Education in Motion / Clinical Corner / May 2022 / More About Working with Fluid Wheelchair Cushions - The Base

More About Working with Fluid Wheelchair Cushions - The Base

Fluid cushions are versatile to meet the pressure management and positioning needs of individuals. We have discussed how to modify the fluid volume to address these needs. Now let's review additional modifications that are available to meet other positioning and functional needs.

Did you know that fluid cushions can be modified to provide scrotal relief? Both the base and the fluid pad can be modified to address this concern for an individual. The base of the cushion can be modified with a scoop out at the front and centre of the pelvic loading area to accommodate organ tissue, reduce discomfort, and increase sitting tolerance. (See bottom left photo.) The scrotal area of the fluid pad can be heat sealed to control fluid migration in order to reduce pressure in areas that are at risk for skin breakdown, pain, or discomfort. (See bottom right photo.)

Thigh and pelvic supports can be added to fluid cushions to help achieve orientation of the pelvis and alignment of the thighs in the seated position. Lateral pelvic supports at the rear of the cushion may help improve sitting posture for an individual with narrow hips as the supports help to orient the pelvis to the contoured well of the cushion. A medial thigh support adds a positioning piece to the front middle of the cushion to provide abduction to position the thighs. Lateral thigh supports are added to the lateral edges of the front of the cushion base to draw the thighs toward the median for adduction. The photo below left represents thigh and pelvic supports attached to a closed cell foam base as the pieces can be attached directly to this type of foam. The photo below right shows positioning pieces added to the pockets of an inner cover of an open-cell foam cushion as the positioning pieces cannot be attached directly to open-cell foam. An outer cover is used with both types of foam bases.

For an individual with different femoral lengths, a leg length cut decreases the length of the foam base and fluid pad (if applicable) on the left or the right side (see below) and provides a cushion cover to match the modification to accommodate the leg length discrepancy.

A contracture cut, in which a 45° angle is undercut at the front of the foam base (see below), has many clinical applications. This modification permits clearance for calves when tight hamstrings, close thigh-to-lower-leg angles, or large calves present. In addition, a contracture cut accommodates foot propulsion by providing clearance for the lower leg while also providing femoral support.

Another modification that is important to know about is how to create a slope in the cushion, whether it is a posterior slope or an anterior slope. A posterior slope closes the seat to back angle to provide postural stability for individuals when it is clinically appropriate (for example, a posterior slope is not to be used as a "quick fix" to prevent sliding as this does not work). A posterior slope can be achieved through one of two ways. Either through an angle cut (as shown in the picture on the bottom left) or through the addition of a wedge glued to the base of the cushion. For the angle cut posterior slope, material is removed from the base of the cushion, such that the front of the cushion is higher than the rear of the cushion by the specified dimension. For the wedge posterior slope, the added wedge raises the height of the front of the cushion by a specified dimension, which increases the finished seat to floor height at the front of the cushion.

The opposite occurs for the anterior slope, which is used to open the seat-to-back angle to accommodate hip flexion limitations and assist with foot propelling and transfers. Again, either an angle cut or a wedge glued to the base may be used to create an anterior slope, such that the back of the cushion will be higher than the front of the cushion by the specified dimension. Either foam is removed at an angle from underneath the front of the cushion base, as in the angle cut anterior slope (bottom left), or a wedge is added to the base of the cushion, as in the wedge glue anterior slope (bottom right).


Many modifications are possible on wheelchair cushions to help achieve seating and positioning goals.

Please send your comments, questions, and suggestions for Clinical Corner topics to Sheilagh Sherman, OT Reg. (Ont.) at Thank you!

Note: The content of this article is not meant to be prescriptive; rather, it is meant as a general resource for clinicians to then use clinical reasoning skills to determine optimal solutions for individual clients. Sheilagh is unable to answer questions from members of the general public. Members of the general public are directed to their own therapists or other health care professionals to ask questions regarding needs.

This article is © Sunrise Medical, Inc., 2022 and cannot be copied, distributed, or otherwise reproduced in whole or in part without the express written permission of Sunrise Medical Canada.

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