Last time, I reviewed some
clinical aspects of amyotrophic
lateral sclerosis (ALS) and their
implications for power mobility.
ALS power chairs are unique in that
they must not only address a user’s
needs at a given point in time; they
must also address many foreseeable
issues we can expect to encounter
in the future. Their configuration
should provide an infrastructure
that allows them to be adapted
to changing needs, and we need modular solutions to address
those needs with less time, labor and technical expertise than is
currently the case.
Oftentimes, our big-picture success depends on our execution
of the individual details. If we use assessment, rather than
assumption, to determine how effectively a product meets a
given set of needs, we may find that relatively minor changes can
make a big difference. Open Complex Rehab is about analyzing
practice-based evidence, sharing what we find with others, and
improving CRT through mutual collaboration.
Head Positioning Possibilities
If we measure an outcome in terms of an ALS power chair’s
ability to meaningfully contribute to the user’s quality of life
throughout the disease, we will find that the headrest plays an
important role. Unfortunately, the industry’s approach to headrests
and head arrays can limit what may be possible for an end
user who has ALS.
If we want to encourage users to mitigate the adverse effects of
gravity by tilting their seating systems, a comfortable headrest is
essential. Still, we often sacrifice comfort when the headrest needs
to achieve multiple clinical objectives.
We know that axial weakness will eventually progress to a point
where the user will have difficulty holding his/her head erect
against gravity. If this weakness is not symmetrical, there may be
a tendency for the head to deviate laterally toward one side. With
early detection, a simple lateral spot pad may remedy the problem.
If allowed to continue unaddressed, it may become a significant
problem that could become impossible to correct. The greater the
progression, the greater the impact on the person’s quality of life.
In most cases, we do not know if asymmetry will be a problem at
the time we prescribe an ALS power chair.
Similarly, most users with ALS will not initially need switches on
their headrests. However, a significant number may benefit later on
as they lose anti-gravity movement.
When we prescribe conventional head arrays that have sensors
embedded in a firm occipital pad, we are sacrificing a certain level
of comfort to provide mobility.
With many of today’s products, the original hardware provided
with the chair may need to be replaced in order to use positioning
components or switches later on. A head array that can no longer
be used for driving is often a poor substitute for a comfortable
headrest, and its hardware may be significantly different. Too often,
this need to replace rather than upgrade results in missed opportunities
to have a positive effect on the long-term outcome.
We have tended to think of headrests that provide comfort, headrests
that provide positioning, and head arrays as distinctly different
products. In practice, I am finding that a significant number of
users would benefit from characteristics of all three. Some would
benefit from multiple characteristics simultaneously, while others
require different characteristics at different stages of the disease.
Users with ALS would benefit from a modular headrest that is
comfortable and provides enough positioning to address mild
asymmetry. It should allow us to build on what’s already there and
address emerging problems at the same time we identify them. It
should be possible to convert it into a driving control, or convert it
back to a headrest that provides switch access.
What’s Possible Now
While this may be a new way of conceptualizing the headrest, we
do not have to wait for new products to be able to implement
the concept. A 6″x4″ occipital pad combined
with two vertically
oriented 4″x2″ spot pads
has roughly the same
surface area as a 10″ headrest, but provides
lateral or suboccipital
support. As importantly, it includes the infrastructure needed to address the more-challenging
issues that may arise in the future.
For years I’ve been looking for better ways to mount switches on
headrests. Current mounting hardware is either too rigid to accommodate
minor variations in positioning or too flexible to provide
efficient activation. Those who need these types of products need
solutions that provide enough rigidity for efficient activation with
a very limited amount of adjustability for precise placement. To
appreciate how these characteristics have been effectively implemented
in a mainstream product, one needs to look no further
than the rearview mirror in a car.
Recently, I have been fabricating custom switch mounts using
1/4″ stainless steel tubing, modular hose, a CNC ball socket adapter,
and a flattened Loc-Line end cap. The assembly can be used in the
standard Stealth ball, shaped by hand, and provides enough finetuning
to position the switch for optimal efficiency.
Another issue with
today’s products is
they provide very little
support for the movements
used to activate
the switch. To understand
of this, let’s return to
our analogy about cars.
When we use the brake
pedal, do we lift our
foot off the floor and
move our entire leg
over, or do we keep our foot on the floor and rotate? Let’s refer to
the former as “lifting and shifting.” One movement does the lifting
to overcome gravity (hip flexion), while a second movement shifts
everything laterally (hip adduction).
Very few people drive like this because it takes a considerable
amount of effort. Human factors engineers design cars so the
location of the pedals allows most drivers to use hip rotation while
the heel stays on the floorboard for stability. Instead of “lifting and
shifting,” most drivers are able to use “rotation with stabilization.”
While we may take this for granted, a 1″ to 2″ difference in pedal
placement is all that would be required for our daily commute in
stop-and-go traffic to turn into a major workout.
When providing a conventionally configured head array to
someone with ALS, don’t be surprised to find that “lifting and
shifting” is the technique used to get to the lateral sensors and
mode switch. While cervical rotation would be far more efficient,
they primarily use forward and lateral flexion of their neck.
Why? They may need to keep their head off the occipital sensor,
and their only other source of stability rotation comes from
surrounding neck muscles that are already working to stabilize
the head. This problem is most obvious when they try to activate
sensors or switches from a fully tilted position.
Combining an external source of support with the capability
to precisely position switches and sensors within range is the key
to implementing “rotation with stabilization” in a head-activated
system. If this sounds very abstract and theoretical, one should
look no further than the picture below to see this concept implemented
in clinical practice.
So, are the things I’ve
discussed merely “technical
details” of interest
to a few motivated ATPs,
or are they important
clinical concepts that
would make future
products more effective?
As I mentioned,
sometimes our big-picture
success depends on the execution of individual details.
In my final installment, I’ll demonstrate how all these details and
concepts can be implemented in a way that can make a difference
in ALS outcomes. The topic will be “Hybrid Alternative Driving
Systems.” Never heard of them? Trust me, they’re very cool!
Editor’s Note: Steve Mitchell works at the Cleveland VA Medical Center. His opinions
do not represent official policy or positions of the Department of Veterans Affairs.