Postural Support Devices

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Introduction

Wheelchair users are people who already have a wheelchair or who can benefit from using a wheelchair because their ability to walk is limited. Wheelchair users include:

• children, adults and the elderly; girls, boys, women and men;
• people with different health conditions, lifestyles, life roles and backgrounds;
• people living and working in different environments including rural, semi-urban and urban.

The needs of each wheelchair user will vary. However, all wheelchair users need an appropriate wheelchair.

Every well-fitting wheelchair provides the user some postural support. The backrest, cushion, footrests and armrests all provide postural support when adjusted to suit the wheelchair user’s size. However many children and adults need additional postural support in their wheelchair.

Additional postural support can be provided by a Postural Support Device (PSD) – a physical device that provides additional postural support. Postural Support Device is an essential element of intermediate level wheelchair service. This includes any addition or modification to a wheelchair for providing additional postural support.

What is posture and why is important to sit upright?

Most wheelchair users spend many hours sitting. This means that their wheelchair is not just a mobility aid. It also helps to support them in sitting upright comfortably.

Posture is the way a person’s body parts are arranged. Wherever possible, a well-fitting wheelchair should support wheelchair users in sitting in an upright posture. Sitting upright helps wheelchair users in many ways. Sitting upright is good for:

• health: an upright posture helps with digestion of food and breathing;

• stability: an upright posture is more stable;

• weight distribution: when sitting upright body weight is evenly distributed – this helps to reduce the risk of pressure sores;

• comfort: when body weight is distributed evenly, it is more comfortable for the user;

• preventing problems with posture: sitting upright will help to reduce the chance of developing deformities of the spine in the future;

• self-esteem and confidence: sitting upright can help wheelchair users feel better about themselves.

Even though sitting upright has many benefits, without postural support it can be hard to stay in this posture all day. This is why people without a disability use different postures throughout the day. For a wheelchair user who sits in a wheelchair all day, the wheelchair needs to provide enough support to help the user to sit upright comfortably.

When is additional postural support needed?

People need additional postural support for different reasons. Usually it is clear when a wheelchair is not giving enough support to help the wheelchair user sit upright as outlined below. Often wheelchair users, or the family member/caregiver will have good suggestions themselves about what further support they may need.

Reasons for needing additional support include:

• cannot sit upright;
• uncontrolled movements or spasms;
• joint stiffness;
• tightness;
• weakness;
• fatigue;
• pain or discomfort;
• difficulty balancing.

How does additional postural support help?

There are four very important ways that additional postural support can benefit wheelchair users;

Improves balance, posture and stability

Improving balance, posture and stability can help a wheelchair user to carry out activities that are not possible or very difficult for them without additional postural support.

Improves comfort

Additional postural support can make a wheelchair much more comfortable and can increase the time wheelchair users are able to sit in their wheelchair before becoming tired.

Helps to prevent the development of pressure sores

A pressure sore can develop very quickly. Good postural support helps to prevent pressure sores by making sure that one part of the body is not overloaded. One benefit of sitting upright is that weight is evenly distributed. This helps to reduce the risk of a pressure sore.

When a wheelchair user does not sit upright, their weight is unevenly distributed. One part of their body will take more weight than other parts. If that additional weight is on skin, which lies over a bony area, there is a high risk of pressure sores.

Examples of bony areas include the seat bones (ischial tuberosity), ribs, hips (trochanters), spine (vertebra) or tail bone (coccyx).

When a wheelchair user is not well supported, he/ she tends to slide on the seat. This causes shear, which leads to pressure sores. Sitting well supported prevents sliding and shearing.

Helps to slow down or prevent the development of problems with posture in the future

Good postural support can prevent problems with posture developing. If a problem with posture has already started, good postural support can slow down or prevent this from getting worse. Good postural support in lying, sitting and standing, started as early as possible is important.

Eating and drinking safely

Some wheelchair users who have difficulty sitting upright also have problems with swallowing safely. For these people, eating and drinking can be uncomfortable, sometimes frightening, and often dangerous. When people have difficulty swallowing safely, small pieces of food and drink may go into the lungs. This can cause a chest infection, making them very ill or even choking leading to death.

Additional postural support in a wheelchair ensures that the wheelchair user can sit upright when eating and drinking.

Improving postural support is just one part of the solution for anyone who has problems with swallowing. If at all possible, children or adults with problems swallowing should be referred to someone who has experience in managing this. This could be a paediatrician, speech language therapist, or any allied health or community health worker who has knowledge and training in helping people manage problems with swallowing.

What do wheelchair users want?

Wheelchair users want to be comfortable and able to get on with their lives. It is important that additional support in the wheelchair does not make day-to-day activities harder.

For example, additional postural support should not interfere with transferring in and out of the wheelchair, propelling the wheelchair, accessing desk or workspace and transport.

A wheelchair and additional postural support should always:

• be practical and easy to use;
• be comfortable and not cause additional discomfort;
• help wheelchair users to do things and not make them more difficult;
• look good and not be too ‘obvious’.

Sometimes wheelchair users find it hard to get used to a wheelchair with additional postural support.

There are different reasons for this including:

• the wheelchair user may be used to sitting in a certain way. The additional postural support, which changes their habitual posture, feels uncomfortable or restrictive;
• the wheelchair user may not understand why the additional support has been prescribed;
• the wheelchair user may feel the additional postural support does not look good and makes his/her disability more obvious. For these reasons, it is very important that wheelchair service personnel work closely with the wheelchair user and their family/caregiver throughout the assessment, prescription, fitting, user training and follow up steps. Always discuss solutions with the wheelchair user and always respect their input and final decisions. The best way to make sure additional postural support will be used by wheelchair user is to:

• fully involve the wheelchair user and their family member/caregiver in their assessment, prescription, fitting, user training and follow up;
• help the wheelchair user and their family member/caregiver to understand why and how additional postural support will help them;
• always let the wheelchair user make the final decision.

Classification of Postural Support Device cushions

The best-known is the classification by user need. Although not as well known, the other methods of classification provide useful information on construction materials, the different functions of the cushions and their ability to prevent pressure sores.

Classification by user need (Hobson)

This classification was proposed by David A. Hobson, at the University of Pittsburgh Rehabilitation Engineering Center in the United States [Smith and Leslie, 1990]. It divides PSDs into three categories, which are defined mainly on the basis of the needs of the different user populations, namely, those designed to:

1. Provide postural support and compensate for deformations (individuals with cerebral motor impairment).
2. Balance pressure and maintain posture (individuals with spinal cord injury).
3. Improve comfort and posture (individuals with multiple handicaps and the elderly).

Classification by construction material

Most often, seat and back cushions are classified according to their shape and constituent material. From the standpoint of materials, cushions can be divided into three categories:

1. Fluid-filled cushions (air, water, elastomer gels and viscous liquids);
2. Foam cushions; and
3. Hybrid models,

These cushions can be static or dynamic. Fluid-filled and foam cushions are static devices designed to even out or distribute pressure on the pelvic contact surface. Dynamic cushion models are based on the principle that high local pressure can be tolerated as long as the duration of contact does not exceed certain preestablished limits. A few applications of this principal have been attempted. For example, there is, in essence, a mechanical model and a model consisting of bellows-type air cells.

Classification by function (Staarink)

Staarink [1995] developed a function-based classification of seat and back cushion parameters. These functions concern:

1. The seated position (quality of pressure distribution, suppleness of the surface, etc.).
2. Moisture and heat (moisture and heat control properties).
3. The action of sitting in and getting out of the wheelchair (indentation in the sacral, frontal and lateral regions, friction, puckering, etc.).
4. Transport (weight, size, portability, etc.).
5. Maintenance (textile cover washability, nontextile cover cleanability, odor resistance, etc.).
6. Durability (of the cover and cushion, wear resistance).
7. Reliability (fill-ratio sensitivity, sensitivity to positioning, etc.).
8. Safety and fire resistance.

Postural cushions

A pressure relief cushion will help to reduce pressure. Anyone at risk of developing a pressure sore should be given a pressure relief cushion.

Different types of cushions

Cushions can be described in different ways, including:

• the material they are made from (for example foam, coir);

• the material they are filled with (for example air, fluid or gel);

• their main function (for example pressure relief, comfort, posture support);

• their shape (for example flat or contoured);

• how they are made (for example foam cushions may be “moulded” from one piece of foam or “layered” – made from a number of layers of foam).

The most commonly available cushion is a foam cushion. Foam cushions are also usually the least expensive. They are easy to make where foam is available and easy to modify to suit individual wheelchair users.

Pressure relief cushions

There are different types of pressure relief cushions including:

• Foam contoured pressure relief cushions;
• air/fluid/gel filled cushions.

Foam pressure relief cushions

The key features of a foam pressure relief cushion are the following:

1. Firm stable base: The base of a pressure relief cushion should be firm. This will make sure the cushion provides good support for the user and does not move when the user moves.
2. Top layer: Over the base layer there should be a “comfort layer”. This is a layer (or more than one layer) of softer foam. The top layer should be soft enough to allow the seat bones to sink into it, but should not be so soft that the seat bones can sink all the way to the bottom and rest on the solid base or seat of the wheelchair.

Pressure relief cushions help to reduce pressure by:

• Distributing a wheelchair user’s weight as evenly as possible across the seat surface;
• Reducing pressure under high-pressure risk areas (seat bones, hip bones, coccyx/tail bone);
• Reducing shear by assisting the wheelchair user to sit upright.

Which cushion to use?

There are advantages and disadvantages of both foam contoured cushions and air/fluid/gel cushions.

	Advantages	Disadvantages
Foam contoured cushion	Can be made locally (where there is high-quality foam). Can be modified locally to accommodate different needs. Not subject to”sudden collapse” (a puncture in the air/fluid/gel cushions can cause the release of the materials from the cushion and stop the cushion from relieving pressure, causing “sudden collapse” of the cushion). The top layer of a layered foam cushion can be replaced easily and at a low cost (rather than replacing the whole cushion).	Foam compresses (becomes flatter and firmer) over time. For this reason, foam cushions should be checked regularly and replaced every 1–2 years. Can take a while to dry out (a problem for people who are incontinent). Foam insulates and can cause an increase in tissue temperature.
Air/fluid/gel cushions	Pressure is distributed evenly over the seat surface. The gel pad automatically adapts to the body when the wheelchair user moves or changes position.	Air/fluid/gel cushions are often more expensive and less readily available than foam cushions. Some wheelchair users find air/ fluid/gel filled cushions make them feel unstable. Subject to “sudden collapse”. In any context where a wheelchair user is not able to get a replacement cushion quickly, this can be a problem.

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