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Cushion Selection Criteria

A good cushion should:

  • Prevent tissue deformation
  • Conform to the user’s shape
  • Not bottom out
  • Support the sides
  • Be patient acceptable

Sumed Cushion Wallchart

Product Characteristics

The following are some of the important factors that should be considered in matching users’ needs to cushion product characteristics. Assessment of an individual should as far as possible take in to account the different functions of the cushion types.

Mechanical Stress Distribution

  • Shear
  • Pressure Redistribution
  • Friction
  • Displacement
  • Contact Area
  • Suspension/Shock Absorption
  • Comfort


  • Slippage
  • Restoring Force
  • Crash

Safety/Infection Control

  • CE Mark
  • Fire Retardancy
  • Mechanical Security
  • Urine Resistance
  • Cleaning
  • Waterproofing


  • Skin Compatibility
  • Allergic Reaction


Physical Description

  • Weight
  • Dimensions
  • Power Requirements
  • Noise

Insulation Properties

  • Vapour Transfer

Durability Properties

  • The performance of the subgroups over time

The characteristics listed above are parameters of function, that will be addressed, to a larger or smaller degree, dependent on the product type. For instance, a foam/liquid cushion may not exhibit the same degree of pressure distribution as a foam cushion. However, it will exhibit further functions, in other areas within the Mechanical Stress Re-Distribution sector eg displacement, shock absorption or stability.


Following are some of the criteria that should be considered during the assessment process:


It is very important to maintain as near as possible an angle of 90° at the hip and knees. This position provides the largest surface area for the cushion to relieve pressure. The two 90° angles should ensure that there is a more equal loading across the cushion surface. Great care should be taken to ensure the wheelchair/chair is set up according to the users’ needs and that no undue pressure is placed on the sacral/ischial area or the front of the thighs. Posture may be enhanced using a back support.

The hammock effect caused by stretched seat canvasses can lead to:

  • Chaffing at the knees
  • Sweat and heat build up

If a solid board is used to counteract the hammock effect, ensure it cannot slide off the side bars of the wheelchair, as this leads to pelvic obliquity.

Adduction and Abduction

Should be minimised and it is important to evaluate the user’s requirements in this area. Some users may need the added function addressed by some cushion types. eg cushions with contouring of the base and component sets, to enhance this function.

Functional Ability

This refers to the ease of transfer. Depending on the user, a low cushion may be required or one with a coated cover material. Alternatively, if the wheelchair seat canvas is slack, a deeper cushion may sit low enough to enable easy transfer. Cushion height is also an important consideration when evaluating daily living conditions. eg can the user get their legs under their dining table?

Other Considerations

These may include looking at the dietary needs of an individual as well as medication. These factors can have a severe effect on skin and particularly skin tissue, which must be taken into account when evaluating the category of cushion type. For similar build and physical characteristics, if an individual is being treated for eg thickening of the blood, he or she may require a cushion with better performance characteristics.


In accordance with the requirements of the NHS (National Health Service) Framework Agreements, each of the cushions contained in this brochure is categorised according to the following classifications:

  • Comfort – no medical properties
  • Low-risk non-therapeutic – contains preventative properties in relation to pressure relief eg foam only type
  • High-risk non-therapeutic – contains preventative properties in relation to pressure relief eg foam type with added function
  • Therapeutic – this categorisation is used to try and indicate the suitability due to cushion type, rather than via the use of an existing Score Guide

For example, a user may be assessed as “High risk”, however, the physical differences between two high-risk users could lead to incorrect prescription. eg a grade 5 pressure sore would according to current convention, necessitate a “high risk” categorisation. However, an individual with intact skin, but other medical conditions, would also be categorised as “high risk”. It is therefore clear that a different cushion should be prescribed for each individual. In this case, a “Therapeutic” cushion for the former and “High Risk Non-Therapeutic” cushion for the latter.