In previous Clinical Corner articles, I have written about generic off-the-shelf wheelchair cushion design and materials, cushion covers, and wear in wheelchair cushions. I have also written about customizing off-the-shelf seating to address skin protection, positioning needs or personal choice. All of these articles can be accessed by either using the search toolbar in the upper right corner or by clicking on the appropriate tag in the lower right corner of the blog. This month, let’s continue to look at seating with a focus on custom seating.
Custom seating is the fabrication of a cushion and/or back to meet the unique presentation of an individual that cannot be met through customizing off-the-shelf seating alone. Custom seating is chosen to help meet clinical goals, such as accommodating moderate to severe postural deformities, minimizing the progression of current postural deformities, inhibiting abnormal reflexes, controlling muscle tone, promoting function through proximal stability, facilitating skin protection through even pressure distribution, and comfort or sitting tolerance.
There are two different types of custom seating – custom configured and custom molded. Selecting one type of system over another will depend upon a number of different factors, including the need for growth in the system, the transfer technique used, and the need for heat and moisture dissipation.
Custom configured seating can be used to form seat cushions and back supports, through the use of layering of materials. Seats that are created through foam layering can be customized to any required anatomical shape, such as a wedge seat, an anti-thrust seat, a contour seat, and a split seat. Such cushions begin with a base made of wood, upon which different layers are added to form the unique anatomical shape required, such as creating a contour for the pelvis and troughs for the legs. Materials, such as foam layers, are chosen based on their properties and the desired outcome for the seating. Selecting foam types in various thicknesses helps to achieve pressure relief, immersion and/or stability. Combining the foams, or other materials, such as gel, in different combinations of layers, and forming the required shape for an individual, helps to achieve the desired goals of seating. Back supports may also be custom-built, again beginning with a wood base and building different layers to form the unique shape required to meet seating goals. Covers are sewn to match the unique shape of the seating system.
There are many benefits to custom configured seating. It can be built to allow for growth or expected changes in an individual. In addition, depending upon the selection of materials, such seating can also facilitate heat and moisture dissipation. Because the contours may not be as great in custom configured seating as they are in custom molded seating, configured seating may be easier for transfers in some cases. There are also benefits to custom molded seating. Custom molded seating conforms to the unique postural presentation of an individual. By providing intimate contact over a large surface area, both average and peak pressure over bony prominences can be reduced.
There are many types of custom molded seating systems, some of which are created using a direct mold of the individual and others which are created using an indirect mold. Foam-in-place is an example of a direct mold. In this case, liquid foam is used to mold to the shape of an individual’s body. The liquid foam is poured into a plastic bag and the chemical reaction that occurs when the liquid foam is prepared causes the foam to expand to create the contours required. In an indirect mold, a person’s shape is captured in a medium, which is used to then manufacture a custom molded cushion and/or back. When creating custom molded seating systems, it is often beneficial to work as a team, with a therapist positioning the person into the optimal position for that person and another person working with the materials.
With either custom configured or custom molded seating, it is important to consider the hardware that will attach the seating to the frame of the wheelchair. For example, if a transit-approved option is required, a universal, knob-style transit hardware should be selected. (Look for a future article of Clinical Corner for more on standards for wheelchairs and seating devices for use in motor vehicles.)