Chairs

Seating and Positioning


Class is in session

Mary Alexander, PT
Chief of
Seating and Specialized Equipment Clinic
Children's Neuromuscular Center, N J

Instructor & Lecturer:
Physical Therapy &
Pediatric Physical Therapy
Seton Hall
  Graduate School of Medical Education

Community Service Award 2004
American Physical Therapy Association, NJ Congrats!

 

lectureOK, Mary. Now,
if everyone will be seated...

Hello class.

Sitting is important. If you have ever taken a long car or plane trip you already know that sustained sub optimal seating can render you bent, contracted, and tired. Obviously, children with disabilities should have well thought out seating which allows them to function effectively and efficiently and not be further disabling. That seating should provide support, comfort, stability, and safety.

Safety is primarily what is defined in institutional regulations and transportation law. These regulatory details certainly must be considered when choosing a seating system. However, a child is not a crash dummy. Seating should go beyond impact criteria and not interfere with social interaction.

Folks may have difficulty when a wheelchair is recommended for the first time and be sensitive to how their child might look in this special equipment. That makes it all the more important to discuss any and all of concerns before any equipment is ordered. There is one perfect solution per child and an infinity of shoulda's and coulda's. Unfortunately, the logistics of cost make the process a lobster trap.

Options span adaptive strollers, adaptive seats on mobility bases, and a variety of wheelchair frames, methods of propulsion, and controls. Parent acceptance is almost as important as proper fit for the child. If you are uncomfortable with the "look" of the wheelchair, you will be less likely to use it.

As your children get older, involve them in the process of choice. Self-esteem and social acceptance are important. Many times, there are choices in the style of the frame and color. These may not seem like much, but the aesthetics of design and color do make a difference to children and young adults.

Consider your environment before ordering adaptive equipment. Will it fit into the trunk of the car? Is there an elevator in your building? At school? Ramps? How wide are the doors in your home? Are the bathroom, bedroom and living spaces large enough to accommodate the wheelchair? If you do not use a tape measure on your own living space the odds are very high that you WILL screw up. For goodness sakes, measure the desks! Measure the obvious. Can't hurt.

Adaptive equipment is expensive. Before ordering, check with your insurance company to determine the amount of coverage allowed for durable medical equipment. Most insurance has a lifetime cap on equipment (you might get only one swing at this ball). Because of the expense and limitation of coverage allowances, pediatric equipment that has the ability to "grow" with your child must be a primary consideration when ordering.

Adaptive equipment expositions are usually held annually. Expos are wonderful for finding resources and for comparing equipment options. There are demonstrations of the latest features and equipment and many hard to describe goodies are available to try before you order. Check with your physical therapist or equipment specialist in your area for local dates.

 

Seating systems require regular maintenance. When you receive a new piece of adaptive equipment, take the time to review the recommended maintenance requirements with the therapist or rehabilitation specialist. Regular maintenance will insure more safe, efficient functioning and will likely extend the longevity of the equipment.

 General Considerations and Goals:

      1      2     3

    [  Nix     Tricks   Mix   ] \

     [ Protect   Effect   Inject ]  —pick a triad mnemonic

     [ Shield   Wield   Field  ] /

1. Nix - Prevent or at least minimize deformity or Injury:
protect against pressure sores, contractures, joint deformity; improve body functions (breathing, elimination)
 

2. Tricks - Maximize Efficient Mobility and Function:
provide stable, comfortable positioning; minimize abnormal tone or movement; reduce fatigue
 

3. Mix - Promote Positive Social Acceptance and Self-esteem:
aesthetics of design and color; maximize independent function

 

Designing the Seating System:

Children with disabilities may not have the balance and control of the trunk and extremities necessary for postural stability and functional movement. The goal is to find that position which allows the best position with the most control but the least restriction.

The pelvis is the key to control with stability.

The child's pelvis may be tilted to the back or to the side or it may be rotated or both. If the tilt or rotation is not addressed with the seating system, the trunk and head will be out of alignment and the arms and legs will not function properly.

Some of the causes for the pelvis to be tilted backward are: tight hamstrings, low trunk tone, not properly positioned in the chair, the seat is too long, or the seat belt is positioned too high (above the waist). Some of the solutions include: hamstring lengthening, decrease the seat length, reposition the child in the chair, or repositioning the seat belt.

Some of the causes for the pelvis to be tilted to the side are: scoliosis, hip subluxation or dislocation, a seat that is too narrow or not firm enough. Solutions include: increasing the width of the seat, increasing the firmness of the seat, use of pelvic guides and wedges. If the pelvis is flexible the wedge should be under the buttocks on the low side. If the pelvis is fixed, the wedge should be under the buttocks on the high side. The wedging will level the pelvis allowing the trunk to better align.

Causes for the pelvis to be rotated are: abnormal muscle tone, scoliosis, leg-length difference, or hip subluxation or dislocation. Solutions include: positioning the child in mid line, check the lap/seat belt for proper position and tension, revise the seat to accommodate the difference in leg length. If the pelvic rotation is fixed, allow the pelvis and legs to rotate and position the child's head and trunk forward.

Dealing with issues at the hip.

Children should have their knees positioned shoulder width apart (or wider) when sitting. Leg rests and foot plates must be angled to accommodate this wide knee posture. Failure to position the lower leg and feet in a wider position will produce twisting strain which may cause pain and injury to the knees and hips. BEWARE! There is a never ending tendency to automatically provide seats with side structures which direct the thighs close together. If the combined thighs (or knees) are wider than the butt, these sides, if snug, will produce adduction.

Cross your heart, not your legs.

ADDUCTION IN SEATING IS BAD.

SUSTAINED SITTING ADDUCTED RUINS HIPS.

 

 

Seat sides which are square with the back rest need careful scrutiny.

    [And note this challenge. Find a single right angle in the human body. Just one. Go ahead. Challenge your friends and your doctors to name a single truly square anything in human anatomy. After you utterly fail (and you will fail) then reconsider the odd quest for right angles in braces and chairs. Beware, right angle terminology often goes by aliases such as "neutral". Right angles are NOT neutral. Churches use right angle seating to keep parishioners awake. They annoy. Some fast food places use right angle and untilted seats to subtly keep people from lingering.]

 If hips go into extension when the child is sitting, an anterior wedge of 10 – 15 degrees can be added to the seat. This will increase the amount of sitting hip flexion. That, in turn, will decrease the tendency for the child to thrust into extension at the hips by reflex.

There are two options if the hips are adducted, internally rotated, subluxed or dislocated. A wedge shaped spacer (pommel) may be added to the seat. The pommel should be widest at the knee. Pommels can make independent transfers more difficult. A second option is to use Velcro thigh straps. These straps should be wide enough to prevent pressure sores and should be positioned just above the knee. The Velcro closure allows independence in freeing the legs for transfers.

Seat Guidelines :

We recommend contoured seats and backs. They more closely match body shapes than linear supports. They also tend to help maintain better alignment and distribute pressure more evenly. The following measurement guidelines allow for better alignment and fit of the seating system for children:

Seat width: 

    1 inch on each side at the widest part of the hips

    If the seat is too narrow, skin breakdown can occur.

    If the seat is too wide, balance and stability may be decreased. The child might have difficulty with propelling independently.

Seat depth:

     2 -3 finger space from back of knee to the edge of the chair

     If the seat is too long, circulation may be impaired. The child might not be  able to maintain good pelvic position and will have difficulty propelling the chair with the feet.

 

Leg/foot rest height:

    With the knee flexed, measure from the back of the knee to the bottom of the heel. You have to consider the type of shoes the child wears and the height of the seat cushion.

    If the distance to the foot rest is too short, sitting posture is affected and the child may have increased pressure through the buttocks.

    If that distance is too long, the child's sitting posture will be poor and there may be increased areas of pressure on the back of the thigh.

     

Seat to floor height:

     Add 2 inches to the foot rest height.

    If the seat is too high, the child may have difficulty scooting back in the chair and will have difficulty transferring.

    If the seat is too low, sit to stand transfers will be more difficult and the foot plate will drag.

     

Arm rest height:

    With the child's elbow bent, measure from the seat to the flexed elbow. Remember to add the height of the cushion to the measurement.

    If the arm rest is too low, the child may have difficulty maintaining an upright posture.

    If the arm rest is too high, the shoulders will be elevated and the pressure on the elbows may cause skin breakdown.

     

Back height:

    Measure from the bottom of the buttocks to the lowest point on the shoulder blade (scapula). For children who do not need total support, add the height of the cushion to this measurement. For children who need total support, add the height of the cushion plus 3 inches to this measurement.

 

Lateral trunk supports:

    The proper placement will promote optimal alignment of the child in the seat and will distribute pressure to prevent skin breakdown. They may be place either symmetrically or asymmetrically depending on the needs of the child.

    Meaning what?

    If kids tend to lean in one particular direction, then asymmetrically placed side supports are more effective. That is, place one side higher (on the side leaned into) and the opposite support lower. This allows narrower control without squeezing the juices out of the youngster.

    "Molded Seats" work in some places (always hot or always cold), but often fail when clothing may be thick or thin with weather changes. Consider weather realities before going the fixed molded shape route.

 

Head supports:

    These are usually necessary when transporting all children regardless of their head control. The amount of support varies with the type of head rest chosen. There are foam contoured supports of various heights and widths, which are based on the individual child's need. The Whitmeyer head support system allows for a wide combination of pads which may meet the child's need more easily. 

 

Cushions:

    Usually these are made of a soft dense foam. Other choices include Jay products, ROHO cushions and others. Your choice of cushion should be determined by the needs of your child. All cushions should provide the proper support, prevent skin breakdown and promote comfort. The cushion height must be considered when measuring the child for the seating system. Cut out portions can relieve tail bone pressure.

     

Anterior Trunk Supports:

    There are various types of supports made out of a variety of materials. Choice depends on the needs of the child. All children may be required to have one for school transportation. They should be used to promote upright mid line posture. They should never be attached to the seat belt.

     

Seat Belt:

    All seating systems should have a seat belt. They are designed either in a two or four point pull depending on the need for pelvic control. They may or may not be padded. Release may be either the standard airplane-type release or push button release. Choice depends on the child's needs.

     

Upper extremity support tray:

    The tray is usually made from a high density plastic or clear Plexiglas. Wood is rarely used anymore. It can be opaque, white, or clear depending on the need of the child. It may have raised edges to prevent objects from falling. It should fit snugly over the armrests and should be secured with either a Velcro or seat-belt like closure. The tray is used for arm support and may have elbow blocks attached to improve upper extremity position and function. It is useful for mounting computer or communication devices and for providing work space for the child.

     

Guidelines for the wheeled mobility bases:

    All bases should be monitored on a weekly basis for safety and to maintain proper function. If the base is modified by someone other than an authorized rehabilitation technician, then the warranty may be negated. Mobility bases should be chosen after the seating and positioning needs of the child are addressed. There are several types of mobility bases. Choice is dependent on the needs of the child and/or the caregiver.

 

Types of bases:

    Manual: May be propelled by the child with upper extremity control or by the caregiver using the push handles. It is the most economical choice.

    Power: Allows for independence for the more involved child. The drive wheel position determines the maneuverability and turning radius.

     Front-wheel drive may be difficulty to steer at high speed but allows for turning sharp corners easily.

     Mid-wheel drive has a smaller turning radius but may be less stable on uneven ground.

     Rear-wheel drive is better on uneven ground and at higher speed but they has a larger turning radius.

     

    Stroller bases: Used with children who are dependent upon others for mobility. They resemble a baby stroller with 4 smaller wheels. Mounting custom seating systems may prove difficult or impossible as the child grows and the needs change.

     

    Folding Frame:

     These are easily transportable but may require more maintenance. More complex seating systems are difficult to mount.

     

    Rigid Frame:

     The rigid frame is more durable and is capable of accepting custom seating systems. They are more difficult to transport. They provide a smooth ride on even ground.

     

    Reclining Back:

     Allows for changing the seat to back angle of the chair. This is advantageous for children who need to change position and rest during the day. Gravity assists with positioning. It is difficult to maintain the proper alignment of a custom back with changes in back angle. The positioning of the rear wheels makes it difficult for the child to self-propel the chair. The chair has a longer frame.

     

    Tilt-in-Space:

     Allows for proper alignment and positioning in the custom back while allowing for tilting to assist with pressure relief and gravity assist positioning. The size of the chair is generally deeper and higher and may be more difficult to transport.

     

Types of tires:

    Solid Rubber:

    These require no maintenance, are long wearing, less expensive and are good on indoor surfaces. They may be difficult to propel on uneven ground and have poor shock absorption.

     

    Pneumatic:

    These are air-filled tires requiring a tube. They provide a smooth ride with good shock absorption. They work well on uneven ground and are the lightest tire. They puncture easily and require maintenance to assure the proper amount of air.

     

    Semi-pneumatic with airless inserts:

    This is a hard rubber tire with either an air or foam filled insert. They are low maintenance and have better shock absorption than solid rubber tires although they are heavier.

     

     

Basic dimensional guidelines
for wheelchair accessibility in your home:

 

Passageways:

    Hallways: minimum of 36" wide

    Floor space: minimum of 30"x 48"

    Turning space: minimum of 60"

    Doorways: 32" to 36"

 

Heights:

    Door handles: 48" high

    Light switches: 15" – 48" high

    Tables and counters: 28" – 34" high

    Toilet height: 17" – 19" to top of seat

    Sink height: maximum height of 34"

 

Ramps:

    Slope: 1 to 12 ratio

    Width: 36" minimum

 

Choosing seating and positioning is a complex process. You should request input from a variety of sources, including the physical therapist, occupational therapist, speech therapist and teacher who works regularly with your child. These professionals give a perspective that might be overlooked by those doing the evaluation.

If your child wears orthotics of any kind, measurements should be taken with these on. If your child is scheduled for surgery, measurements should be taken after. If this is not possible, re-measurement should occur as soon as possible to insure seating meets positioning and safety needs.

You know your child best. Your input is extremely useful and should be valued. You might not be aware of all the pitfalls common to this endeavor.

 Your child should participate in as many decisions as possible.

 

Walking  versus  Wheelchair?

       Which One?

Bad question. Really. A common mistake, made particularly by schools, is to opt for a wheelchair over walking in order to "promote independence". Schools are not there to promote independence, that's what revolutions are for. Schools are supposed to promote learning. One thing kids need to learn is how to navigate a world most of which is, despite our best efforts, hostile to chairs.

Even when a chair is obviously the needed main mode of travel, confinement to only a chair, for children,  is generally a poor idea. Nearly half of all surgery performed on children with paralytic conditions is that of undoing the effects of growth complicated by prolonged sitting. They become the chair. Many kids are far better off in standing devices while in school rather than seated.

As kids get older and bigger, parents get older and weaker. The ability to merely one leg assist stand and pivot is valuable. Even poor stepping that takes it's own weight is rewarding to an adult who must rely on others. The difference between one person assisting and the requirement for two to lift is huge. So, a kid that forgoes standing and even primitive stepping skills because tooling around with a joy stick is such fun, is a set up for later woes. Then there is the weight gain. Oy.