A Model Foot

Diabetes patients often suffer from problems in their feet, including sores and loss of feeling. East Carolina University researchers are using sonograms to see the foot in a new light in an attempt to help.

GREENVILLE — The image on the screen in the Biomechanics Laboratory at East Carolina University looks a lot like the ultrasound image expectant parents proudly show off to family and friends—except this isn’t the maternity ward of a hospital.

“She’s looking for the muscles and tendons in the foot, and as she goes through she is also looking at the stiffness of the tissues,” says Dr. Zachary Domire, an associate professor in the Department of Kinesiology at East Carolina University.

The imaging is part of a research project at East Carolina University that is hoping to find the cause, cure and a way to prevent diabetic foot ulcers. It’s one of the most challenging medical issues facing diabetes patients.

“Individuals with diabetes have a high risk of ulcers on their feet,” explains Dr. Domire. “Diabetic foot ulcers are a terrible problem for people who get them. Plus the problem can recur frequently, and in many cases may lead to the amputation of a limb.”

The East Carolina researchers believe the underlying cause of those ulcers is the stiffness of the feet since foot stiffness is a problem for diabetes patients. The hypothesis for the project is that as the foot becomes stiffer it is less able to deform and spread out the pressure forces on the foot. That results in higher pressure in areas where there is impact on the foot.

You may not think about it, but there are multiple forces acting on your feet while you are walking. Forces impact the heel as it strikes the ground, those forces travel the length of the foot and then pressure is applied to the ball and toes as the foot pushes off the ground.

Researchers study those forces using multiple cameras to create 3D computer images. Those images are then used to calculate the amount of force being applied to the joints and muscles in the body.

“So as Sidney walks forward you can see the force vector gets large initially, it reduces a bit, and then gets larger again as she pushes off,” explains Dr. Paul DeVita, Director of the Biomechanics Lab in the Department of Kinesiology at East Carolina University. He points to a computer monitor showing a person outlined in a series of dots. There are arrows shooting up from the ground into the body.

“So this is the exact pattern of force Sidney applies to the ground to do her walking movement,” adds Dr. DeVita. “But an older adult, or an adult with osteoarthritis or various types of leg injuries would apply a slightly different pattern because we all move a little different by using muscles a little differently and applying slightly different forces.”

The issue is easier to see when you are walking barefoot on a beach. Have you ever noticed how your foot seems to expand a bit when you step? That expansion spreads out the forces that are impacting the bottom of your foot.

Shoes limit that expansion somewhat. That’s why tight shoes are uncomfortable. That’s also why many people try softening the impact of walking by inserting pads in their shoes. 

But diabetes patients often lose feeling in their extremities, especially their feet and may not feel a wound developing. And because diabetes patients also suffer from poor circulation in their extremities, healing a wound is difficult.

The researchers at East Carolina believe that the combination of pressures on specific areas of the foot caused by the stiffness of the foot combined with a lack of feeling in the limb and poor circulation all contribute to the serious problem of foot ulcers in diabetes patients.

“While the other things are needed to develop an ulcer, the ulcer is really coming from the high pressures,” adds Dr. Domire. “The high pressures are what is damaging the tissue.”

Researchers are studying muscle, tendons and skeletal structures as well the mechanics of the foot trying to find multiple ways to alter the stiffness of the foot. The best way to do that is with an ultrasound. The project has imaged and studied hundreds of pairs of feet.

“First and foremost you have to have a very steady hand because with the kind of measurements we need for cross sectional and thickness values of tendons and tissues, you need really clear images,” says graduate student Erica Bell, as she moves the sensor over the bottom of a patient’s foot. The gel needs to be continuously smoothed out to the required thickness so the sound waves will be transmitted from the sensor into the foot. For Bell, the research is personal.

“My mother has type 2 diabetes, and she has a lot of issues with her feet,” adds Bell, watching the ultrasound images on the screen move from yellow to red as the stiffness of the tendon increases. “I always need to go home and rub her feet because they are stiff and hurt so much.”

Researchers want to see if the stiffness of the foot can be altered mechanically, perhaps by using new physical therapy techniques that stretch the muscles and tendons. The project is also opening up the potential for new medicines.

“We’re looking at all types of options because when I look at the human body I’m amazed we can do what we do, especially when you look at the muscles,” says Matthew Salzano, a graduate student in Biomechanics who is also working on the foot ulcer project. “When you look at the forces they can produce, we don’t use the full potential.”

The U.S. Centers for Disease Control reports 29 million Americans are diagnosed with diabetes. It’s estimated that roughly the same number of people have the disease but have not been diagnosed. There are plenty of people who could be helped by what East Carolina researchers discover.

Related Resources: