January/February 2006

Pediatric Seating and Support

By Ginny Paleg, PT

The proper seating system enables mobility, support, and the preservation of skin integrity.

Implementing a good seating system early in a child’s development helps build strength and better posture.

SKIN INTEGRITY CONSIDERATIONS

The first thing to do is assess the risk: minimal, moderate, or severe. Because Makayla is mobility impaired (she cannot do an effective independent weight shift) and sensory impaired, her skin risk is severe. This means we have to provide an appropriate cushion, a chair with tilt (at least 45 degrees), and a weight-relief program. In cushions, we have to choose between fluid, solid materials, or a combination. Air, flowing gel, or any medium that flows would be considered a fluid/liquid. These materials are often the best for reducing shear and peak pressures. By themselves, however, they are often unstable as a support surface for sitting. Foam, nonfluid gel, plastic cells, and similar products that do not “flow” when you cut them are solids. These solids are the most stable material and offer the greatest pelvic stability when sitting. There are also products that combine these two mediums. In these systems, the fluid medium is beneath the bony prominences for the purpose of shear and pressure reduction, and the solid material provides support for the femurs all the way from the trochanter to the back of the knee, encouraging both skin protection and pelvic stability. When thinking about the person who is at the highest level of risk versus the person at moderate risk, it is critical to consider the depth of immersion that is offered for the bony prominences such as the ischium. When one considers the height difference between the ischials and the trochanter, it becomes evident that for a mature pelvis, one would need at least a 2 inch depth (1 inch for a child of Makayla’s age) of immersion capability to avoid bottoming out.

POSTURE FOR FUNCTION CONSIDERATIONS

Pelvis
The most important lesson is—respect the anatomy.

If we were to sit with all our load on the ischials and/or sacrum, it would be uncomfortable as well as result in skin breakdown. The goal is to maximize surface contact area and reducing the work of sitting—the common practice is to load the femurs, all the way from the trochanter to the back of the knee, the feet, the lumbar thoracic intersection, as well as the occiput area if necessary. We also need to capture the pelvis from a posterior lateral aspect if our goal is to stabilize it. This is usually done by supporting the pelvis at approximately the level of the PSISs. Lastly, be careful with pelvic straps. Lots of pressure across the ASIS in children under the age of 5 years may actually lead to deformities as the constant abnormal loading does not allow the pelvis to open (as it does in normal development) and this may contribute to hip subluxation.

By supporting, respecting, and loading the various anatomical structures, we provide stability and balance for function.

Spine
Stack the vertebra and respect the curves.

All children with spinal cord injuries are at the highest level of risk for scoliosis. By supporting age-appropriate curves, we may be able to slow down or correct a flexible deformity. Most published studies show that just a few degrees (5 to 15) of tilt allow the curves to be supported. In a contoured system, it is easier to fight the effect of gravity on the spine of a child with a spinal cord injury. The key is to respect the posterior flare of the sacrum. When the pelvis can achieve a “neutral” position, support the posterior-lateral pelvic area and load the lumbar/thoracic intersection and thoracic area. A lot of contour behind the lumbar curve can actually push the child forward and encourage a collapsed posture.

Head
If head control is still a challenge in sitting, after the pelvis and spine have been supported/accommodated, load the occipital (nucal) ledge. Use a headrest that comes under the skull and supports the head against gravity. Make sure the child can maintain an open airway (slight extension) without a lot of jaw thrust. If posterior support is not enough, using lateral supports on the jaw bone and skull can also help keep the eyes and head in good alignment without having the child work too hard against gravity. Remember that straps are for assisting gravity, never to fight gravity. Straps alone cannot hold a child’s body up against gravity. Anterior strapping can at times be necessary for feeding and other short time activities in conjunction with all of the parameters previously discussed.

Hips
Start with a thorough assessment. Make sure the child is able to tolerate 90 degrees of true hip flexion in the absence of posterior pelvic rotation. The reason this is so important is because most wheelchair seating systems come out of the “box” configured with a seat-to-back angle of 90 degrees. If the client does not have that range, then the system will force the client to sit with a posterior rotated pelvis and a compensating “collapsed posture.” By knowing this information ahead of ordering the equipment, a seat-to-back angle other than 90 degrees can be requested. If an antithrust shelf is being used, check that it is not so contoured that it is increasing hip flexion. If it is,, then make sure the child can actually achieve this amount of hip flexion without posterior pelvic rotation and flattened lumbar spine. I have often made the mistake of increasing hip flexion to decrease extension tone only to find the child struggles even more and my seating is even less effective. This is usually because a hip has begun migrating out of the socket (acetabulum) and the child is uncomfortable with hip flexion and scoots forward or rotates the pelvis to open the hip. If I had paid attention and taken the time to realize this sooner, we all would have been happier with a more successful outcome.

The hip is not finished forming when the child is born. The growth plate is open, and the femoral head is floating on cartilage. The femoral neck is almost straight, and there is no angle (anteversion/retroversion). The acetabulum is very shallow. It is through weight-bearing and active muscle contraction (gluteus medius is the key muscle) that the femoral neck begins to angle and rotate and the acetabulum deepens. For a child with a spinal cord injury, the bone is most likely osteopenic, and the integrity of the hip may be compromised and prone to subluxation or dislocation. The best way to maintain the structure and joint integrity as well as bone density is to have the child participate in an EMG-assisted activity program. Some studies are being conducted on this using a body-weight support harness over a treadmill. The initial data looks promising. For now, the best evidence-based approach would be a passive standing program. The child should be placed in a stander for 60 to 90 minutes every day. The time can be broken up into two or three 20-minute increments. For our case study, 8-year-old Makayla had some use of her arms. To encourage strengthening of her accessory breathing muscles, we chose a stander with large wheelchair-type wheels that she could push. Makayla also enjoyed the freedom of moving around her classroom and keeping up with her friends. For a child with a higher or more complete injury, a few companies make standers that drive like power wheelchairs. You can use a joystick or switches.

Knees
Like many children with spinal cord injuries that spend most of their time sitting and have mild to moderate spasticity, Makayla has tight hamstrings. While it may seem enticing to try to stretch the hamstrings while she is in the chair through the use of elevating legrests, STOP! DON’T DO IT! Never use elevating legrests to stretch tight hamstrings. The child will merely externally rotate and flex to avoid the pain. Elevating legrests can’t even help with edema unless they are combined with tilt so that the feet are elevated above the level of the heart. The best approach for Makayla will be to wear long leg splints or knee immobilizers (with her ankle-foot orthoses on) while she sleeps. Research has shown that it takes 6 hours to adequately stretch spastic muscles. The hamstrings are a two-joint muscle. They are best stretched when the hip is flexed and the knees are extended. A long leg sitter proved helpful for Makayla to get a stretch on her hamstrings during the day. We had to start gently, allowing lots of knee flexion and stopping external rotation. Some kids may even need to start with a bit of knee flexion and hip extension to be able to tolerate this position.

Feet
Choosing the right footrests/footplate can be like playing darts in the dark. The shoe may look great—flat and well supported—but inside the foot may be twisted and plantar flexed. The secret is to look at the child barefoot or in their brace and make the footrest/footplate angles and orientation match their foot/ankle/knee alignment rather than making their foot look like the footplate. When ordering the chair, get an angle-adjustable and rotational footplate so that you can angle it in space and accommodate whatever comes along.

Toileting
When Makayla does her bowel and bladder program, we need to make sure that she is provided with a system that provides adequate support and postural alignment, has adequate cushioning to preserve skin integrity, and facilitates function (self-catheterization and privacy while waiting for elimination). The same principles as for wheelchair seating apply here. Footrests at the correct angle and orientation are essential so the feet can be loaded. Most children need to have some forward leaning in order to have a successful bowel movement. A tray (upper extremity support) may be key to helping the child relax enough and still lean forward.

Bathing
There are two approaches to bathing: active versus passive sitting. If the child wants to play in the tub, they need to be sitting upright. There are some bath supports that allow this. If you choose this approach, a wraparound trunk support and well-placed piece of Dycem can allow for function and access to the areas that need to be washed.

If you pick a bath chair that enables the child to lie almost flat on their back, make sure the material has some give and is not damaging to the skin.

In conclusion, a good seating system begins with a good base. Make sure you respect the anatomy, load strong areas, and support weak segments. If the child fits well and can hold their head and spine in alignment, you are probably on the right track!

Ginny Paleg, PT, is an NDT-certified pediatric physical therapist in Silver Spring, Md. She splits her time between the Montgomery County Infants and Toddler Program and teaching continuing education programs. She is currently a DScPT student at the University of Maryland in Baltimore, as well as the reimbursement chairman for the Pediatric Section of the APTA. Paleg can be contacted at

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