ARATA 2014 National Conference – Actively Choosing Technology
Selecting Appropriate Seating for Wheelchair Users:
Science and Practice.
Bjornson, A
This workshop will examine the major conceptual trends of seating. The
science of seating will assist in appropriate selection and prescription of
wheelchair seating. We will look at design technology of cushions and
apply it to the principles of pressure relief and postural support.
Many factors contribute to pressure ulcer formation including nutrition,
age, hydration, body heat management, incontinence, posture, smoking
status, co-morbidities, shear and pressure. These can be categorized
into external and internal factors. Our cushions are designed to deal
with the external factors, primarily pressure, posture and shear.
The means by which these forces are managed form a substantial part of
pressure ulcer prevention and treatment. Therefore cushions are
prescribed according to their abilities to distribute load thereby
maintaining tissue integrity. This workshop explains cushion design in
terms of load placement and management, use of materials to
distribute load and use of surface shapes to promote good sitting
Load Placement and Management
• Load the ishials and trochanters, redirect load to the thighs
• Anterior contour to facilitate thigh loading
• Lateral contour to provide lateral stability and trochanteric loading
Materials to Distribute Load
• Use fluid under ischials to immerse – hydrostatically load
• Use different density/type of foam under ischials to envelop
Quantifying the effect:
• Immersion: capability of a cushion to allow the body to sink into it
• Envelopment: capability of cushion to deform around and
encompass the shape of the body.
• Magnitude: the force that is concentrated on the bony
Materials to Affect Posture
Positioning is the ability to control shape to accommodate or correct
• Anterior contour: affects loading and A/P pelvic stability/position
• Lateral contour: affects loading and lateral pelvic stability /position
• Positioning components: aid in creating contours, addressing postural
1. Pressure Ulcers in Adults: Prediction and Prevention.No 3. Clinical Practice
Guideline. Rockville, MD: Agency for Health Care Policy and Research; May
1992. AHCPR publication 92-0047.
2. Bergstrom N, Braden B, Boynton P, Bruch S. Using a research-based
assessment scale in clinical practice. Nurs Clin North Am. 1995;30(3):539550.
3. Springle, S. Effects of Forces and the Selection of Support Surfaces Topics in
Geriatric Rehabilitation, December 2000, 16:2 47-60