Prevention of Sliding in Seated Mobility, Part 1

Hello all!

This month, I would like to focus on the prevention of sliding from a wheelchair. I will talk about the effects of sliding and the common "quick fixes" and why they do not work. Next month, I will review how understanding the cause of sliding helps to find the true solution. I will discuss features of generic seating and wheelchair configuration that may assist in preventing sliding.

The harmful effects of sliding in a wheelchair are numerous. Sliding results in poor positioning for a person that then can limit function for that individual. Remember, we need proximal stability for distal function. When sliding occurs, stability may be diminished and upper extremity function may be compromised. In addition, physiological functions, such as respiration and digestion, may be affected if the person slides into posterior pelvic tilt. Sliding in a wheelchair also brings with it the risk of shear and skin breakdown. (Please refer to my posting on Pressure Sores and Skin Protection for a definition of shear.)

Sliding from a wheelchair causes increased care giving needs if a person is unable to reposition himself/herself, as caregivers respond to the need to reposition a person to a more upright position.

Sliding in a wheelchair brings with it the risk of injury and falls. Think of Newton's First Law of Motion. Recalling high school physics, remember that a body at rest tends to stay at rest while a body in motion tends to stay in motion, unless a force is applied to it. If a person begins sliding in a wheelchair, the person may continue to slide and fall out of the wheelchair, with the potential for injury to occur.

Because of the harmful effects of sliding, solutions to prevent sliding are sought. Sometimes the solutions are "quick fixes" that do not address the cause of sliding, but rather provide a "bandage" solution. Because it is a bandage solution, these tend not to work in the long term. Some of these "solutions" include the following: wedge cushion; elevating leg rests; abduction pummel; non-slip mat on top of the cushion; and positioning belts.

The presumed rationale behind the use of a wedge cushion is that by decreasing the hip to back angle to less than the typical 90 degrees, the pelvis will be held in position at the back of the wheelchair. That is, the pelvis will be "wedged" into position on the wheelchair. Does this work? If a person has insufficient hip range of motion to tolerate this position, the person will continue to slide into a posterior pelvic tilt to relieve the discomfort caused by squeezing the hips and pelvis into a position that cannot be tolerated. In this case, the wedge cushion will not work to prevent sliding and may cause other problems, such as shear.

The presumed rationale behind the use of elevating leg rests to prevent sliding is that by raising the legs, the feet provide a "block" to prevent sliding and help to position the pelvis at the back of the wheelchair cushion. Does this work? Stretching the legs to prevent sliding does not work. If, for example, a person has tight hamstrings, extending the legs will cause the person to slide into a posterior pelvic tilt to relieve the discomfort that the over-stretching has caused as the hamstrings attach to the back of the knee and the pelvis.

Sometimes an abduction pommel may be used to minimize the effects of sliding. The rationale is that the pommel provides an end point to prevent a person from sliding completely off a cushion. A pommel, however, does not prevent sliding. Going back to Newton's First Law of Motion, a pommel only provides a force to stop a body in motion (i.e. sliding). Think about how uncomfortable it must be to slide into a pommel and to remain seated at that pommel until repositioning occurs. An abduction pommel should be used for positioning to align the heads of the femurs with the acetabulum; it should not be used to prevent or limit sliding.

Another "solution" is to apply a non-slip mat on top of a cushion to prevent a person from sliding in the wheelchair. The thought is that the friction inherent in the non-slip material will prevent a person from sliding. Does this work? Applying a non-slip mat to a cushion to prevent sliding is a "quick fix" and does not address the cause of sliding. If the cause of sliding for an individual was addressed, rather than using a bandage solution, there should be no need for a non-slip mat. In addition, when a seating manufacturer designs a pressure relieving cushion, the intention is that a person will sit directly on the cushion cover to allow immersion and envelopment to occur, rather than having an additional layer between the person and the cushion which may limit the effectiveness of the cushion's properties.

Finally, sometimes the temptation is to use a positioning belt to prevent sliding. Does this work? Like other bandage solutions, the use of a positioning belt will not prevent sliding. If the cause of sliding in a wheelchair has not been addressed, a positioning belt will not work to prevent sliding; a person will slide into, or under, a positioning belt and be at risk for injury. The true purpose of a positioning belt is to stabilize the pelvis after seating and wheelchair configuration has been optimized for a person's presenting posture. Thus, a positioning belt has its place in seating and mobility prescriptions, but not as a means to prevent sliding.

This month, we have looked at the effects of sliding and some common "quick fixes" that are used to address sliding. We have seen that the quick fixes tend not to work as they do not address the cause of sliding. Next month, we will look at some of the common musculo-skeletal factors that influence the potential for sliding and will see that by understanding the cause of sliding, we can find the true solution.

References

1. Batavia, M. (2010). The Wheelchair Evaluation. A Clinician's Guide. (2nd ed.). Sudbury, MA: Jones and Bartlett Publishers
2. Cooper, R. (1998). Wheelchair Selection and Configuration. New York: Demos Medical Publishing
3. Jones, D. (1995). Real Solutions. Downloaded from https://www.wheelchairnet.org
4. Rader, J., Jones, D., and Miller, L. (N.D.) Individualized Wheelchair Seating for Older Adults. Downloaded from http://www.primaris.org