Analysis of Body Slip and Seat Pressure in Powered Wheelchairs with Two-Slide Recline System

Recline and tilt functions are the most desirable features for relieving seating pressure to decrease the risk of pressure ulcers. This study presents a new recline mechanism for a powered wheelchair for users sitting for a long duration. We analyzed the effect of a developed two-slide mechanism. In this study, body slip distance and buttock pressure were measured during wheelchair reclining and repositioning using a three-dimensional motion analysis and a pressure measurement system in 10 healthy subjects. Non-slide, one-slide, and two-slide versions were compared. During reclining, the total slip distance along the backrest with two slides was 40.6 mm, which was 77% and 44% smaller than non-slide and one-slide backrests, respectively. The slip variation of the non-slide was 38 mm at the beginning of recline in the initial seated position, and the slip distance tended to decrease as the recline angle increased. However, in the two-slide backrest, the average slip distance per 10° interval was only 5.1 ± 1.1 mm. In addition, we observed a similar slip in repositioning as in reclining, and the slip distance along the seat also decreased most in the two-slide backrest. The buttock pressure gradually decreased from 100° to 150° and then increased again from 160°, but the two-slide backrest showed a tendency to decrease at larger angles of recline and decreased by 59% of the maximum pressure. This study confirms that the two-slide system reduces body slip and buttock pressure, and it is expected that risk factors caused by the long-term use of a wheelchair can be minimized.