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Nessel et al. Mini-invasive Surg 2023;7:21 https://dx.doi.org/10.20517/2574-1225.2023.21 Page 3 of 8

Figure 1. This is a figure representing the GRIP concept. Forces acting on the abdominal wall are considered as linked chains. Failure
mainly occurs at the mesh-tissue interface. Cyclic load is delivered on a bench test and can assess the influence of the different forces.
A load limit CRIP must be surpassed for a durable reconstruction. A shakedown process as a prerequisite for healing requires a
sufficient GRIP of the reconstruction CRIP: critical resistance to impacts related to pressure; GRIP: gained resistance to impacts related
to pressure.

testing in material sciences can be investigated and applied to the clinical situation in the future? What are
the consequences for policy making and regulatory and clinical approaches?

STATE OF ART
Is cyclic load relevant for abdominal wall reconstruction?
Most daily activities imply cyclic load to the abdominal wall . This is evident from the increase in
[15]
intraabdominal pressure during these activities. Notably, water immersion decreases intraabdominal
[16]
pressure and reduces pulse load to the abdominal wall . However, increasing effort elevates
intraabdominal pressure even during water immersion. During straining and vomiting, high values
exceeding 250 mmHg are measured . Intraabdominal pressure values above 120 mmHg start to destroy an
[17]
abdominal wall reconstruction after 325 repetitions . Such loads are easily reached hundreds of times every
[18]
day in human life.

What kind of cyclic load needs to be studied?
The load spectrum starts with sharp peaks lasting only a few milliseconds, such as those experienced during
coughing. Additionally, the spectrum includes increasing pressure levels over seconds once the glottis is
closed, as seen during the Valsalva maneuver [19-22] . Both forms of load can be delivered with the cyclic load
test stand available to date for incisional hernia repair. So far, plateau phases up to 400 msec have been
investigated . These plateau lengths are already reached after 30% of an isometric maximal lifting effort
[2,5]
[23]
with longer plateaus at higher efforts .
Under which circumstances is a bench test load relevant to human daily life?
Both pulse and plateau loads were observed during walking, jumping, climbing stairs, vomiting, or straining
for bowel motions. Among these activities, the highest intraabdominal pressures, usually above 200 mmHg,
were found during squats [17,24] . In daily life, pressure levels reach these values at about 10% of the values per
hour . Within one hour, 76% of all measured values reach 100 mmHg, while an additional 13% exhibit
[15]
peak values up to 200 mmHg. It is important to note that these data were derived from a few healthy
volunteers, and large-scale measurements in patients are currently unavailable. By counting coughs in
patients and assuming intraabdominal pressure peaks as previously reported, a load case of 400 and more
peaks above 200 mmHg was taken as a critical load in one-third of our patients [4,20] . During prehabilitation,
intraabdominal pressure peaks could be evaluated for individual patients suffering from incisional hernias.
It should be noted that individuals with better physical fitness tend to have lower intraabdominal pressures