The influence of backrest inclination on buttock pressure

To assess the effects of backrest inclination of a wheelchair on buttock pressures in spinal cord injured (SCI) patients and normal subjects.

The participants were 22 healthy subjects and 22 SCI patients. Buttock pressures of the participants were measured by a Tekscan® pressure sensing mat and software while they were sitting in a reclining wheelchair. Buttock pressures were recorded for 90°, 100°, 110°, 120° and 130° seat-to-back angles at the ischial tuberosity (IT) and sacrococcygeal (SC) areas. Recordings were made at each angle over four seconds at a sampling rate of 10 Hz.

The side-to-side buttock pressure differences in the IT area for the SCI patients was significantly greater than for the normal subjects. There was no significant difference between the SCI patients and the normal subjects in the buttock pressure change pattern of the IT area. Significant increases in pressure on the SC area were found as backrest inclination angle was changed to 90°, 100° and 110° in the normal subjects, but no significant differences were found in the SCI patients.

Most of the SCI patients have freeform posture in wheelchairs, and this leads to an uneven distribution of buttock pressure. In the SCI patients, the peak pressure in the IT area reduced as the backrest angle was increased, but peak pressure at the SC area remained relatively unchanged. To reduce buttock pressure and prevent pressure ulcers and enhance ulcer healing, it can be helpful for tetraplegic patients, to have wheelchair seat-to-back angles above 120°.