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Page 10 of 13 Lesch et al. Mini-invasive Surg 2023;7:25 https://dx.doi.org/10.20517/2574-1225.2023.31

In addition, force absorption and distribution by the abdominal wall could be supported by an abdominal
[31]
binder. Whether a simple abdominal binder provides a significant benefit is currently undetermined .
The concept of cyclic load over time is vitally important but often underappreciated by hernia surgeons.
Surgeons must be aware of the biomechanical conditions within the abdomen, highlighting the need for
continuous education and research. Biomechanical considerations form part of the hernia base camp
[32]
endorsed by the European Hernia Society .

Plastic shakedown as a requirement for healing - options for the behavior of reconstructed tissue
Figure 8 illustrates the biomechanical behavior patterns of reconstructed tissues under cyclic loading. Before
the start of the experiment, no deformation is visible [Figure 8A]. The compound deforms within the first
few cycles [Figure 8B]. Two scenarios can develop from this point. Firstly, the first cycles exceed the yield
limit through the total amount of subliminal impacts. The compound is not able to withstand the cyclic
load. It deforms in each individual cycle [Figure 8C]. Deformation can be visible as elongation or
slackening, which forms an intermediate state and can progress to complete failure, a hernia. Secondly, after
a certain number of load cycles, the deformation changes from plastic to elastic behavior [Figure 8D]. The
original state is no longer restored, but failure does not occur either. This is called a plastic shakedown. If
the cycles are below the failure limit within the loading period allowing a steady state, the compound bears
the load successfully [33,34] .

The goal of abdominal wall closures is to achieve a “strain stable condition” without failure of the
reconstruction. The strain-stable condition is considered to be achieved when the compound has survived
425 impacts. If 425 impacts are not achieved, failure of the compound occurs in a smooth transition. Suture
failure mostly begins early after surgery [9,27] , such as major tissue deformation [Figure 6]. A resulting fascial
[35]
dehiscence that can lead to the tearing of the suture line is mostly invisible [11,12] . Herniation usually follows
fascial dehiscence that expands to more than 11 mm in four weeks .
[36]
During the first 100 impacts, the highest rate of failures occurs. This matches our finding that the major
plastic deformation takes place during the first impacts [Figure 6]. When using a cover plate with a larger
opening, greater elongation and deformation of the tissue are visible. This is accompanied by significantly
higher failure rates. Both findings show the same result. The greater the deformation of the tissue appears,
the higher the likelihood of failure. If the compound is unable to establish a strain-stable condition called
plastic shakedown, failure occurs.

In conclusion, realistic repetitive cyclic loading is required for us to assess the abdominal wall properties
and the durability of a reconstruction. A lifelike evaluation of the reconstruction durability can only be
provided by our bench test protocol. Pulse loads transmit energy to the abdominal wall repeatedly. The
amount of energy is related to the peak pressure, the impact area, and the duration of the cyclic pulse. The
higher the applied peak pressure, the more energy is transferred to the mesh-tissue compound, leading to
more failures. In most cases, increasing the peak pressure by 30 mmHg lowers the durability by 20 %. The
elongation of the plateau phase led to a significant decrease of the durability. Simulating a worst-case
scenario with 1000 DIS impacts, about 10 % more failures occur beyond the 425th DIS impact. However,
after the 500th impact up to the 1000th impact, the durability remains stable.

During the first 100 DIS impacts, the major part of the tissue deformation takes place. Also, a major number
of failures occurs during that period. Using a cover plate with a larger opening leads to greater tissue
deformation. This results in significantly higher failure rates. The greater the deformation of the tissue