Wheelchair Seating: The Mat Assessment

Wheelchair Seating: The Mat Assessment
Michelle Lange, OTR, ABDA, ATP/SMS
March 23, 2019

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Key Components

Here are the key components of a mat exam that we need to include. 

  • Muscle Tone
  • Muscle Strength
  • Range of Motion
  • Reflexes
  • Movement patterns
  • Postural Control

We need to look at muscle tone for the client, muscle strength, range of motion, reflexes. particularly those primitive reflexes and how they might be impacting someone's body position, movement patterns that we see within that client and overall postural control. If there is not a lot of postural control then we need to recommend that support to accommodate that.

Mat Exam Documentation

Once we have a client on that mat table, we need to describe what reflexes we are seeing and the influence of those on body movement and posture. That becomes part of our documentation, and it determines how the seating system needs to be set up to meet those needs. We need to describe muscle tone, whether it is high, low, or a mixed presentation. A lot of my clients have very low tone in the trunk and the neck, but they might have high tone in the extremities. I need to describe how that influences their body movements and their posture. For example, if there is high tone in the legs, I might see a lot of extension in the hips, knees, and ankles. If there is low tone in the trunk, I might see some posterior pelvic tilt and trunk kyphosis as the client collapses against gravity. I need to note any range of motion limitations particularly those that are going to impact seating. We will go through range in a little more detail here in a moment, but I do not document every single range joint that my client has. I, instead, focus on those that are impacting seating like the hips and the knees. I also want to note any orthopedic asymmetries. Perhaps, there is a non-reducible spinal curvature that we need to accommodate or correct.

As we are performing a mat exam, it is important to look for causes, not just symptoms because of the justifications for what we are recommending address those causes. For example, if I note that this client has poor trunk control, I need to figure out why and what do I need to recommend to support that. Let's say somebody has some of that trunk kyphosis due to weak trunk muscles. I need to document that, and then document my solution. Our documentation needs to include our observations, the problems we are seeing and possible causes, and any recommended solutions. Depending on the cause, our solution is going to be different.

Importance of Mat Exam

If you do not have a mat table available, you might think, "I can just evaluate them in their wheelchair." Well, it is important to look at the client in their wheelchair seating system. In fact, I will take pictures from multiple directions particularly front and side to document the client's sitting. I will include that in my letter of medical necessity. However, I still need to get the client out of the wheelchair and on to a mat table in order to eliminate gravity. Gravity is not always our friend. By getting rid of the influence of gravity, we get a better sense of this person's range of motion and control. Also by removing the support that the client is currently receiving in sitting, even if it is inadequate support, it is clearer to see what is truly going on with this client and what their true support needs are.

It is also tempting to use a bed. The problem is that the surface of the bed is too soft for this type of assessment. When looking at available hip flexion, this measurement may be skewed if the pelvis is pushing into the soft surface of the mattress. We need to use a less forgiving surface to do a more accurate evaluation.

Let's now talk about some specific components, things that we want to measure during our evaluation.

Muscle Tone

  • Muscle tone can be measured in several ways
  • Why do we measure this?
  • Muscle tone can “pull” the body into undesirable postures and impair function
  • Certain seated postures can inhibit or “break up” tone

First is muscle tone. Now there are a number of different ways we can measure muscle tone, and there are many different tools that are out there. Muscle tone can pull the body into undesirable postures and impair function. If someone has more tone on one side of their trunk than the other, it is going to shorten that side for the client that will impact spinal position and where support is needed. During the mat assessment, we can determine if certain seated postures can inhibit or "break up" that tone. We know that for people who have increased muscle tone, there are certain strategies we can use that help inhibit some of that tone. We can play with those postures on the mat, and then decide how to apply that within the seating system. For example, most people who have increased muscle tone, particularly extension, can be better positioned by adding in some flexion at the hips, knees, and ankles. A little hip abduction can also help to inhibit extensor tone.

When I am working with the client who needs to complex wheelchair seating system, I often recommend a new wheelchair for them and maybe other equipment. It takes a long time to do this evaluation. Thus, I do not always use a formal muscle tone assessment. I will simply note what I am observing. For example, I might note low tone in one area and high tone in another. I could note velocity-dependent tone that is characteristic of people with cerebral palsy. I could also write a fluctuating tone in my documentation. If you feel that you do need a more formal assessment, you can use the Modified Ashworth Scale. It is probably the most common tool that we have for measuring muscle tone.

Muscle Strength

  • Muscle strength can be measured in several ways, as well
  • Why?
  • Impaired strength may be a justification for an ultralight MWC, power assist wheels or a PWC
  • Impacts ability to self propel, sometimes more so over distance or varied terrain
  • Cardiovascular status, as well

Muscle strength impacts seating in terms of having adequate strength to maintain an upright posture. Muscle strength also comes into play when choosing a mobility base and justifying that mobility base. If someone does not have adequate strength to propel a more standard or lightweight manual wheelchair, then this might be justification for an ultralight manual wheelchair, for power assist wheels, or even for a power wheelchair. It is important to document strength in the documentation as it impacts not only the ability to self propel, but it limited self-propulsion over rough terrain or longer distances. Along with that, we need to keep strength in mind for the person's cardiovascular abilities as well. This activity might be more than this person can tolerate. Again, I do not typically do a formal strength assessment as a part of my recommendations, but occasionally, this may be required by some funding sources. 

Range of Motion

  • It can take a long time to do a full ROM exam
  • Usually only necessary to look at key areas
  • Can the pelvis be placed at neutral without spinal movement?
  • Are there any fixed ROM losses? Spinal or pelvic asymmetries?
  • Can the knees be extended without posterior pelvic tilt? How far?

It takes a really long time to do a full range of motion exam. Usually, it is only necessary to check out a few main areas. We are going to go into this in more detail as we talk about the actual mat assessment in supine and in sitting. Some of these key areas are ensuring that the pelvis can be placed in a neutral position without causing movement of the spine. This is something that has to be looked at very carefully. It can be easy to miss. Sometimes we think there is full hip flexion and do not realize that we are really driving the pelvis back in a posterior tilt. I also note if there are any fixed range of motion losses that are going to impact seating as well. If someone has a curvature of the spine or maybe a fixed or non-reducible pelvic asymmetry like pelvic obliquity that I cannot correct, then I need to make note of that because that has to be accommodated within the seating system. Once I have the pelvis in a neutral position as possible, I need to extend their knees without pulling the pelvis into that posterior tilt. The hamstrings are attached to the knees thus their flexibility also dictates pelvic position.

Postural Control

  • Always examine the client in supine and sitting at the edge of the mat
  • Why?
  • Supine eliminates gravity so you can check range, tone, strength, and alignment without gravitation forces
  • Sitting allows the evaluator to start “simulating” angles and support surfaces
    • What you can support with your hand, can be accomplished in a seating system

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michelle lange

Michelle Lange, OTR, ABDA, ATP/SMS

Michelle is an occupational therapist with over 30 years of experience and has been in private practice, Access to Independence, for over 10 years. She is a well-respected lecturer, both nationally and internationally and has authored numerous texts, chapters, and articles. She is the co-editor of Seating and Wheeled Mobility: a clinical resource guide, editor of Fundamentals in Assistive Technology, 4th ed., NRRTS Continuing Education Curriculum Coordinator and Clinical Editor of NRRTS Directions magazine. Michelle is a RESNA Fellow and member of the Clinician Task Force. Michelle is a certified ATP, certified SMS and is a Senior Disability Analyst of the ABDA. 

 



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