Force on the sacrococcygeal and ischial areas during posterior pelvic tilt in seated posture

Abstract

Background: Most posture problems encountered in persons who use wheelchairs in a seated posture for extended periods are related to sacral sitting due to posterior pelvic tilt. Posterior pelvic tilt places pressure and shearing force on the sacrococcygeal area that can lead to pressure ulcers, but the relationship between pelvic tilt and force applied to the sacrococcygeal and ischial tuberosity areas has not yet been investigated. Objective: To investigate the relationships of posterior pelvic tilt in a seated posture with vertical force and horizontal force on the sacrococcygeal and ischial tuberosity areas. Study Design: Repeated measures design. Methods: Thirty male and female subjects aged ≥60 years sat in a measurement chair at varying pelvic tilt angles, and force on the sacrococcygeal and ischial tuberosity areas was measured. Results: The pressure on the sacrococcygeal area increased with pelvic tilt in all subjects, with vertical force averaging 19% of the body weight at a pelvic tilt angle of 30°. The horizontal force on the sacrococcygeal area increased in 93% of the subjects, with an average increase equal to 3% of the body weight. Conclusions: We confirmed changes in vertical and horizontal forces on the sacrococcygeal and ischial tuberosity areas with a change in seated posture (pelvic tilt). Clinical relevanceWe propose guidelines for rehabilitation practitioners working with wheelchair users to suggest improved ways of sitting in wheelchairs that avoid pelvic tilt angles that might promote pressure ulcers on the buttocks.

The Effects of Combined Trunk and Gluteal Neuromuscular Electrical Stimulation on Posture and Tissue Health in Spinal Cord Injury

“…Poor sitting postures cause redistribution of loads acting through the pelvic region. During sacral sitting, the lumbosacral and pelvic regions experience greater loads, increasing regional interface pressures (IPs) [14]. Normal sitting posture is generally assumed to be symmetrical with equal loads acting bilaterally through the ischia.…”

Influence of Leg Support Elevation on Horizontal Force Acting on the Buttocks in a Reclining Wheelchair in Different Rotational Axis Positions of the Back Support

“…The North American National Pressure Ulcer Advisory Panel [14] defines "shear" as "an action or stress resulting from applied forces which causes or tends to cause two contiguous internal parts of the body to deform in the transverse plane. " As measuring shear force is difficult, we measured the horizontal and normal forces to determine the shear force as in the previous study by Kemmoku et al [12]. The horizontal and normal forces acting on the buttocks were measured using a force plate (400 x 400 mm; sampling frequency, 100 Hz; Kyowa Electronic Instruments, Tokyo, Japan) that measured the reaction force in the posterior direction, which is equivalent to the horizontal force in the anterior direction while the back support is inclined.…”

“…The participants were instructed to fold their arms in front of their chests in a relaxed state and to not intentionally change their body position during the experiment. Kemmoku et al [12] reported that the vertical and horizontal forces acting on the sacrococcygeal and ischial tuberosity areas increase in a seated posture as the angle of pelvic tilt increases. Thus, to ensure consistency in the pelvic tilt angle, each participant's buttocks were positioned so that their dorsal surface was in contact with the back support.…”

“…Aissaoui et al [9] reported that the pressure on the back support while sitting on a chair increased by elevating the leg supports. Moreover, Kemmoku et al [12] reported that the horizontal force acting on the sacrococcygeal and ischial tuberosity areas while seated increases as the pelvic tilt angle increases. In addition, our previous study reported a strong relationship between the reaction force on the back support and the horizontal force acting on the buttocks [17,18].…”

Feasibility of closed-loop controller for righting seated posture after spinal cord injury

“…The inability to control the motions of the spine and pelvis can severely compromise upper-limb workspace [1], increase the risk of pressure sore development [2], and adversely affect manual wheelchair propulsion and completion of many activities of daily living [3][4]. Because of this, individuals with SCI rank restoration of trunk stability as one of the highest priorities to enhance quality of life, regardless of injury level [5].…”