Clinically relevant mechanical testing of hernia graft constructs.

Abstract

To understand the mechanical behavior of grafts in the context of hernia repair, there is a need to develop and adopt methods for mechanical testing of grafts in a clinically-relevant manner with clinically-relevant outcomes. Ball-burst and planar-biaxial methods were used to test three commercially-available hernia grafts (DermaMatrix, Biodesign, VitaMesh Blue). Both load-to-failure and cyclic fatigue tests were performed (n=6-11/group/test). Grafts were tested as sutured constructs in patch geometry. Dilatational strain analysis was performed considering the construct (both test methods) or the graft (planar-biaxial only) as the area of interest. DermaMatrix, Biodesign, and VitaMesh grafts showed differences in mechanical properties at the point of construct failure (load, in-plane load-per-suture and membrane tension) in ball-burst tests and differences in sub-failure properties (stiffness, dilatational strain at 16N/cm and cyclic mechanical properties) in planar-biaxial tests. In both load-to-failure and cyclic fatigue tests, each graft construct tended to be stiffer in planar-biaxial than ball-burst testing. In biaxial testing, the strain analysis method influenced the mechanical properties with the construct being more compliant than the graft. This study demonstrates that graft-fixation method, test mode and analysis method are important considerations for mechanical characterization of hernia grafts. Ball-burst tests can only estimate construct or material properties, whereas planar-biaxial tests capture anisotropy and can estimate construct, graft and material properties of the same test specimen. When the clinical performance of a graft in the context of hernia repair is of interest, testing a sutured construct and performing construct strain analysis arguably provides the most clinically-relevant assessment method.