New Discoveries

How Computer Models Can Advance Pressure Ulcer Research: Part 2

In part 1 of this series (MM June 2014), Amit Gefen, Ph.D., a professor of biomedical engineering at Tel Aviv University, discussed a new means of studying the critical issue of pressure ulcers. This news comes as the complex rehab technology industry is under increasing pressure to provide outcome measures — i.e., proof that its technology works. In part 2, Gefen — who has degrees in mechanical and biomedical engineering — explains how computer technology and lab-engineered tissues can help researchers to better anticipate skin breakdown…and the potential impact of that tool.

How Computers Can Contribute

One of the huge benefits to using computers in pressure ulcer research is the ability to mimic the various medical conditions that seating clinicians see when working with wheelchair-using clients.

“You can simulate transient events, like spasms,” Gefen says. “You can simulate long-term changes, like bone structure changes, muscle atrophy, invasion of fat plaque tissue into muscle, asymmetries.”

For instance, a computer could be used to show the effect of a lower-extremity amputation: how asymmetrical weight distribution during sitting could result.

Gefen points out, “Another thing is osteotomies” — the surgical cutting or removal of bone. “In someone who has a grade 4 pressure ulcer and it complicates into osteomyelitis [bone infection], what they do almost always is cut bone. So basically, one ischial tuberosity is intact, and the other is gone. You can simulate that with computer tests to see what it will do in seating, not in terms of what you see from the outside, but what happens internally, which is probably where the injury starts.”

So let’s say you have a client with a lower-extremity amputation whose body weight is distributed asymmetrically when he sits in his wheelchair. Could computer simulations predict whether or not he would experience skin breakdown — and if so, when?

“I want to be careful here,” Gefen says. “We can’t really predict that far in the future. We can predict trends, like patient populations.”

The reason: Gefen says factors that vary from client to client have a huge impact on eventual outcomes.

“Think about transient events in the life of a patient,” he says. “If that patient suddenly gets pneumonia, that will affect his level of tissue oxygenation. That’s a transient event that adds on top of all the factors you have. It’s really complex.”

Predicting Trends in Patient Populations

So a computer can’t presently forecast the outcome for a particular patient because each patient has so many unique variables that could affect the end result.

“But at least you can get some understanding of the trends of events,” Gefen notes. “Much like in cancer. When you see a tumor of a certain size, based on knowledge you can evaluate how it’s going to evolve. But that doesn’t mean you will be able to predict whether that patient will live or die, or how much time that will take.”

Due to the large numbers of people who have had cancer and the volumes of research done on the disease in the past, today’s physicians can tell their patients what to expect or what might happen next. Those sorts of studies aren’t possible in the much smaller realm of wheelchair users.

“The computer simulations basically substitute for other people’s experiences because other people’s experiences will take huge clinical trials, which you cannot really do in this field,” Gefen explains. “If you look at hypertension or high cholesterol or common conditions, then you can do studies with thousands of patients. If you want to study a thousand pressure ulcers, do you know how many patients you will need? If you follow a spinal cord injury patient, you have, say, a 20-percent likelihood that he will develop a pressure ulcer over 10 years. So who’s going to do that?”

The flip side, Gefen points out, is that if that patient does develop a pressure ulcer, it could be deadly.

“I was one of the first to provide the evidence that deep-tissue injuries exist, and then to provide the etiology of how they develop,” he says. “And this is really my focus because deep-tissue injuries, as opposed to all these skin lesions, you don’t see them. They’re very tricky, and when you see them, it’s too late.”

What was needed was a way to detect injuries as early as possible.

“You have to develop some kind of way to screen and to assess risk and eventually to also earlier identify the actual injury, when it starts, for example at the bone/muscle interface,” Gefen says. “But these patients are at home, or even if they’re in a hospital, [clinicians] won’t scan them with ultrasound, not to mention an MRI, every two hours. So this is not the way.”

What did work: Using an open type of MRI machine rather than the conventional enclosed MRI device. While the open MRI lacks the sort of extreme definition and clarity of detail that a traditional MRI exam offers, Gefen points out, “In an open MRI, you can do sitting studies.”

What Gefen wanted to study: “The very basic thing we wanted to know is what is the level of loading internally? Not to guess it, not to estimate it — to measure it.”

Coming up in Part 3: How MRI results, combined with computer models and lab-generated tissues, gave researchers the ability to create formerly impossible pressure and weight distribution scenarios…and what this all means to the wheelchair seat cushion industry.

This article originally appeared in the August 2014 issue of Mobility Management.

About the Author

Laurie Watanabe is the editor of Mobility Management. She can be reached at

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