ATP Series

Staying Svelte

• By Laurie Watanabe
• Oct 01, 2014

In a uniformly accessible world, clinicians, ATPs and consumers wouldn’t have to judge a power or manual wheelchair based on size. Doorways would be wide enough, kitchen tables high enough and elevators roomy enough to accommodate chairs and consumers of all sizes.

But in the real world, size matters. That means you’ve also got to consider how well a wheelchair will fit into multiple client environments — most of which have not been built with wheeled mobility in mind — while simultaneously answering your client’s clinical needs.

Why a Chair’s Footprint Is Important

“The smaller the wheelchair base, the more maneuverable it will be in various environments,” says Amy Morgan, PT, ATP, national clinical education manager for Permobil. “These can include home, work, school, vehicle, public transportation, etc.”

Even a singular environment, such as the client’s home, can offer multiple types of accessibility challenges, says Mark E. Smith, public relations & outreach manager for Quantum Rehab.

“Bathrooms are a great example of why compactness is so important,” he explains, “Firstly, bathroom doorways are historically narrower than all others, sometimes as narrow as 28". It’s not hard to exceed that on a wide power chair or an ultralight with camber, so keeping a wheelchair’s overall width as narrow as possible is vital for doorway access. Secondly, bathrooms are typically confined spaces, so a wheelchair with a compact footprint and tight turning radius can make an otherwise inaccessible space accessible.”

Jill Kolczynski, manager of product development, powered seating & positioning for Invacare Corp., adds that the need for accessibility extends to how the wheelchair works with other medical equipment.

“Often forgotten is the ‘other’ DME taking up space in that home the user must accommodate with mobility — beds, lift s/slings, portable commodes, respiratory DME, etc.,” she says. “A chair that is too wide may not be able to turn in a narrow hallway and pass through a narrow bathroom door. One with a long footplate or footplates that can’t be moved out of the way by the consumer could put someone too far from the commode to transfer or from the sink to do dishes.”

At the same time, Morgan cautions against simply believing that a smaller chair is always the answer.

“When a wheelchair base is too small or compact, it can have issues with stability and this can potentially be problematic for the user as well,” she notes. “So smaller is not always better — even in manual wheelchair applications! There are always pros and cons.”

How Is a Footprint Measured?

The first step toward creating a wheeled mobility system that is functionally compatible with its environments is understanding what factors determine that compatibility. And while compact footprints are often discussed in conjunction with power chairs, this understanding also applies to manual chairs.

Jim Black, TiLite director of western sales operations, says, “The smallest possible footprint and turning radius are critical for the daily function of chair users. When chairs are wider or longer, they are more likely to interfere with a variety of activities of daily living that take place in space-constrained environments. That’s all really simple to understand — the problem is, and what we really need to be talking about, is what determines chair footprint. Most people assume that it is frame length. It is not.

“The misconception is that a smaller frame length will result in a smaller footprint and turning radius for the chair. This is not the case. Frame length is just one of several factors that impact the overall footprint of the chair and its turning radius.”

Black says it’s instead important to note three different influences:

1. Frame Length: The measurement from the front to the back of a wheelchair’s frame.
2. Center of Gravity (CoG) fore & aft adjustment: The measurement from the front of the back rest tubes to the centerline of the rear wheel axle.
3. Rear Wheels: This measurement again relates to the CoG adjustment, but for this exercise it’s the measurement to the back of the wheels.

“These three factors determine the overall footprint, and it’s the overall footprint that affects turning radius,” Black explains. “The overall footprint is the measurement from the front to the back of a completely configured wheelchair with the user sitting in it. The furthest back point is generally the back of the rear wheels — or sometimes components such as anti-tips might extend past the rear wheels. The furthest front point may be the end of the frame, the user’s feet or another component on the front of the chair, whichever sticks out the farthest. By assessing overall footprint, we can best approach how to give wheelchair users the smallest chair footprint and turning radius possible while maximizing their efficiency and function in all areas.”

Creating a Compact Footprint: Power

Achieving a compact footprint for a power chair requires looking at a number of different areas, Smith says — and keeping all measurements in mind.

“Complex rehab power bases,” he notes, “are typically a fixed width between 24" and 25.5". However, the width that seating and components add shouldn’t be overlooked. A power chair’s overall seat width is oft en the seat pan width plus 4" to 6" for the armrests and hand control. For example, a 24"-wide power base with a 20" seat width may have an ultimate overall width of 26" because of the added width of the armrest and hand control. In this way, the seating system’s overall width should be considered in addition to the power base’s width.”

Therefore, examining those other components could help to maintain a compact footprint.

“Among the best ways to narrow a power chair is to ensure that any protruding components — such as the armrests and hand control — are drawn in as close as possible,” Smith suggests. “Drop-in armrests are drawn in closer than flip-back armrests, so drop-in arms are one narrowing option. On flip-back armrests, using inset, endomorph back canes when applicable to the client can draw the armrests inward 2" to 4", reducing the seating’s overall width. Similarly, bringing the hand control inline, so it doesn’t protrude, can reduce overall width.”

Accommodating the power chair user’s lower extremities can be another challenge to maintaining a small footprint.

“One area that is commonly overlooked is the distance the footplates are from the front of the seat pan,” Kolczynski says. “Each inch farther out is an inch farther the individual is from the object they are trying to reach or surface they are transferring to unless they can move the foot rigging out of the way. Use of a center-mounted foot rigging can often help resolve this issue, as it pulls the feet in tighter to the base. Shorter foot plates can pull this in even further.”

Kolczynski adds that there can be trade-offs to that type of foot rigging: “Low ground clearance may require taller individuals to raise their seat-to-floor height or tilt while driving to get adequate distance to navigate obstacles outdoors. Some users are not able to sit with their feet close to midline on the footplate. Legrests that they can swing out of the way easily may also be a solution, as long as they have room to swing and they are light enough for the consumer to be able to perform this function independently.”

While power chair width likely comes to mind first when dealing with environmental accessibility, Morgan points out that seat-to-floor is another critical measure — not just for fitting under tables and desks, but also when boarding automotive vehicles.

“It can be very deceptive at times, when adding power seat functions — they will add significant seat-to-floor height,” she notes. “This is something to always be cautious about and ask how seat-to-floor height will change with the addition of seat functions. Sometimes, seat functions like anterior tilt can help lower someone’s front seat-to-floor height for improved environmental access. Another perspective with powered seating is using recline for postural stability under tables, driving consoles, etc., instead of tilt to keep the knees lower and allow clearance.”

In some cases, Morgan points out, the wheelchair user’s lower extremities can limit how low the seat-to-floor height can be.

“The biggest limitation to getting a seat-to-floor height low enough is the user’s lower leg length. With longer lower-leg lengths, adjustments or compromises have to be made to keep the footplates from hitting the ground and allow appropriate ground clearance. In some situations, the leg rests can be elevated to achieve lower leg length; however, this will lengthen the overall footprint of the chair and may cause maneuverability issues. In other cases — more with manual wheelchairs — the user’s feet can be tucked under the seat to accommodate a long lower-leg length.”

Creating a Compact Footprint: Manual

Much of the “footprint” discussion traditionally focuses on power chairs — but there are also considerable benefits to keeping an ultralightweight manual chair’s footprint more compact.

Linda Zettergren-Sopko, business manager for active/medium-active wheelchairs for Invacare Corp., says, “A smaller footprint chair will allow the consumer to be more compatible with obstacles encountered in daily living. When the wheelchair is more compact, it will likely weigh less and allow the consumer more flexibility to transfer, transport and reduce stress on lift ing and energy used to propel the wheelchair.”

Zettergren-Sopko suggests checking out not only the wheelchair itself, but also the components added to the basic frame.

“It is also important to consider options or ‘add-on’ products that some wheelchairs offer to help navigate through occupied space,” she notes. “If push handles are needed, or armrests, consider fold-down designs, which allow them to be secured out of the way, and removable armrests that can be moved out of the way, if needed, to allow better access. Low-profile handrims and front casters are another good suggestion, as well as a flip-up footplate that can help the consumer get into even more spaces that could be limited if the footplate bar is solid and cannot be moved out of the way.”

Alan Ludovici, senior project engineer for Ki Mobility, says an ultralight’s frame can have a surprisingly significant impact on the chair’s overall footprint.

“When a chair’s frame lacks stiffness and the wheels flex, especially when turning, the wheels can ultimately rub against the frame,” he explains. “The result is the chair’s design requires more spacing between the wheel and the frame to accommodate for the natural flex in the system, requiring — you guessed it — a wider chair. The stiffer the frame, the stiffer the wheel, the narrower the chair can be made.”

That holds true for folding ultralights as well, Ludovici adds, noting that Ki’s cross-brace design “makes the frame extremely stiff. The result is our system naturally allows the wheels to be mounted quite close to the side frame.”

And while weight is not technically part of wheelchair’s physical footprint, it’s an inescapable factor when judging how well the chair fits into its user’s routine and makes environments more accessible.

“Many consumers, and clinicians, still consider weight to be the primary requirement of a wheelchair,” Ludovici acknowledges. “Today, there are so many chair options available in the market around 16 lbs. that we need to start looking beyond just weight.”

He cites a chair’s propulsion efficiency and ride quality, but also suggests examining the chair’s ease of use: “Do the armrests and wheel locks work for the user? Can they get close to things? Can they transfer from the chair, and how easily can they get it in and out of their car? With weight already addressed, we now have the opportunity to pay more attention to these essential factors.”

Black agrees that weight is still top of mind for many ultralight users.

“The consumer will always have this concern,” he says, “and we as consumers will always want the lightest transfer weight possible. The simple answer here is to know where weight comes from when transferring a wheelchair into the vehicle. A lot of the weight is not primarily from the frame, but the components and the adjustment added to the frame. I believe as our industry matures, our components and adjustments will get lighter and more advanced, reducing the transfer weight of all products. One critical component in this is the effort to improve the compactness of the products, because that effort requires more moving parts, which creates a dilemma/conflict when also trying to keep the chair light and durable.”

Customized Solutions for Unique Situations

As with any complex rehab technology solution, a wheeled mobility system’s ultimate success can come down to the adjustments that ATPs and clinicians make to fine-tune the wheelchair to its particular user.

“The position of the rear axle (CoG adjustment) must be configured around the user in order to achieve minimal chair footprint and turning radius, and maximal user functionality,” Black says. “CoG should never be used to ‘fix’ problems like instability! We give ourselves the ability to correctly configure the CoG by correctly choosing a frame length proportional to the user’s body during the fitting process — once the chair is built and being set up for the user, it is too late to correct this!”

By properly fitting the chair’s frame to the user, Black explains, “We are able to maintain overall footprint and turning radius while maximizing the user’s own efficiency and comfort. It is only from understanding overall footprint that we can understand how creating what may be a longer frame length can and will result in the smallest possible chair footprint and turning radius while maximizing functionality.”

Zettergren-Sopko says it’s important to be able to match the user’s lifestyle with his or her ultralight’s configuration.

“If the consumer is independent and very active, their lifestyle will warrant the need of a compact, yet comfortable wheelchair that is maneuverable in tight spaces,” she says. “A properly fitted and designed ultralight rigid custom manual chair will exhibit traits making the consumer feeling ‘at one’ with the wheelchair.”

Knowing an individual user’s personal habits, strengths and challenges can also help the seating & mobility team select complementary components.

“One of the biggest culprits of weight is wheels,” Ludovici says. “Using lighter-weight wheels and pneumatic performance tires can quickly shave pounds off overall chair weight and not necessarily make you more susceptible to flats. The chair will be noticeably easier to transfer in and out of a car and will be so much easier to push.

“It is also important to consider the distribution of weight across a chair, especially when transferring. For example, heavier front casters make a chair difficult to transfer into a vehicle because the weight is so far away from your body, making it that much harder to lift .”

On the power side, knowing that client’s preferences is just as important. For instance, regarding seat-to-floor height, Morgan says, “The lower the seat-to-floor height, the more stable the chair — which is a good thing! But from a ‘social’ aspect, lower seats require that the user is constantly looking up more at others who are standing. This might put extra stress on neck muscles and potentially cause pain/headaches. It is optimal to be able to adjust seat-to-floor height — like by using a seat elevator — so the user can be low when needed and can also have eye-to-eye interactions with the standing world.”

Other environmental or clinical needs can also help to determine the power base size that works best for a particular client.

“Sometimes a larger power base is beneficial,” Smith says. “For wider seating and higher weight capacity, a wider, longer power base is an ideal platform. Ventilator-ready power bases also benefit from a larger footprint, best supporting the increased weight and shifted center of gravity. And for higher-speed power chairs, a wider, longer wheelbase can improve tracking, handling and stability.”

Morgan agrees that a smaller base isn’t automatically the right answer in every situation.

“Many times, manufacturers will compromise with battery size when trying to keep the wheelchair base smaller and compact,” she notes. “At times, this is OK to do and won’t create problems for part-time users or less active people. However, it is important to have sufficient battery capacity for active users so they do not get stranded when they are out or have poor battery performance.”

Changing a power chair’s center of gravity can help to keep the chair more compact, especially for certain types of clients, but ATPs and clinicians need to do so carefully, Kolczynski says.

“Adjusting the center of gravity of a seating system relative to the base can sometimes make the base more compact by shortening the distance from the center of the drive axis to the footplate,” she notes. “This is something that needs to be done carefully to ensure the chair remains stable aft er the adjustments. Adjusting too far rearward, especially with a client who carries their weight farther back like an amputee, can make the chair rear tippy. Similarly, adjusting too far forward can make the chair front tippy.”

Finally, Morgan says, no matter which configuration the seating & mobility team chooses, and no matter what fine-tuning is done, good client training is mandatory for a good result.

“While turning radius typically is the main consideration for maneuverability, the wheelchair setup and client instruction in its use is equally important,” she says. “A great example is front-wheel-drive power wheelchairs — or manual wheelchairs in ‘reverse’ configuration. When turning around corners, these chairs can ‘hug the corner’ and make tighter turns than their mid-wheel-drive counterparts with the ‘smallest turning radius.’ The critical component is making sure that the client knows how to utilize their drive wheel configuration optimally.”

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