Seat Angles and Support

To the Editor: The article by Shields and Cook (November 1988) comparing the effects of lumbar support and seat angles on buttock pressure was nicely done and appropriately demonstrated those effects. My own investigations into seat design to decrease pressure on the ischial tuberosities have led me to the use of a cushion (usually a high-density polyurethane pad about 14 to 16 in long × 8 to 9 in wide × 1 to 1.5 in high), which is placed across the front part of the seat so that the ischial tuberosities rest just off the posterior aspect of the cushion. This shifts the concentrated pressure from under the ischial tuberosities and distributes it over a broader area under the upper thighs. Skin shear is decreased, and the pelvis is anchored posteriorly in the chair, making the backrest more effective.

ARTICLE