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Mechanical Characteristics of a Polymer Spring Device used to Lengthen Small Intestine


Short Bowel Syndrome (SBS) is a condition that occurs due to an insufficient amount of small intestine needed for nutrient absorption and water regulation of the body. A compression spring device is being developed in order to provide a mechanical stimulus to the tissue, as this type of force has been shown to promote lengthening of the tissue. The research completed in this thesis investigated the mechanical characteristics of the spring device and attempted to relate it to the functionality in rat and porcine intestinal tissue.

Results from the evaluation of the springs show that Poly(å-caprolactone), or PCL, is a sufficient polymer to use for creating a biodegradable device as the spring dimensions can be adjusted through variations in the diameter, thickness, and band size in order to provide an adequate spring constant for multiple animal types. Design of the springs, however, need to take into account the size of the gelatin capsule used, the amount of plastic deformation and creep behavior of the spring under compression for an extended time period, and the variation in the mechanical properties of the animal soft tissue that requires lengthening.

Integration of the spring in-continuity requires a feature that will provide a mechanical resistance to force that is greater than the force of the spring in the compressed state. The spring still requires further development and any design should also take into account the possibility of intestinal perforations or obstructions. The polymer spring device provides a good means towards developing a treatment option for SBS, and other potential soft tissue lengthening needs of the body.

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