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Our Family Is Crazy
Mike's Message

8.12.21
By: Mike Billings
Date: August 12, 2021

BIOMECHANICAL CONSIDERATIONS FOR WHEELCHAIR FOOT PROPULSION

By Mike Billings, PT, DHSc, MS, CEEAA

Last month I had an opportunity to tour the memory care unit of a retirement community that Infinity will begin serving soon. In me, the physical therapist immediately noticed many residents with poor wheelchair positioning and other conditions needing rehabilitation interventions. I do not consider myself a wheelchair seating expert. Still, it is one of my favorite practice areas because proper positioning can positively impact the quality of life of the older adults we serve.

As physical and occupational therapists, we are often called upon to prescribe wheelchair seating systems for our older adult clients. Sometimes, the objective is to improve positioning, prevent skin breakdown, or find an alternative to restraint use in the wheelchair. Frequently, though, it involves promoting mobility, which usually includes components of all the above.

One of the most common reasons for referral to therapy for a seating evaluation is the client’s problem of continually sliding out of the wheelchair. Though less common now, some wheelchair restraint devices may have already been tried without success. Yet, the client continues to demonstrate poor positioning, requiring frequent repositioning by the caregiver. Aside from restraint use being unacceptable in today’s nursing home environment, this type of solution fails because it is not specific to the client’s individual needs.

The only way to determine the valid reason for the apparent positioning problems is through a detailed assessment, including gathering background information from the medical chart and patient, family, and caregiver interviews, current equipment setup, environment, and a thorough evaluation on a therapy mat.

There are many factors to consider when determining a proper wheelchair setup. The most obvious is the height of the seat to achieve adequate heel strike. Most nursing homes are equipped with a fleet of standard sling-seat and sling-back wheelchairs that are eighteen inches wide, forcing the clinician to adapt it to the correct height. In addition, the client’s heel to knee length must equal the overall seat to floor height. A lower seat to floor height can be accomplished using smaller diameter rear wheels, castors, or a drop seat.

Seat height is only part of the solution. To complete the process, we have to refer to our evaluation findings and apply our knowledge of anatomy and kinesiology. The primary focus should be on the pelvis. Recall that when it tilts anteriorly, the lumbar spine goes into extension. When the pelvis tilts posteriorly, the lumbar spine goes into flexion. To keep the pelvis in the most functional position possible, we must also realize that it anchors many major muscles. For example, the extensors of the spine, iliopsoas, some hip adductors, and the rectus femoris muscles all act upon the pelvis to tilt it anteriorly. Conversely, the abdominal, hamstring, and gluteus maximus muscles act upon the pelvis to tilt it posteriorly.

To make the wheelchair move, the client must work against rolling resistance and create friction against the ground with the heel. This effort requires a tremendous amount of energy because standard wheelchairs can weigh as much as 50 pounds. Not only is it essential to get the feet on the ground, but also to observe their position. You can test this on yourself by placing your feet forward on the floor while sitting and pressing your heels straight down. The upper body tends to push back into the chair, while the hamstrings pull the pelvis into a posterior pelvic tilt and may even cause the pelvis to slide anteriorly in the chair.

Alternatively, when sitting in a 90-90-90 position and pressing the heels straight down, the upper body tends to move straight up. Now put your feet under the seat and push your toes straight down. The upper body tends to lean forward. This activity demonstrates how muscles connected to the pelvis act differently depending on where the foot puts pressure on the floor. If the resistance is great, these compensations become more pronounced.

These compensatory movements may also become noticeable when the wheelchair is inadequate. For example, suppose the seat is too high. In that case, the client tends to slide anteriorly in the chair and propels with the plantar flexors and hamstrings, which promotes even greater posterior pelvic tilt and anterior sliding. The client may also lean forward to compensate, thereby becoming at risk for falling out of the chair. Conversely, suppose the seat is too low. In that case, the distal thighs tend to rise off the seating surface, placing greater pressure on the ischial tuberosities. Or the client may slide anteriorly in the chair with the upper body pushing back into the chair.

Unfortunately, a common solution in nursing homes to sliding forward out of the wheelchair is to place a wedge cushion in the chair. The client then must fight harder to overcome the even greater floor to seat height or cannot accommodate the greater hip flexion that the wedge cushion causes and slides further anteriorly in the chair.

So what adjustments should be made? Since forward propulsion promotes flexion of the spine, posterior pelvic tilt, and anterior migration of the pelvis towards the front of the chair, a contoured cushion can be used to stabilize the pelvis and keep it centered in the back of the chair. In addition, a solid horizontal or slightly anteriorly sloped seat will promote heel strike and anterior pelvic tilt with extension of the spine. Sacral support must also be considered to prevent the pelvis from rotating posteriorly. How much support and at what position will be dictated by findings from the mat assessment. For example, the mat assessment can determine if the client has a flexible or fixed lumbosacral junction. This determination and other modifications resulting from the evaluation collectively result in greater propulsion efficiency and improved trunk posture.

Seating adaptation for effective and efficient wheelchair propulsion is a unique and challenging practice area for the physical and occupational therapists and assistants working with older adults. Simmons et al. 1 report that in 96 observations periods involving 65 nursing home residents that were non-ambulatory and wheelchair-bound, self-propulsion occurred only 4% of the time. This low level of self-mobility was attributed to ill-fitting and dysfunctional wheelchairs and difficulty disengaging wheel locks. Wheelchair mobility is an area that physical and occupational therapists and assistants can impact. The next time a client is referred to you because she is sliding out of the chair or for mobility purposes, use your knowledge of the muscles acting on the pelvis and lower extremities to guide your evaluation and equipment prescription. There is more to this process than just floor to seat height.

References
1. Simmons et al. (1995). Wheelchairs as mobility restraints: Predictors of wheelchair activity in non-ambulatory nursing home patients, Journal of the American Geriatrics Society, 43:384-388.


Mike's Message 8.12.21

By: Mike Billings
Date: August 12, 2021


BIOMECHANICAL CONSIDERATIONS FOR WHEELCHAIR FOOT PROPULSION

By Mike Billings, PT, DHSc, MS, CEEAA

Last month I had an opportunity to tour the memory care unit of a retirement community that Infinity will begin serving soon. In me, the physical therapist immediately noticed many residents with poor wheelchair positioning and other conditions needing rehabilitation interventions. I do not consider myself a wheelchair seating expert. Still, it is one of my favorite practice areas because proper positioning can positively impact the quality of life of the older adults we serve.

As physical and occupational therapists, we are often called upon to prescribe wheelchair seating systems for our older adult clients. Sometimes, the objective is to improve positioning, prevent skin breakdown, or find an alternative to restraint use in the wheelchair. Frequently, though, it involves promoting mobility, which usually includes components of all the above.

One of the most common reasons for referral to therapy for a seating evaluation is the client’s problem of continually sliding out of the wheelchair. Though less common now, some wheelchair restraint devices may have already been tried without success. Yet, the client continues to demonstrate poor positioning, requiring frequent repositioning by the caregiver. Aside from restraint use being unacceptable in today’s nursing home environment, this type of solution fails because it is not specific to the client’s individual needs.

The only way to determine the valid reason for the apparent positioning problems is through a detailed assessment, including gathering background information from the medical chart and patient, family, and caregiver interviews, current equipment setup, environment, and a thorough evaluation on a therapy mat.

There are many factors to consider when determining a proper wheelchair setup. The most obvious is the height of the seat to achieve adequate heel strike. Most nursing homes are equipped with a fleet of standard sling-seat and sling-back wheelchairs that are eighteen inches wide, forcing the clinician to adapt it to the correct height. In addition, the client’s heel to knee length must equal the overall seat to floor height. A lower seat to floor height can be accomplished using smaller diameter rear wheels, castors, or a drop seat.

Seat height is only part of the solution. To complete the process, we have to refer to our evaluation findings and apply our knowledge of anatomy and kinesiology. The primary focus should be on the pelvis. Recall that when it tilts anteriorly, the lumbar spine goes into extension. When the pelvis tilts posteriorly, the lumbar spine goes into flexion. To keep the pelvis in the most functional position possible, we must also realize that it anchors many major muscles. For example, the extensors of the spine, iliopsoas, some hip adductors, and the rectus femoris muscles all act upon the pelvis to tilt it anteriorly. Conversely, the abdominal, hamstring, and gluteus maximus muscles act upon the pelvis to tilt it posteriorly.

To make the wheelchair move, the client must work against rolling resistance and create friction against the ground with the heel. This effort requires a tremendous amount of energy because standard wheelchairs can weigh as much as 50 pounds. Not only is it essential to get the feet on the ground, but also to observe their position. You can test this on yourself by placing your feet forward on the floor while sitting and pressing your heels straight down. The upper body tends to push back into the chair, while the hamstrings pull the pelvis into a posterior pelvic tilt and may even cause the pelvis to slide anteriorly in the chair.

Alternatively, when sitting in a 90-90-90 position and pressing the heels straight down, the upper body tends to move straight up. Now put your feet under the seat and push your toes straight down. The upper body tends to lean forward. This activity demonstrates how muscles connected to the pelvis act differently depending on where the foot puts pressure on the floor. If the resistance is great, these compensations become more pronounced.

These compensatory movements may also become noticeable when the wheelchair is inadequate. For example, suppose the seat is too high. In that case, the client tends to slide anteriorly in the chair and propels with the plantar flexors and hamstrings, which promotes even greater posterior pelvic tilt and anterior sliding. The client may also lean forward to compensate, thereby becoming at risk for falling out of the chair. Conversely, suppose the seat is too low. In that case, the distal thighs tend to rise off the seating surface, placing greater pressure on the ischial tuberosities. Or the client may slide anteriorly in the chair with the upper body pushing back into the chair.

Unfortunately, a common solution in nursing homes to sliding forward out of the wheelchair is to place a wedge cushion in the chair. The client then must fight harder to overcome the even greater floor to seat height or cannot accommodate the greater hip flexion that the wedge cushion causes and slides further anteriorly in the chair.

So what adjustments should be made? Since forward propulsion promotes flexion of the spine, posterior pelvic tilt, and anterior migration of the pelvis towards the front of the chair, a contoured cushion can be used to stabilize the pelvis and keep it centered in the back of the chair. In addition, a solid horizontal or slightly anteriorly sloped seat will promote heel strike and anterior pelvic tilt with extension of the spine. Sacral support must also be considered to prevent the pelvis from rotating posteriorly. How much support and at what position will be dictated by findings from the mat assessment. For example, the mat assessment can determine if the client has a flexible or fixed lumbosacral junction. This determination and other modifications resulting from the evaluation collectively result in greater propulsion efficiency and improved trunk posture.

Seating adaptation for effective and efficient wheelchair propulsion is a unique and challenging practice area for the physical and occupational therapists and assistants working with older adults. Simmons et al. 1 report that in 96 observations periods involving 65 nursing home residents that were non-ambulatory and wheelchair-bound, self-propulsion occurred only 4% of the time. This low level of self-mobility was attributed to ill-fitting and dysfunctional wheelchairs and difficulty disengaging wheel locks. Wheelchair mobility is an area that physical and occupational therapists and assistants can impact. The next time a client is referred to you because she is sliding out of the chair or for mobility purposes, use your knowledge of the muscles acting on the pelvis and lower extremities to guide your evaluation and equipment prescription. There is more to this process than just floor to seat height.

References
1. Simmons et al. (1995). Wheelchairs as mobility restraints: Predictors of wheelchair activity in non-ambulatory nursing home patients, Journal of the American Geriatrics Society, 43:384-388.

© 2019 Avamere Family of Companies
© 2019 Avamere Family of Companies
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© 2019 Avamere Family of Companies