Pressure ulcers are insidious, but traditional wisdom has said they could be prevented by diligently performing skin checks. At-risk populations and their families/caregivers have been advised to look for the changes in skin temperature, color and texture that can signal skin breakdown. Ischemia, the lack of adequate blood supply to skin under unrelieved pressure, was thought to typically be the cause of pressure ulcers, also known as pressure sores or bedsores.

But new research has pulled back the curtain on pressure ulcers to reveal additional causes and results that are much more difficult to detect. Deep tissue injuries (DTI) happen internally, and therefore don’t necessarily cause the reddened or warmer skin that has been a trademark of a developing pressure ulcer. With this evolution in understanding comes a critical question: What will clinicians, ATPs, seating manufacturers and other stakeholders do with this newly discovered information?

Deep Tissue Injury Formation

Recent and ongoing research by Amit Gefen, Ph.D., professor of biomedical engineering at Tel Aviv University, and Kara Kopplin, BSc, the Senior Director of Efficacy & Research for ROHO Inc., has focused on pressure-related deep tissue injuries (see Mobility Management, September 2015).

A mechanical engineer by training, Gefen approaches the problem of pressure ulcers via a different route than that commonly taken by seating professionals. When you talk with him, as Mobility Management did over breakfast for a second consecutive year at the 2015 International Seating Symposium in Nashville, Tenn., the conversation is full of mentions of forces and loads and structures.

“We know that exposures to tissue deformation are putting the tissue at risk, and since we know that the more serious pressure ulcers are deep tissue injuries that start from the inside, we know where to look,” he says. “The highest tissue loads are at the bone/soft tissue interface.”

Taking the ischial tuberosity (IT) as an example, Gefen mentions what has long been understood in the seating realm: When the IT presses down on the tissue and skin beneath it for unrelieved periods of time, damage can occur.

“It’s the sharpness of the bone which is deforming the tissues,” Gefen says of the rather pointed IT depressing the soft tissue of the buttock. During the discussion, with one hand he held a knife vertically as a visual aid and lightly pressed its point against the palm of his other hand. “It’s like taking this knife here and if I do this, I’ll be able to cut through. And the reason for that is the sharp tip of the knife is focusing all the force I’m delivering with my hand in one very small area.” In the case of the IT, he says, “You have the sharp tip of the bone which is compressing against a very small area of soft tissue, and that’s where you have these great forces.”

Kopplin says the traditional concern of a lack of bloodflow resulting in what’s been called “skin breakdown” is only part of the real issue — which has just recently begun to be understood. “Last year and two years ago, it was still all this talk about ischemia,” she says. “They were barking up the wrong tree. [DTI] is what is more critical.”

Gefen agrees: “Once you understand deformation, and you connect that with the clinical manifestation of DTIs, then you really understand what’s going on here.”

Applying New Knowledge

Having come to this new understanding of deep tissue injuries through research that used engineering principles, laboratorygrown tissue cells and computer extrapolations of what happened when those cells were subjected to loads, Gefen’s next question was how the knowledge could be applied to real-world situations. Working with Kopplin and with seating clinicians, Gefen decided next to focus on scar tissue, a too-common trait among wheelchair users.

Gefen and Kopplin referenced a sobering truth about pressure ulcers among wheelchair users: Once a client has one, it’s very difficult to prevent a recurrence.

“They never really heal,” Kopplin says. “We talk about healing from your pressure ulcer; that tissue’s never going to be the same.”

So seating professionals have to deal with the resulting scar tissue, which lacks the elasticity and load-bearing abilities of healthy skin and tissue.

Gefen contends that proper immersion and envelopment in wheelchair cushions — and specifically, his studies focused on ROHO air-celled cushions — are paramount to protecting wheelchair users not just against ischemic pressure ulcers, but also against deformation-inflicted DTIs. So a logical next step was to determine whether immersion and envelopment strategies would also work for clients who already have scar tissue — “different types and shapes and sizes of scars that clinicians see in the real world,” Gefen says. “We know based on work that is conducted in Japan, for example, that with simple ultrasound scanning, basically anatomical mapping, you can identify scars, even internally.”

This gives clinicians the chance to not only identify whether a client has a scar, but also its shape and size — and to judge the scar’s attributes not just by what’s visible on the skin surface, but also far underneath it.

“If the scar tissue goes deeper, it concentrates mechanical loads and acts as an additional site for mechanical stress concentrations, much like the bone,” Gefen says. “So we decided we wanted to look at the different scar shapes, scar sizes and locations.”

Borrowing the names coined by Japanese researchers, Gefen says, “SW is sandwich, because [such a scar] has components on the surface and components internally, just like a sandwich. Hourglass (HG) is shaped like an hourglass.” In the cross-section diagram , you can see the whitish shape of the IT, the gluteus muscle directly around the IT, the surrounding fat (yellow) and the scar tissue (blue). In some cases (i.e., “Thin”), the scar tissue is on the surface of the skin. In the SW illustration, scar tissue is present near the IT as well as on the skin. In the HG example, scar tissue is present from the IT all the way through tissue layers to the skin, creating a column-like structure.

The next part of the series will discuss how different scars react differently to loads, how cushions react to those loads, and the importance of adjustability in the wheelchair seat cushion efficacy equation.