Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Bioengineering

Committee Member

Dr. Melinda Harman, Committee Chair

Committee Member

Dr. Donna Weinbrenner

Committee Member

Dr. William Richardson

Abstract

Polymeric surgical mesh is an implantable biomaterial used to treat muscular defects associated with abdominal hernias. Surgical meshes generally exhibit anisotropic material properties, but their in situ mechanical behavior is poorly understood when exposed to mechanical loading of the abdominal wall. Moreover, the mechanical influence of different types of peripheral fixation (e.g. sutures, tacks) used to attach the mesh is not well-characterized. Injury models of biomaterials implanted in load-bearing tissues (e.g. tendon, muscle) demonstrate that mechanical tension can signal optimal repair of fascial tissues or cause fibrous encapsulation. Therefore, it may be possible to link features of connective tissue deposition to loading conditions across surgical mesh. The broad objective of this thesis was to explore the influence of physiological mechanical loads on connective tissue formation surrounding the periphery of hernia mesh where fixation devices are commonly present. This objective was addressed through a comprehensive literature review of the biocompatibility of surgical mesh combined with an experimental design utilizing micro computed tomography (microCT) to guide histological analysis of in vivo hernia mesh explants. Presuming that peripheral fixation points (locations near sutures or tacks) on in situ hernia mesh experience high tension during physiological loading, it was hypothesized that histological features would be different at the peripheral rim compared to more centralized locations on the same explanted mesh. This thesis utilized the MeshWatch registry of hernia mesh explanted after in vivo function and microCT imaging to guide histological sectioning. Quantitative histological analysis pointed to a uniform inflammatory response consistent across both mesh types (heavyweight and lightweight) and locations (central and peripheral rim near fixation points). Overall, the ratio of mature to immature collagen was lower in the peripheral rim compared to more centralized locations on the same explanted mesh, consistent with the significantly higher amounts of immature collagen in the peripheral rim adjacent to mesh fixation points. These altered tissue responses near peripheral fixation points support studies linking cyclic strain and non-uniform loading conditions to variations in connective tissue deposition.

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