Biomechanical modeling to prevent ischial pressure ulcers

Abstract

With 300,000 paraplegic persons only in France, ischial pressure ulcers represent a major public health issue. They result from the buttocks׳ soft tissues compression by the bony prominences. Unfortunately, the current clinical techniques, with - in the best case - embedded pressure sensor mats, are insufficient to prevent them because most are due to high internal strains which can occur even with low pressures at the skin surface. Therefore, improving prevention requires using a biomechanical model to estimate internal strains from skin surface pressures. However, the buttocks׳ soft tissues׳ stiffness is still unknown. This paper provides a stiffness sensitivity analysis using a finite element model. Different layers with distinct Neo Hookean materials simulate the skin, fat and muscles. With Young moduli in the range [100-500 kPa], [25-35 kPa], and [80-140 kPa] for the skin, fat, and muscles, respectively, maximum internal strains reach realistic 50 to 60% values. The fat and muscle stiffnesses have an important influence on the strain variations, while skin stiffness is less influent. Simulating different sitting postures and changing the muscle thickness also result in a variation in the internal strains.

Lateral pressure equalisation as a principle for designing support surfaces to prevent deep tissue pressure ulcers

“…The 3D model used here were important to support the conclusions drawn from 2D analyses, but there are also limitations to this model. While we have included more anatomical complexity including thighs, femurs and pelvis, more biofidelic models have been proposed (39)(40)(41). For example, we chose tissue mechanical properties in line with Oomens et al (14), but there are several published models of soft tissue mechanical properties that vary in complexity.…”

Gingival Embrasure Fill In Fixed Implant-Supported Prosthetics: A Review

“…A skin decubitus ulcer on the buttocks or ishium forms under surface pressure from a patient remaining in one position such as in a bed or wheel chair (22). There are internal strains in the skin, muscle and fat tissue from the surface pressure against underlying bone (23). Fat and muscle stiffness effects strain variations between the tissues (23).…”

“…Fat and muscle stiffness effects strain variations between the tissues (23). Skin is less influential (23). Tissue thickness also influences the development of decubitus ulcers (23).…”

“…Skin is less influential (23). Tissue thickness also influences the development of decubitus ulcers (23). Skin and mucosa are both epithelium and oral epuli may be related to decubitus ulcers.…”

Deformation of the gluteal soft tissues during sitting

“…Soft tissue deformation, during sitting, has been studied using finite element (FE) modelling (Lim et al, 2006(Lim et al, , 2007Linder-Ganz and Gefen, 2004;Linder-Ganz et al, 2009;Makhsous et al, 2007) and/or experimental methods (Linder-Ganz et al, 2007Sonenblum et al, 2013;Then et al, 2007) in an attempt to understand the aetiology of pressure ulcers (Olesen et al, 2010;Stekelenburg et al, 2008), or to improve the designs of seats and wheelchairs (Luboz et al, 2014). FE models can provide valuable insight to the condition of internal soft tissue structures under sitting loads (Sonenblum et al, 2013).…”