Can Smart Orthotics Have An Impact In Preventing Ulceration?
Furthermore, Dr. Erdemir notes that dynamic stability during walking without adequate shear forces may be an issue. He suggests that computational modeling studies are likely to be helpful to identify potential orthotic designs.
Although insoles that target pressure work in a straightforward way, Dr. Davis says in the case of shear, it may be the relationships between neighboring regions that are important. As he explains, if an insole is designed to reduce skin shear in region A, then increased shear is likely in region B. Depending on the direction of shear, Dr. Davis notes this could either result in skin “bunching” and/or skin “stretching” in other regions. If one designs an insole to reduce friction over the entire plantar surface, he says slippage will occur within the shoe and the patient may experience skin damage on the dorsal surface of the toes.
Dr. Yavuz notes a significant dilemma. While it may be possible to reduce shear forces under the foot with an orthotic design, he says this would come at the expense of increasing the repetition count of mechanical factors. He notes that shear forces, particularly propulsive shear forces, are associated with speed and step length during normal gait. If there is a constant cadence, Dr. Yavuz says the higher the propulsive shear forces under the foot, the longer steps the patient takes and the faster the patient walks. Therefore, if patients wear orthotics that reduce shear forces under the foot, Dr. Yavuz says they will need to take a greater number of steps to traverse a certain distance.
Dr. Yavuz cites Brand’s research that the repetition count of mechanical forces is as important as their magnitudes in tissue breakdown.9 As he explains, if a patient takes more steps every day to go to work when wearing such orthotics, his or her foot may still ulcerate even if the shear forces under the foot are lower.
However, Dr. Yavuz cautions against drawing sharp conclusions in this matter without knowing at what force (magnitude x repetition) combinations the skin will break down. It is crucial to obtain such data, at least from animal or cadaver models, so one can design diabetic orthotics optimally, according to Dr. Yavuz.
What is your opinion on the availability of “smart” orthotics and footwear?
Dr. Yavuz notes he and other researchers are working on such smart orthotics, which will record variables like pressure, shear, temperature, humidity and number of repetitions within the shoe, and alert patients when they reach thresholds for those variables. He says Michael Mueller, PhD, PT, was working on a funded research project regarding the development of such a device. Although
Dr. Yavuz does not know the end result of this particular project, he feels the mission is not too far away from being accomplished.
Dr. Erdemir notes researchers must overcome two hurdles to make smart orthotics. The first is acquiring the technology to measure the aforementioned variables. While daily logging of plantar pressures is not necessarily an issue, Drs. Erdemir and Davis say in-shoe measurement of shear, temperature and humidity will likely require considerable engineering research in the near future.
“The inside of a person’s shoe is a harsh environment and getting electronic circuitry to withstand the daily demands imposed by human locomotion is a very challenging problem,” notes Dr. Davis.
Dr. Yavuz feels it is relatively easier to measure pressure, temperature, humidity and activity in shoe conditions. He feels the challenge is in quantifying shear forces under the foot. Dr. Yavuz is currently collaborating with a
medical device design company to achieve this goal of measuring plantar shear force distribution in shod. However, Drs. Yavuz and Erdemir concur that risk thresholds for these parameters remain elusive.
“Do we really know what magnitudes and numbers of repetition of pressure, shear, temperature and humidity put someone at risk?” questions Dr. Erdemir. “We are in need of significant amount of biomechanical and clinical studies to establish this information.”
Dr. Davis is skeptical about the potential cost of smart orthoses.