Influence of sacral sitting in a wheelchair on the distribution of contact pressure on the buttocks and back and shear force on the ischial region

Abstract

[Purpose] The purpose of this study was to investigate the influence of sacral sitting in a wheelchair on contact pressure on the buttocks and back, and shear force on the ischial region. [Subjects and Methods] Twenty-six healthy adults assumed two postures while seated in a wheelchair: a basic sitting posture, and sacral sitting with the pelvis tilted posteriorly and the ischium slid forward by 5 cm relative to its position in the basic sitting posture. The inclination angle of the sagittal pelvic line, contact pressures and contact areas on the buttocks and back, and the shear force generated by sliding the ischial region forward were measured. [Results] Posterior pelvic tilt was significantly greater during sacral sitting. Maximum contact pressures on the buttocks and ischial region were significantly lower during sacral than during basic sitting. However, maximum contact pressure on the back, the contact areas of the buttocks and back, and the shear force generated by sliding the ischial region forward were significantly greater during sacral sitting. [Conclusion] Sacral sitting in a wheelchair increases the maximum contact pressure on the back, contact areas of the buttocks and back, and the shear force generated by sliding the ischial region forward.

Quantitative Measurement of the Pressure and Shear Stress Acting on the Body of a Wheelchair User Using a Wearable Sheet-Type Sensor: A Preliminary Study

“…Furthermore, researchers have reported that when a shear force is high, vascular occlusion occurs at half the pressure of a low shear force, resulting in the viewpoint that this shear force is a more important factor [ 11 ]. This suggests that the effect of shear forces on the obstruction of blood flow may be a significant factor in pressure ulcers, and efforts have been made to determine the effect of shear forces acting on the buttocks of wheelchair users [ 12 , 13 , 14 , 15 ]. However, one problem in the way of research progress is the difficulty in measuring shear force in wheelchair users, compared with pressure.…”

Development of Hybrid Three-axis Load Sensor

“…After this discovery, several research groups tried to evaluate the shearing force applied to the buttocks placed on a wheelchair. (6)(7)(8) For example, Kobara et al used a kind of force plate to measure the total shear force applied to the entire seating surface of a wheelchair. (7) Recently, we developed a shear force sensor to evaluate the local shear force in different postures, and found that regardless of posture, a backward-directed shearing force occurred below the ischial tuberosity in seated positions.…”