POSTURE EFFECT ON SEATING INTERFACE BIOMECHANICS - COMPARISON BETWEEN2 SEATING CUSHIONS

Objective: This study aimed at investigating the effects of sitting po sture on ischial pressure and pelvic orientation for two types of cush ions. Design: Two types of seating devices, Roho and Polyurethane (PU) Foam cushions, six predefined postures, and two subject groups, Norma l and Paraplegic, were tested. Ischial pressure and pelvic orientation were monitored. The sequence in which the cushions were tested were r andomized, and the postures were tested according to a preplanned sequ ence. Setting: The experiments were carried out in the laboratory of a rehabilitation engineering centre in Hong Kong. Participants: Six par aplegic subjects (referred sample) and 8 normal volunteers were tested . At the time of study, no subjects showed any signs of pressure sore or other health problems. Main Outcome Measures: It was hypothesized t hat sitting posture could significantly affect pelvic orientation as w ell as pressure distribution. It was also hypothesized that cushion se lection was a critical factor in compensating the adverse effects of p ostures on pressure distribution. Results: With the paraplegic group, the maximum ischial pressure recorded on Roho for various postures ran ged from 88mmHg for the Trunk-Bent-Forward (PF) posture to 146mmHg for the Trunk-Bent-Right (PR) posture, whereas on PU foam cushion, the va lues ranged from 106mmHg for the PF posture to 221mmHg for the PR post ure. With the paraplegic subjects sitting with their bunks bent latera lly, it was found that the mean pressure difference between the left a nd right ischial tuberosities was more prominent on the PU foam cushio n than on the Roho. Conclusion: Sitting posture can significantly affe ct pelvic orientation and ischial pressure. This study also showed tha t the Roho cushion was significantly more efficient in compensating th e adverse effects of sitting posture on pressure distribution. (C) 199 6 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation