In the world of wheelchair seating and positioning, we do not have a single consensus of what a neutral seated posture looks like. The seated posture is also influenced by the task at hand. We sit very differently if we are typing at our desk vs. watching a football game on the couch. Most of us move in and out of various positions throughout our day. For the wheelchair user, a single position has to provide postural support for stability, function, and alignment; provide a position of rest; and distribute pressure to maintain comfort and reduce pressure risk as frequent positional changes may not occur.
A primary goal of positioning is alignment. However, not all people who use wheelchair seating can be aligned to a neutral posture. A client may have an asymmetry which is reducible, partially reducible, or non-reducible. These ‘asymmetries’ are sometimes referred to as orthopedic deformities. This is not a desirable term and does not adequately define the problem.
Many asymmetries we see in positioning are reducible (also referred to as flexible), meaning that we can correct the asymmetry to neutral. For example, if a client sits with a 20-degree lateral scoliosis which can be reduced to neutral with appropriate positioning, this is called a reducible asymmetry. The goal of positioning a reducible asymmetry is a correction. With that said, we may choose not to fully correct a client’s position to neutral under several circumstances:
• Range: we don’t want to place muscles on full stretch to achieve symmetry. This can be painful, lead to tissue damage, and elicit a stretch reflex which makes the muscle tighter.
• Pain: If full correction leads to client discomfort, back off a bit.
• Pressure: If full correction requires excessive pressure, this pressure can either be redistributed (i.e. molded seating vs. other options) or the seating system may be configured to allow a slight asymmetry to reduce pressure.
Partially Reducible Asymmetries
An asymmetry may be partially reducible. Using the above example of a client sitting with a 20 degree lateral scoliosis, the asymmetry may only be able to be reduced to 10 degrees. Part of the asymmetry is reducible, and part is not. It is important to reduce the asymmetry as much as possible to prevent the reducible portion of the curvature from becoming non-reducible.
If that scoliosis cannot be reduced at all, this is a non-reducible (also referred to as fixed) asymmetry. This may be due to range of motion limitations caused by shortening of soft tissue or orthopedic changes. Non-reducible asymmetries can worsen but will not generally improve without medical intervention. These interventions may include prolonged stretching, tone reducing injections, or surgery. The goal of positioning a non-reducible asymmetry is accommodation. Molded seating may be required to provide adequate postural support and pressure distribution. Adequate accommodation may slow the progression of the asymmetry.
It is critical to understand the reducibility of postural asymmetries in order to make the most appropriate seating recommendations. Asymmetries are best analyzed during the mat exam.
Michelle L. Lange, OTR/L, ABDA, ATP/SMS