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Page 2 of 8 Nessel et al. Mini-invasive Surg 2023;7:21 https://dx.doi.org/10.20517/2574-1225.2023.21

incisional hernia repair should take into account the biomechanical aspects involved.

Keywords: Hernia, incisional hernia, biomechanics, GRIP, biomechanically calculateed hernia repair, durable hernia
repair, durable incisional hernia repair

INTRODUCTION
The recurrence rate of incisional hernia repair is 25% five years after mesh-based incisional hernia repair .
[1]
This rate has remained relatively constant over the decades, disregarding open, laparo-endoscopic, or
robotic approaches . A biomechanical concept gave excellent results in incisional hernia repair after one
[1]
year . The concept is based on the analysis of cyclic loads mimicking coughs or Valsalva maneuvers.
[2,3]
Dynamic intermittent strain (DIS) is repeatedly delivered to assess compounds made from tissue, hernia
mesh, and fixation materials. The analysis includes a self-built bench test and results in coefficients
characterizing the adhesiveness of each component . The results are summed in a critical (CRIP) and a
[4,5]
gained resistance towards impacts related to pressure (GRIP).

So far, about 10% of commercially available hernia meshes, sutures, tacks, and adhesives are
biomechanically characterized with pulse loads for clinical purposes . The design of a future
[6,7]
investigational strategy has to take into account a basic principle of pulse load testing for incisional hernia
repair: the retention forces of the components are not simply additive but rather depend on factors such as
the energy uptake of the tissues in their different lamina, the cut-out and fiber orientation, the specific
configuration of various materials, and the impact area . In order to concentrate on relevant topics, it is
[8,9]
essential to define specific research questions. The potential for future advancements in this field includes
areas such as policy making and regulatory and clinical approaches.

Historical perspective
In the field of material sciences, the durability of compounds is influenced by factors such as cyclic load,
boundary conditions, interface influences, notch effects, stress concentration, and their regional
distribution. Research investigating these influences has been ongoing since 1855 [10,11] . Standardization of
cyclic load testing for fatigue strength has been increasingly implemented since the establishment of DIN
50100 in 1951 . In 1958, trauma surgeons adopted this approach with a focus on biomechanics and cyclic
[12]
load testing . Despite a success story in bone and ligament surgery, testing is not yet fully standardized as
[13]
compared to solid materials. The most recent version, DIN 50100.2022-12, describes load-controlled fatigue
testing for metallic specimens and components. The first steps for polymeric and biological materials have
recently started with an effort to adapt ASTM standards to musculoskeletal soft tissue . Current research
[14]
focuses on a standardized test specimen, the test coupon. In the realm of soft tissue surgery, a biomechanical
“fail-safe” approach is just beginning to emerge. However, there is still no consensus regarding the
standardization of the test coupon or of the boundary conditions.

Ten years ago, our groups of surgeons and basic scientists started cyclic loading as a test in order to improve
the results of incisional hernia repair. A biomechanical approach was chosen. Applying cyclic pulse loads on
a bench test (DIS), mesh materials were tested and classified, simulating coughing actions . Using
[6]
computed tomography of the abdomen at rest and during the Valsalva maneuver, the tissue elasticity of
[2]
individual patients was assessed when necessary . The CRIP and GRIP of the mesh-tissue interface were
calculated . The C/GRIP formula incorporates various aspects of the surgical techniques, such as suturing
[2-9]
with a small-stitch-small-bite technique, tackers, or adhesive for enhanced bonding [Figure 1]. Here, we
present research questions influential to durable incisional hernia closure. In our belief, a durable repair of
the abdominal wall can be defined as GRIP > CRIP. Which boundary conditions derived from cyclic load