Finite Element Analysis for Evaluation of Pressure Ulcer on the Buttock: Development and Validation

Abstract

The interface pressure is currently the only clinical tool to estimate the risk of sitting-related pressure ulcers. However, it provides little information on the loading condition in deep tissues. We present a comprehensive 3-D finite element (FE) model for human buttocks with the consideration of the joint configuration and realistic boundary conditions in a sitting posture. Sitting induced soft tissue deformation, internal pressure, and von-Mises stress were computed. The FE model was well validated qualitatively using actual displacement obtained from magnetic resonance imaging (MRI) images. FE analysis demonstrated that the deformation induced by sitting pressure was substantially different among muscle, fat, and skin. The deformation of the muscle varied with location and the maximum was seen in the regions underneath the bony prominence of ischial tuberosity. In these regions, the range of compressive pressure was 65-80 kPa, 50-60 kPa, and 55-65 kPa, for skin, fat, and muscle, respectively. The von-Mises stress distribution had a similar pattern. In conclusion, this study suggests a new methodology for the development and validation of FE models for investigating the risk of sitting-related soft tissue

Evaluation of a new sitting concept designed for prevention of pressure ulcer on the buttock using finite element analysis

“…This phenomenon may be the consequence of the incompressibility of the soft tissue. In this model, we used a first order polynomial elastic Moony-Rivlin model [7] with Poisson ratio ≅ 0.485 [15] to represent the nearly incompressive characteristic of biological tissue. Therefore, when some locations, such as the area beneath the ischial tuberosity, endure large compressive deformation, the soft tissue may be pushed to the neighboring locations, which results in a slight local increase of the tissue thickness.…”

“…In this sense, the muscle fibers, which may generate an anisotropic characteristic of the material in tensile contraction, do not express much anisotropy in compression. In addition, the recognition of the muscle tone in our FE simulation [15] may also compensate part of this limitation.…”

“…In our previous study, a 3D FE model [15] was created based on the buttock-thigh structure reconstructed from MRI images obtained in a simulated sitting posture (Fig. 2a right).…”

“…using the Off-Loading posture, will have profound effect in reducing the mechanical stress within deep soft tissues. The objective of this investigation was, therefore, to evaluate the Off-Loading concept using a 3D FE model which has been developed and validated in our previous study [12,15]. It was expected that the FE analysis may help predict reliably how the skin, fat and muscle in the buttock-thigh region mechanically respond differently to the sitting load, as compared with a regular sitting posture.…”

A computational, tissue-realistic model of pressure ulcer formation in individuals with spinal cord injury

“…Whereas in the previous version of the model pressure was applied evenly across the entire field, in this version, it was applied maximally (value determined by the parameter, pressure-intensity) to a circular area in the center of the field and decreasing radially outward. This allowed representation of pressure over a bony prominence and the surrounding tissue, which also experiences pressure, but to a lessening degree [23,24]. Next, the PUABM code was altered so that neutrophils and macrophages enter the tissue in a resting state and can be activated by one of two circulating The ABM was built iteratively, incorporating domain knowledge and data from the literature, then validated with clinical data.…”