Width + Depth + Height

Width + Depth + HeightIt’s simple: When building a seating system, measure the client to determine how wide and deep the wheelchair seat should be. Backrest height can be determined by the client’s stability and personal preferences. Get those three measurements — width + depth + height — and you’re ready to go.


Of course, in the real world, it’s not that easy. A number of factors, some clinical and some environmental, can influence how wide and deep a seat should be for a particular client, and how high the backrest should be.

Once funding sources chime in, the noise level rises. With their insistence on product longevity, reluctance to pay for replacements, and shrinking budgets, payors can seem to have the loudest voices of all.

So how can ATPs and seating clinicians work so that clinical, functional and funding concerns are all diligently addressed?

Why Seat Size Matters

To a world accustomed to standard-sized hospital wheelchairs, being so meticulous about seat width and depth as well as backrest height may seem strange. Why are exacting measurements so critical to functional success?

Generally speaking, clinicians advocate for wheelchairs with small footprints, which directly correlate to the size of the wheelchairs’ seating systems.

Tricia Garven, PT, ATP, clinical applications manager for ROHO Inc., notes two main advantages of a smaller footprint — and thus of a properly sized seating system.

“First of all, shoulder-to-wheel alignment for shoulder preservation,” she explains. “If your arms aren’t having to reach out to the wheels, then you’re going to be set up for more success in terms of less pain and better alignment.

“But then also there are accessibility issues in the environment — getting through doorways, turning around in restaurants — because the wider your chair is, the bigger your turning space is. Being in crowded places, getting into bathroom stalls — the handicapped stall isn’t always there or available.”

A seating system that fi ts properly is especially important to the consumer who self propels, Garven says.

“You don’t want them to have to bend their elbows outward,” she explains. “Of course they’re going to be bending their elbows to push, but you don’t want them to be reaching out, opening up the armpit.”

The same goes for pediatric wheelchair users, says Lauren Rosen, PT, MPT, MSMS, ATP/SMS, program coordinator, Motion Analysis Center, St. Joseph’s Children’s Hospital of Tampa (Fla.).

“If you’ve got a kid who is a manual chair user and the chair is too wide — the [smallest children] already have trouble reaching the wheels and handrims as it is. Imagine the handrims even further out by making the chair too wide, and they can barely touch the wheel itself.

“Also just by doing that, you’re pre-disposing those kids to shoulder problems because the research tells us the more you abduct your shoulders, the more damage you can do from propulsion.”

Children who use power chairs can also run into access problems if their seats are wider than necessary.

“You can’t reach to the joystick, you can’t reach to the armrest,” Rosen notes. “If the chair is too wide, you can’t reach everything. In some cases, we will make the power chair a little bit wider than we would a manual chair and just put a bunch of hip guides up against the kid, but they’re still reaching for the joystick, which makes it more difficult to operate the chair.”

And that difficulty could be costly to a child trying to demonstrate that he or she could indeed be a successful power chair operator.

“With all of the things coming out about what somebody should be capable of doing before qualifying for a chair — if you put the joystick farther away, any of us would have a harder time of navigating successfully through a maze or cones or whatever,” Rosen says. “It just makes it harder to control the chair if you’re having to reach too far.”

As for determining how deep the seat should be, Rosen says, “If you choose a seat depth that’s too large, you end up with a kid who has to slide forward, so they sit with a posterior pelvic tilt. You’ve got the problem too that a lot of the kids who use wheelchairs are kids with cerebral palsy who have spasticity, so most of those kids have really tight hamstrings. And so they’re already needing to tuck their feet underneath them as much as they can; that alone is causing them to sit with a posterior pelvic tilt. You add a too-deep seat depth, and you’ve got a kid who’s kind of lying down.”

Regarding how high a back should be, Garven says, “You want backrest height to be as much support as necessary without being too much. Too much back height, too much anything in the back, is probably going to limit upper-extremity movement, and it may even hinder their ability to have small corrections with what balance they do have if that backrest is too high. It might not allow as much movement as they personally have.”

Rosen says the thought process is much the same for kids.

“If it’s a kid who has good trunk [control], I’ll do the backrest just like I would do with an adult and try to go right below the scapula,” she says. “If I’ve got a kid with [less trunk control], then we’ll cheat a little bit higher. I try to never go [up to] the shoulder height. I try to always stay at least an inch or two lower, even in those kids. The kids who have really bad trunk control will end up with a solid back and laterals, so those tend to be a little bit taller to give you more support and room.

“I don’t want the back getting in the way of propulsion. It’s the same as with an adult: If my scapula can’t move like it needs to move, I can’t propel nicely, I can’t do everything I need to do because I hit my chair every time I go to push.”

Sizing Up Tomorrow’s Measurements

If clients generally do better with seating that’s just right instead of too big, why not just build systems that fit clients exactly the way they are? In a word: time. Garven and Rosen both indicated that payor expectations force the seating team to make their best estimates in determining whether today’s “perfect size” will also work years into the future.

Garven notes that looking into the future can be particularly difficult for clients with new diagnoses who may need larger seat widths down the road — and possibly before funding sources are willing to buy new equipment.

“It’s a challenge, and that’s where the therapist interview with the client and family members, the whole healthcare team, is important,” she says. “When somebody’s fi rst injured, it’s tough. If somebody’s been injured for a long time, then it’s ‘What is your history? Have you been gaining five to 10 lbs. a year?’ Because we can probably expect that to continue unless they’re going to do something about it. If somebody says, ‘Yeah, I’ve been gaining weight, but I’m going to quit’ — you have to be realistic.”

Seating team members may have to dig deeper for information when the client is newly diagnosed.

“I think the real challenges are the clients who have gained or lost a ton of weight in the hospital,” Garven says. “You’re sort of guessing: Are you going to keep this weight, or are you going to lose some more? I know you have a spinal cord injury so you’re going to atrophy, but that doesn’t necessarily mean your belly’s going to get smaller.”

Understanding the client’s lifestyle before diagnosis, as well as their intentions post diagnosis, is also important.

“What do you expect, person in the wheelchair, to be doing in two to three years?” Garven asks. “What do you think you’re going to be doing?

“I think that’s also where the whole multi-disciplinary team becomes involved because especially if somebody is newly injured, you’re going to have access to probably neuropsychology, to nursing, to physicians. Everybody has conversations with this person, and they’re going to know — how is this guy coping? Because even the most active, fit person can become severely depressed, and that’s going to lead to sedentary, static behavior, eating, things like that.”

Anticipating Kids’ Growth

With children, from infancy right through their teens, the challenge can be in anticipating how much growth they’ll experience before they’re able to qualify for their next wheelchair or seating system.

“All the pediatric chairs have some kind of growth built into them,” Rosen says. “In the manual chairs, most of them have 2" or 3" of depth and 2" or so of width growth built into the system, where you just have to change out some parts and all that. If I’ve got to grow a chair during the five years, insurance is willing. Sometimes with older kids in manual chairs, if we do a rigid-frame chair, most manufacturers have a growth program where if you outgrow the frame, they will send you a new frame for cost, and it’s counted as growth, not as a whole new purchase.”

But the seating team must still determine the size of the initial system.

“The big thing that I’ve looked into is growth in kids with disabilities,” Rosen says. “Kids with disabilities don’t grow as fast — [not] at the same rate as able-bodied kids. The thought process is ‘They’re going to grow a ton in the next five years.’ Our kids don’t grow as much. They especially don’t tend to grow in width as much. In kids with cerebral palsy, their bodies are working so hard all the time that their metabolism is off the charts. So a lot of those kids don’t have as much of a tendency to gain a ton of width growth; they tend to grow in depth more. The measurement that seems to be the most off on kids is the width. Everybody is planning for a ton of growth that these kids just don’t have.”

As a general rule, Rosen says she asks ATPs to build in an inch of width growth for a pediatric self-propelled chair.

“For an adult chair, for somebody who propels, I tend to put it at the width the person is. But with kids, I will usually give them an inch, or if they’re a 10.5, we’ll go 12,” Rosen says.

“In power, I will probably give them 2" only because it’s not as critical. I’m not giving them more than 2". That’s the most I will give anybody, width wise, on a power chair. I don’t want them reaching, and I don’t want them to feel like they’re swimming in the chair.”

Rosen says her clients haven’t outgrown their chairs and seating systems, despite relatively conservative widths. And she has another reason to prescribe seating that’s not overly large: It can be a self-fulfilling prophecy.

“A lot of the kids I see around here are in ‘diagnosis seating’ — where every kid has the exact same chair and the chairs are too wide,” she says, adding that those clients are overweight, sometimes very significantly.

Noting friends who have spina bifida and who are in excellent physical condition as elite athletes, Rosen says, “I know that spina bifi da as a diagnosis does not lead to being fat. So I look at chair setups and how hard it is to push. For a kid, if everything is hard to push, do I want to go out and try to chase the other kids in the neighborhood who are running, or do I want to sit on the couch and eat the Cheetos?”

In that way, Rosen says, wheelchairs that are wider than they should be can cause vicious circles: propulsion problems that lead to sedentary lifestyles, weight gain and, yes, larger seating widths.

“If every day, everything about moving yourself around is difficult because your chair setup is bad, then we’re not encouraging kids to be active,” Rosen says. “We’re encouraging the couch and Cheetos. My idea of making the chair lighter weight and more dialed in to a kid is going to make them more functional and give them a better quality of life than doing the diagnosis seating where everybody gets the same chair.”

Finding the Sweet Spot

So how can ATPs and clinicians choose measurements that meet the needs of clients now and later as well as the long-term demands of payors?

Both Rosen and Garven take a “less is more” approach, in which they gather all the information they reasonably can, then try to dial in seating to create as compact an overall footprint as they can.

Referring to backrest heights, Garven says, “That one to me is a little bit more forgiving. The height on most of your chairs comes in ranges. Unless you’re dialing in a wheelchair and getting something that’s totally fixed, most new chairs have a back height range that you’re choosing. Also if you’re attaching a solid backrest, you have a little bit of play there, I’d say up to an inch or an inch and a half, or 2" depending on the height of the backrest because you can move it down. You just don’t want to move it up so high that you lose contact with the pelvis, which is what’s helping to create your positioning. And that’s how the backrest can support healthy skin and posture.”

As far as estimating seat depths and widths, Garven suggests getting opinions of other healthcare professionals working with the client — especially a newly diagnosed one — but also having an honest conversation with the client about his or her impact on the situation.

“I think patient education is important, too,” she says. “‘Look, I’m getting you this wheelchair because this is our expectation; don’t blow it. Don’t go home and eat only junk food. You need to eat healthy, and this is why: You’re not getting a new wheelchair for a long time.’

“There’s no benefit to not being honest and realistic with the funding challenges: ‘Understand how much this costs. Insurance is going to pay for it, but they’re not going to do this again quickly.’ [The client] can’t say they want a 15"-wide chair when they’re measuring 18" wide. But if you’re sort of bouncing between 18" and 19", or 18" and 17", having them be informed and having everybody involved and discussing it is going to be helpful.”

Rosen says she takes a look at her pediatric client’s family to estimate how much her client will grow. “If the family is a skinny family, chances are the kid’s going to stay skinny. There’s genetics involved in how we grow and what kids are going to look like, so I do look at the family and if siblings are there, I think about that. I’ll ask, ‘How tall is Dad?’ so we know what people’s propensity for growth is. If the entire family is 5’2”, a kid who’s not weight bearing most of the time isn’t going to be 6'10".”

Still, with every child, with every client, Rosen acknowledges the possibility that the improbable might happen.

“The biggest thing to making that determination is treating them like an individual and looking at everything,” she says, “Not just saying, ‘With every kid, I put in an inch of growth’ or ‘With every kid, I automatically do this or that.’ With seat depth, we’ll do their exact depth on the younger kids. With the older kids, we’d do closer to what we’d do with an adult and give them a little bit of room behind the leg.”

She adds that a well-fit chair, one that’s not too deep or too wide, has less tangible benefits, as well.

“I do believe that part of the reason for doing the chairs the way that I do them is so that you are seeing the kid and not the chair. I don’t have the medical necessity of that, but realistically the more you see the kid and less the chair, the more you see the kid as a person. There’s less of a stigma attached to having a chair.”

This article originally appeared in the Seating & Position Handbook 2014-2015 issue of Mobility Management.

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