Date of Award

8-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Bioengineering

Committee Member

Dr. Karen J.L. Burg, Committee Chair

Committee Member

Dr. M. Scott Taylor

Committee Member

Dr. Frank Alexis

Committee Member

Dr. Kenneth Webb

Abstract

Hernia repair is one of the most frequently performed surgical operations, with the vast majority of these surgeries employing a “tension-free” repair technique with synthetic surgical meshes. Traditionally, meshes for hernia repair have been designed with high strength in order to produce a robust repair; unfortunately, current designs are unable to respond to the dynamic biological needs of the wound healing process. As a result, patients undergoing mesh hernioplasty often suffer from mesh contraction, reduced wound site compliance, fibrosis, and/or chronic pain. The aim of this dissertation was to design and assess a novel, selectively absorbable mesh system for soft tissue repair which exhibits initially interdependent load-bearing components that transition to independent in situ functional properties. More specifically, the mesh design was constructed to provide (1) a short-term stability phase to protect the developing tissue, (2) a mechanical load transitioning phase for support as the selected absorbable component begins to lose mechanical strength, and (3) a long-term compliant phase to allow mechanical sharing of loads between the deposited tissue and implanted construction. The designed mesh system was evaluated in a chronic ventral hernia model in rabbits and compared to the clinically relevant predicate, UltraPro™ mesh (a partially absorbable mesh currently marketed by Ethicon). Mechanical evaluation of the resulting mesh/tissue complex at 4, 8, and 12 weeks indicated that, while the designed mesh system resulted in a stiffer repair site initially (as compared to UltraPro™), the mesh transitioned into a significantly more compliant repair by 12 weeks. Furthermore, the mechanical contribution of the deposited collagen increased at each time point for UltraPro™, but decreased for the designed constructions. The UltraPro™ result suggests a possible cause for the increased long-term abdominal wall stiffness seen in mesh hernioplasty today (i.e. a cycle of constantly stiffening scar plate). Histopathological assessment indicated that the designed constructions triggered a statistically more intense foreign body response for the novel mesh constructions which allowed rapid integration into abdominal wall. This also led to a lower ratio of Type I/III collagen, although the results are limited due to the longest time point of 12 weeks, at which point the abdominal wall has not reached complete remodeling and maturity and all absorbable portions of the mesh are not completely absorbed.. Overall, the results of this study show the capacity of the developed constructions to modulate the tissue response of the healing abdominal wall based on temporal dynamic mesh mechanics. In addition, the novel meshes studied as part of this dissertation have the potential of reducing common complications associated with mesh hernioplasty, including mesh contraction, loss of tissue compliance, and reduction in severity of visceral adhesions. Collectively, these results provide justification for further development and assessment of multi-phasic meshes as those described within this body of work.

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