A mattress contact model for a musculoskeletal simulation of human rolling

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Shotwell, Casey M.
Hakansson, Nils A.

Limited mobility affects a lot of people, including those who have recently had surgery or major trauma, the geriatric population, and people with disabilities. Many people with limited mobility cannot reposition themselves in bed, which can lead to pressure ulcers. Pressure ulcers are caused by unrelieved pressure and are difficult to treat. To prevent pressure ulcers, a patient must be repositioned every two hours. However, currently, there is no way to reposition a patient without significant injury risk to the caregiver. Healthcare providers experience a high frequency of lower back pain and injury caused by moving patients. The objective of this research was to create and validate a contact model that successfully characterizes the mechanical behavior of a mattress to be used in further studies related to human rolling. Currently, no model of human rolling involves contact with a mattress. Data were collected from drop tests and horizontal pull tests of a bowling ball on a memory foam mattress and MTS machine tests of a portion of a memory foam mattress in order to characterize the contact properties of the model. A model of a ball on a tilting mattress was created in an open-source musculoskeletal modeling program called OpenSim. A similar experimental test was conducted with a mattress and a bowling ball to test the validity of the computer model simulation. The simulation result was inconsistent with the real-life trials because the ball fell through the mattress. More work is needed to create a functioning model.

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Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Biomedical Engineering