how we can better help them.
Host: Absolutely fascinating. Thank you so much Dr. Kruger for coming on today and explaining this to us. It’s so interesting. Thank you again for joining us. That wraps up another episode of Pediatric Specialty Care Spotlight with Shriners Hospital for Children Chicago. You can head on over to our website at shrinerschicago.org for more information on this topic. Until next time, I'm Melanie Cole.