Last month’s Clinical Corner article focused on Selecting a Cushion Based on Seating Goals. The article highlighted the importance of conducting a thorough assessment and establishing goals for seating and mobility. Common goals of seating and mobility were outlined. These include: pressure management, positioning, function/stability, heat and moisture dissipation, impact and vibration dampening, comfort, or a combination of the goals. As I mentioned last month, both the cushion and the back support work together to achieve desired results. This month, let’s continue the discussion and focus on generic product parameters in back supports to help achieve client seating goals.
Before we begin our discussion of how back supports help to achieve client seating goals, let’s have a quick review of considerations related to back supports, sizing, and modifications. These topics have been addressed by past Clinical Corner articles. Please refer to:
- Seating Considerations - The Back Rest. This 2011 Clinical Corner article outlines the assessment information that translates to generic product parameters, including presenting posture, trunk stability and body dimensions.
- Understanding Seating Sizing. A section in this recent Clinical Corner article describes how to use anatomical measurements to order the correct size of back support to ensure optimal fit for the client and for the wheelchair.
- Modifying Off-the-Shelf Seating. Some possibilities for modifying back supports, such as adding external laterals, selecting alternate covers, and painting the back shell for aesthetics, are reviewed in this 2013 Clinical Corner article.
Now, let’s look at common goals of seating to see how the back support can help to achieve these goals.
Pressure management through the trunk can be achieved in a number of different ways. By adding shape to a back support, the surface contact area between the client’s trunk and the back support can be maximized, which helps to reduce pressure at contact areas. Although off-the-shelf back supports may have lateral contours, the posterior surface of a back support is flat. Whether an individual has a normal “S” curve of the spine, a lumbar lordosis, or a kyphosis, not all areas of the trunk will make contact with the planar surface unless shaping components are added to the back support. Often, they can attach with velcro between the foam of the back support and the aluminum or carbon fibre shell to build shape and maximize surface contact area.
Skin also can be protected with the addition of a fluid pad over the spinal area in a back support. Since fluid adds weight to a foam back support, it is added only where needed – along the spinal processes – to protect the bony prominences that can be at risk for skin breakdown for some individuals. For those individuals where shearing forces are a concern, such as individuals using manual dynamic recline in a wheelchair, the addition of a fluid pad reduces shear forces along the bony prominences.
In addition to adding shape to a back shell, adjusting the angle of the back support through the mounting hardware also helps to take load through the trunk, which helps to manage pressure. There are various degrees of angle adjustability available through hardware choice. By adjusting the angle of the back support, gravity can be used to assist with positioning and with taking load through the trunk. In addition, when the trunk takes load, the peak and the mean pressure through the cushion can be reduced.
Just as shape and angle adjustability affects pressure management, it also affects positioning. Desired positioning can be achieved through the use of positioning components that add shape to the shell and with more open seat to back angles through mounting hardware. For example, for a client seated with a kyphosis that requires accommodation, positioning pieces can be added at the top and bottom sections of the back support that help to position the trunk, and mounting hardware can create a more open seat-to-back angle, to decrease the potential for further worsening of the posture as gravity acts down on the individual.
Back supports are available in many different depths or contours. Some back shells are shallow, offering just over 2 inches of contour; while others are deep, offering 6 inches of contour. The contours of the shells provide support where needed to aid in positioning; for example, at the hips or at the mid-thoracic level.
In combination with the cushion, the back support offers postural stability, which can enhance function; however, if the back support and mounting hardware is not optimal for an individual, the back support can interfere with function. For example, a back support that is too tall or too deep with respect to the lateral contour of the shell may interfere with propulsion for an individual. A shell that is too shallow for a client who presents on mat assessment as requiring more lateral support also may interfere with function as the client is not provided with sufficient stability in the seating system to promote function. It is a fine balance between neither over-prescribing nor under-prescribing a back support for an individual.
When we think of function, we should also think of transportation. If the firm back support is to be removed from the wheelchair to enable folding of the chair for transit purposes, we should think about how easy it is to remove/replace the back support for the client or caregiver. If the client is to remain seated in the wheelchair for occupied transit, we should be thinking of back supports that have been crash-tested to ensure the back support can withstand the forces in a collision or near-collision event to prevent harm from occurring to the individual who remains seated in their wheelchair while in transit. See WC20 and Secondary Postural Supports When Traveling in Motor Vehicles for more information on the occupied transit standard related to seating.
Heat and Moisture Dissipation
Heat and Moisture Dissipation in Seating, a 2017 Clinical Corner article, provides some insight into new innovations in back supports that address heat and moisture dissipation. In addition, the article reviews the effect of material and cover options and how they address heat and moisture.
Impact and Vibration Dampening
For some clients, the effects of impact and vibration must be lessened in order to permit comfort and function. For these clients, we must consider effects of back support material on impact and vibration dampening. Air and foam are known to offer low impact transmission of vibration, while gel and fluid offer higher impact transmission. Many back supports are manufactured with foam, which will decrease the effect of impacts or vibrations.
Comfort is subjective. What one person finds comfortable, another person may not find comfortable. Some considerations that may indicate comfort in a back support include the type and thickness of foam used in the back support, the foam wrapping around any hard edges, the material of the cover (e.g., stretch material to allow for immersion into the foam of the back support), and the angle adjustability available in the hardware.
This month’s Clinical Corner article continued to look at the six common goals of seating – pressure management, positioning, function/stability, heat and moisture dissipation, vibration dampening, and comfort. The focus this month has been on back supports. Generic product parameters for back supports, including shell contour and height, angle adjustability, and back support and hardware design, were identified to show how they work to help to achieve the various goals.