Page 21 - Mobility Management, May 2018

in a centered position — isn’t necessarily an accurate picture
of how the cushion will be used in the real world. During daily activities, consumers lean from side to side while reaching
or doing weight shifts. Their bodies move as consumers self propel, as they tilt and recline, as they transfer from their chairs into bed. All of this movement impacts the shape the cushion assumes, how weight is distributed in and across it, and even how the cushion’s cover interacts with the client.
So how do manufacturers design cushions that do their jobs when clients are sitting still and while they’re moving?
Anthropometrics & Design
There is a range of seating possibilities for these clients, Cwiertnia said.
“[One] extreme would be a custom-contoured cushion that
is uniquely designed for an individual and often functions to prevent progressive deformity or abnormal tone,” she explained. “These cushions can limit activities if the client engages in activi- ties that the cushion was not designed for.”
Most CRT clients use less-customized products — cushions that have skin protection and/or positioning features, but are still designed to fit a range of consumers rather than a particular individual.
“When designing ‘off-the-shelf’ cushions that have contours or features that are dependent on anatomy, the engineers try to incorporate anthropometrics, which is scientific information about humans’ sizes and shapes,” Cwiertnia said. “Since the ‘average’ human doesn’t exist, the engineers have to determine a range above and below the average that they want to accommo- date. The goal is to develop a shape that will work for a majority of clients, but may not work for everyone.”
“Unfortunately, we don’t have the tools to see how a person
is sitting all day long,” Sayre said. “But what we’ve done is work with anthropometric measurements. We know that, for instance, in an adult pelvis, the ITs [ischial tuberosities] are normally spaced anywhere from 4.5" to 5" wide. You go with that as your foundation.”
Of course, for every client who fits within that “average” range, ATPs and clinicians can point out a client who doesn’t.
“I’ve measured some ITs that are 7" across,” Sayre recalled. “So you have to make accommodations for that. Normally, you make the [cushion] well oversized, because for instance, if the person goes into tilt, we have no problem. But if the person goes into recline, and then they tilt and you open up that hip angle, you
are going to have some shearing and movement. So you make that well a little bit bigger to accommodate [their position]. You figure out how much you want that person to move.”
There are also anthropometric differences between male
and female users. “When you look at the adult pelvis, there are gender differences,” Sayre said. “With the male pelvis, the ITs are a little bit closer than a female’s, because a female’s was designed to have children. So female pelvic girdles are a little bit wider, and those ITs are a little bit wider versus a male’s.”
Sayre said that during evaluations, she has observed how movement can change the client’s position on the cushion.
“I would have them lean forward and have them go into recline or tilt, because if the well is too small, their ITs might shear
and hit the edge. Sometimes I would chamfer the edge off [the cushion] if I could get to it. Sometimes the top layer of the visco [foam] is glued and you can’t get to it. Then you have to choose a different cushion.”
Cover Story
Cushion covers are affected when clients move — but covers can also impact movement in return.
“Cushion covers are often an integral part of the cushion design and function specifically to that cushion,” Cwiertnia pointed out. “Covers can provide protection to the cushion from daily exposure to dirt, moisture, UV exposure, and physical wear. Some covers are designed to assist with the breathability
of the cushion, pressure management, moisture management, friction and even for flammability and anti-microbial protection.”
Cover properties can vary according to their construction, Sayre noted.
“For instance, mesh is not only used for air flow, but some people like it because it’s a little more abrasive than Lycra or nylon,” she said. “Some people use it to keep themselves in place, because otherwise, they could slide all over the cushion.
“[Mesh] acts as a stabilizer. For some people, if they’re active and able to get in and out [of the chair], mesh keeps them from fatiguing as much. It keeps them upright. For instance, I know a gentleman with a C5-C6 [spinal cord injury], and he will not use anything but mesh because it keeps him stable. It keeps him in place. Some people put mesh on the backrest.”
Just as some consumers prefer the more tacky texture of mesh to help them stay in place, others prefer a smoother surface with less resistance because such a cover can facilitate transfers.
“For CoolCore,” Sayre said, referring to Stealth’s cushion cover
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