Finite Element Analysis of Contact Pressures between Seat Cushion and Human Buttock-Thigh Tissue

Abstract

Unrelieved pressure on load-bearing muscle tissues of humans can produce pressure ulcers. In a seated upright posture, the highest pressures occur inferior to the ischial tuberosities (ITs). Moreover, the vibration can initiate the development of pressure ulcer. Therefore, the seat cushion is not only used to lower the maximum seating pressure on buttocks but also minimize the transmission of vibration to human body. The purpose of this study was to investigate the effects of varying vertical vibration frequencies on seat-interface contact pressure during sitting on three different seat cushions by using a finite element modeling approach. A simplified two-dimensional human buttock-thigh model was developed to simulate the mechanical response of the muscle of buttocks and thigh under vertical vibration. Static and vibrational loads with five different frequencies of 0.1, 1, 10, 30 and 50 Hz and the same amplitude of 3 mm were applied to different seat cushions. The result showed that the "SAF 6060" seat cushion with both hyperelastic and viscoelastic behaviors could be effective in reducing the amplitude of varying maximum contact pressure, especially for the frequency of 10-20 Hz. This method could help in design of seat cushions with appropriate material properties and shape so as to reduce vibrations transmitted to human body at a certain frequency range.

A Comprehensive Literature Review of the Pelvis and the Lower Extremity FE Human Models under Quasi-static Conditions

“…The studies listed in the final literature list for this review showed a variation in the gender and percentile of the model developed during each study. However, out of the fifteen studies six did not specify the gender and the percentile of their model (Camacho, Ledoux et al 2002;Mattingly, Talwalkar et al 2006;Martins, Pato et al 2007;Shim, Pitto et al 2007;Makhsous and Lin 2009;Tang, Chan et al 2010), three studies developed subject-specific models based on data obtained from male subjects (Phillips, Pankaj et al 2007;Wagnac, Aubin et al 2008;Bai, Wei et al 2010 (Cheng, Smith et al 2007;Silvestri and Ray 2009) and two developed models to represent three percentiles (5 th percentile female, 50 th percentile male and 95 th percentile male) (Vezin and Verriest 2005;Kim, Pyun et al 2010).…”

“…The literature review identified three studies to have obtained their data from cadavers (Camacho, Ledoux et al 2002;Anderson, Peters et al 2004;Martins, Pato et al 2007) and five studies obtained their data from live subject scans (X-ray scans (Vezin and Verriest 2005), 3D scans (Phillips, Pankaj et al 2007), MRIs (Mattingly, Talwalkar et al 2006;Makhsous and Lin 2009), and CT scans (El-Asfoury and El-Hadek 2009)). The remaining study did not specify the source of their data (Tang, Chan et al 2010).…”

“…Examination of the fifteen studies showed that out of the total fifteen studies, six did not specify a posture for the model (Camacho, Ledoux et al 2002;Martins, Pato et al 2007;Shim, Pitto et al 2007;El-Asfoury and El-Hadek 2009;Silvestri and Ray 2009;Bai, Wei et al 2010), three models were developed to represent a human in a seated posture (Vezin and Verriest 2005;Cheng, Smith et al 2007;Tang, Chan et al 2010), one study specified a nonweighted sitting posture for the subjects while the data was collected (Wagnac, Aubin et al 2008), one specified a driving posture (Kim, Pyun et al 2010), while Makhsous et. al (Makhsous and Lin 2009) specified that subjects were sitting with an 80 degree flexion of the hip and a 90 degree flexion of the knee under two different loading conditions, a simulated sitting pressure (in an closed MRI scanner, the pressure was simulated by placing a cushion under the buttock of the subject) and a nositting pressure (in an open MRI scanner, the subject was upright-seated and underarm supports were placed to bear the weight of the subject) .…”

Pressure sores of human tissue damage during pelvic binder compression

“…Alternatively, cadavers could be acquired; however, they are very expensive. Therefore, the deformation and subcutaneous stress of tissue between tissue interactions could not be observed [9]. Thus, the finite element (FE) modelling should be conducted to find the behaviour and the effect of tissue mechanical response against PCCDs.…”

“…Thus, the finite element (FE) modelling should be conducted to find the behaviour and the effect of tissue mechanical response against PCCDs. FE simulation of tissue interactions was carried out by researchers to study the effect of contact pressure on tissue interfaces [9][10][11][12][13][14][15][16]. Based on these studies it showed that there were many factors influencing pressure on tissue interactions, such as geometry, material model, boundary conditions and applied load.…”