Characterising the mechanism of cell failure due to shear using a combined numerical and analytical approach

The treatment of tissue damage caused by pressure ulcers (also known as bed sores) and urinary tract infections costs the global medical industry more than £100 million every day. This research investigates the hypothesis that terminal tissue damage is caused by excessive shear stress rather than normal contact pressure. Therefore, this study considers the effect of normal and shear stress components on cell health through a combined experimental, analytical, and numerical modelling approach. Finite Element Analysis has been employed to understand the effect of normal and shear (tangential) forces on a cell structure with a 100-micrometre diameter. The structure of the cell was represented by the six major cell components: membrane, actin cortex, cytoplasm, microtubules, intermediate filaments, and nucleus. The initial model predictions show that the cell membrane and actin cortex are penetrated by the microtubules at a cell deformation of 16 micrometres. A Von Mises analytical approach was used to determine the yield stress at cell death. The study concludes that the application of shear force during compression increases the rate of cell death.