title: Clinically relevant mechanical testing of hernia graft constructs.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA. Electronic address: sahoos@ccf.org.
authors.forename: Sambit
authors.initials: S
authors.lastname: Sahoo
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA; Department of Biomedical Engineering, University of Akron, Akron, OH 44325, USA.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: DeLozier
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Erdemir
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Derwin
mesh_terms: D059685:Herniorrhaphy; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D055595:Mechanical Phenomena; D013314:Stress, Mechanical; D019737:Transplants
keywords: Ball burst tests; Biomechanical properties; Construct testing; Hernia mesh; Planar biaxial tests; Ventral hernia repair