PhD defense of Ekaterina MUKHINA on 11/25/22

PhD defense of Ekaterina MUKHINA of BIOMÉCA team on november, the 25th at 2pm:

« Experimental and numerical approach

for the biomechanical modeling of the sacral soft tissues

in the context of pressure ulcer prevention »

bullet Jury :

  • Yohan PAYAN, Director of Research, CNRS - Supervisor
  • Xuguang WANG, Director of Research, Université Gustave Eiffel - Reviewer
  • Stéphane AVRIL, Professor, École des Mines de Saint-Étienne - Reviewer
  • Hélène PILLET, Professor, ENSAM Paris - Examiner
  • Céline FOUARD, Assistant professor HDR, Université Grenoble Alpes - Examiner


bullet  Keywords:  

Finite element model; Mechanical properties and medical imaging; Materials engineering

bullet Abstract:

A Pressure Ulcer (PU) is defined, according to National and European Pressure Ulcer Advisory Panels (NPUAP and EPUAP) as: “a localized injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear.” According to epidemiology studies, a PU is a complication primarily related to the care and treatment of individuals who have difficulty moving or changing positions: based on the study conducted in hospitals from five European countries, a PU prevalence of 18% was observed (Vanderwee et al. 2007).
In the worst case, untreated PU or its complications could lead to death; from 1999 to 2016 in Spain, PU was listed as a cause of death for 11238 people over 65 years old (Verdú-Soriano et al. 2021). PUs also have an important impact on the psychological state of the person affected (Upton and South 2011). They can potentially lead to social isolation and worsening of the existing medical condition.
The clinical management of PUs also represents a financial burden for society. A study by Dealey et al. estimated that the cost of PU treatment in United Kingdom could be as high as £14108 for a grade 4 PUs (Dealey et al. 2012). Meanwhile, the latest research by Downie et al. (Downie et al. 2013) based on a 12 months-long study in five UK hospitals suggests that 43% of the grades 3 and 4 PUs could be preventable.
Current research oriented on the development of PU prevention strategies includes the development of new risk assessment protocols, sensors, research on pressure injury biomarkers, and mechanical parameters that could help in the decision-making process. It has been shown, in a rat model, that there exists a correlation between compression-induced tissue damage and mechanical strain (Ceelen et al. 2008). Based on this evidence, several numerical models, mostly based on Finite Element Analysis, have been proposed in the literature to estimate tissue deformations resulting from the mechanical interaction of the body with external devices. Moreover, according to figures reported in a National Prevalence Study in French Hospital patients, sacral 29% and heel 53% regions have been reported to be the two most common anatomical sites for PU development (Barrois et al. 2008). Sacrum was therefore chosen in this study as the investigation location.
As shown in several studies, the mechanical response is very sensitive to the input data (geometry (Moerman et al. 2017), material properties (Luboz et al. 2014), and boundary conditions). Building patient-specific mechanical models for the prediction of strain localization is a long and tedious task but seems necessary to accurately evaluate the risk factors. It is clear that to bring the research findings to the clinical environment, an accessible minimally time-consuming technique should be employed. 3D MRI is often considered a benchmark technique for collecting the geometrical data of Finite Element (FE) models, but it remains a costly and not easily accessible exam. On the other hand, 2D B-mode Ultrasound (US) was investigated as a promising image modality in relation to PU (Akins et al. 2016; Swaine et al. 2018). The main objective of this PhD project is to evaluate the possible biases introduced by using 2D US-derived FE models in place of 3D MRI-derived FE models for the analysis of strain intensities and localizations in relation to personalized sacral PU risk assessment.
The PhD project is part of the H2020 European Training Network “Skin Tissue INTegrity under Shear” (H2020-MSCA-ITN-2018 STINTS). The aim of the STINTS project is to get a better understanding of complex biomechanical and biochemical factors responsible for the skin damage in reaction to prolonged pressure, shear forces, and friction. My PhD project focuses on the development of subject-specific FE models of buttock soft tissues to evaluate the intensities and localizations of strains when the body interacts with supporting surfaces.