The intricacies involved with manual wheelchair measurements and configurations to improve mobility.
By Kirsten Davin OTD, OTR/L, ATP, SMS
It is difficult to overstate how important it is to configure a wheelchair correctly to meet the client’s needs. A manual wheelchair that is properly fitted to the user can often lead to greater independence, better performance in daily living activities, better posture support, and reduced risk of skin integrity or pressure injury. Accurate measurements of the user’s anatomical structure and wheelchair may also improve their ability to self-propel. All of these benefits have a positive impact on the quality of life of wheelchair users.
Anatomical measurements can be obtained by measuring the client’s anatomy, whereas wheelchair measurements can be acquired by measuring the chair, sometimes in comparison with the floor or the client’s position.
Fundamental Measures
Most people are familiar with the standard anatomical measures that are used to fit a client with good trunk control to a manual wheelchair. These measurements can include, but not be limited to:
Seat Width – To determine the correct width of the wheelchair seat, measure the distance between the widest point of the user’s buttocks or hips. The wheelchair seat needs to be wide enough to not put pressure on the buttocks, lower extremities or hips of the user. It is recommended that you add 1 inch to this measurement in order to ensure lateral clearance.
Seat Depth – Used to determine the correct length (depth) for the seat, this measurement is taken from the user’s posterior buttock along the lateral leg to the back of their knee, also known as the popliteal space. To avoid pressure from the front edge or cushion of the seat against the popliteal area, typically a space of about 2 inches is maintained. However, this can vary depending on the user’s preferences and clinical recommendations.
Seat Height – This measurement is taken from the heel of the wheelchair user to the popliteal fossea. When used to select equipment, it should allow the user’s heels to reach the ground with a functional strike when seated, in the event that they will be self propelling. Seat height may need to be raised for clients who will use footrests. This clearance is typically 2 inches above the floor.
Armrest Height – This measurement is used to determine the height of the armrest in relation to the user’s anatomy. The user must be seated upright with neutral shoulders and the distance between the top of their wheelchair seat and the bottom of their elbow must be measured. In general, 1 inch of additional support is provided to the upper extremity.
K0005 Ultralightweight
The ultralightweight wheelchair, also called a K0005 Ultralightweight Manual Wheelchair, allows for the most adjustment and therefore requires the most detailed and intricate series of measurements.
A K0005 ultralightweight wheelchair allows the clinician or assistive technologies professional (ATP) to incorporate unique specifications, including seating and frame adjustment and proper axle placement, to create a wheelchair which offers a precise fitting to the user. This results in enhanced performance, maneuverability and stability.
Clinicians can test the K0005 wheelchair with the correct axle position and precise measurement. This will allow them to demonstrate the product in the most realistic way. It could also reduce the number patient transfers and improve the time management during the evaluation.
The most important thing is to ensure that you have the correct measurements taken and implemented when preparing for a K0005 wheelchair. This will help you get funding for this equipment and complete the final configuration of the wheelchair and seating at the time of delivery.
Important Measures for Self-Propulsion
In addition to the standard measurements previously noted, additional measurements and configurations specific to a K0005 wheelchair may enhance and promote effective self-propulsion. Such measurements include but are not limited to:
Rear Seat-to-Floor Height – Measured at the rear of the wheelchair directly in front of the back frame post, this measurement, in conjunction with the front seat-to-floor-height measurement, comprises the degree of seat slope. The rear seat-to-floor-height measurement is taken from the top of the wheelchair seat to the floor.
The rear seat-to-floor height aids in determining the location of the rear axle’s vertical placement, by ensuring the client has adequate access to the wheelchair’s hand rims in order to achieve optimal self-propulsion. When assessing a wheelchair user’s fit within the chair, ask the user to sit in the chair. The tip of the user’s middle finger should align with the wheel’s axle, indicating correct positioning and resulting in efficient self-propulsion.
Front Seat-to-Floor Height – Measured at the front frame of the wheelchair, where the anterior portion of the seat conjoins with the frame, the front seat-to-floor height is measured from this location to the floor.
A front seat-to-floor height that correlates well with the client’s anatomical measurements will provide adequate support of the femur and lower extremities to produce favorable stability and pressure distribution. It may also aid in reducing the risk of skin breakdown.
When determining both the front and rear seat-to-floor height, and how these measurements play into the entirety of the wheelchair fit, it is imperative to consider the height, or thickness, of any wheelchair cushion that may be in use. Some wheelchair cushions—for example, an anti-thrust or wedge cushion—are designed with greater anterior thickness, and a reduced posterior height. You’ll need to include cushion height, both anterior and posterior, in the overall calculation and fit, for if it is not accurately considered, seat slope may be affected.
Seat Slope
In an optimally configured manual K0005 wheelchair, the front and rear seat-to floor-height measurements are not always equal. Seat slope (also known as “seat dump”) is the difference between front and rear seat-to floor height. This is a very important adjustment, as the correct seat slope is essential for overall postural stability.
The benefits of incorporating an appropriate seat slope include increased postural stability and pelvic control for those with reduced trunk control. Accurate alignment between the upper extremity and the drive axle can also be beneficial. This, combined with improved postural control, can lead to a significant improvement in wheelchair self-propulsion and maneuverability.
The benefits of a steeper seat slope are obvious, but it can also cause complications. If the addition of significant seat slope causes the wheelchair to promote a greater degree hip flexion than what the user can tolerate or perform, or if it narrows the angle between the seat and back to the point where the user is unable to comfortably or effectively fit in the chair, then the user may pull out of the seating system or settle into an inappropriate pelvic tilt. It is helpful to visualize the overall fit by using a demonstration wheelchair that has been set up similarly to the final chair.
If a conventional slope seat cannot be implemented for various reasons, including those listed here, an ergonomic (ergo-) seat could offer a viable alternative. An ergo-seat creates the desired shape via a bend on the wheelchair frame. This allows the frame to be adapted to the client, rather than trying to accommodate via seat angle.
Rear Axle and Self-Propulsion
When evaluating the client for a new manual chair, the anatomical measurements and wheelchair measurements listed here, along with the comprehensive seating assessment, will help to position the user’s upper body and extremities at the optimal location for self-propulsion. When the rear axle is positioned directly beneath the user’s mass center, they experience greater ease of self-propulsion. They also experience reduced friction forces and less repetition using their upper extremities to propel the wheelchair. This will reduce the risk of upper extremity syndrome.
The horizontal position of the rear wheel has a major impact on the overall stability, weight distribution and propulsion efficiency. As noted above, the fingertip placement technique can be used to confirm the correct horizontal placement of the back axle.
When the rear wheel is placed under the mass center of the client, 80% or more of their weight should be seated on the rear wheel. The remaining 20% of their weight can be distributed between the leg rests and foot plates, as well as the front casters. If the weight is too evenly distributed on the front casters and other factors, it will require more force to self-propel. This can lead to increased stress to the upper extremities, as well as an increased risk of repetitive injury.
If the horizontal position of the rear wheel is too far forward, it will not only result in less self-propulsion efficiency, but also in increased rolling resistance and a tendency for wheelchairs to tip backward. It will also be more difficult to maneuver the wheelchair, which can include performing wheelies in order to maneuver obstacles.
The creation of a comfortable seating system is influenced by the measurements of the wheelchair and the user, as well as the visual assessment of their fit in the wheelchair. This will not only improve the self-propulsion of your client but also reduce the risk of injury from overuse. This can make all the difference to your client’s health.
Original Blog: https://rehabpub.com/mobility/manual-wheelchairs-mobility-seating/wheelchair-positioning-for-ideal-propulsion/
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