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Lesch et al. Mini-invasive Surg 2023;7:20 https://dx.doi.org/10.20517/2574-1225.2023.24 Page 3 of 8

Figure 1. (A) Photo of the bench test and its elements (1: water cylinder with cover plate, 2: tank opening where pressure impacts are
applied to the mounted tissue, 3: base frame with pipe system including inlet and outlet valves and pressure tank); (B) Mounted
sutured tissue on the bench test during maximum pressure impact, suture tension is measured.

tissue types differ in their distinct median elasticity . The model tissues were repeatedly loaded with cyclic
[16]
impacts on our validated bench test, as previously described [13,16] . The test bench simulates high pressure
impacts on the sutured tissue with a customizable pressure plateau phase and maximum pressure, as it can
occur during heavy coughing. One out of three of our patients coughs over 400 times in the first 24 hours
postoperatively . Accordingly, we loaded the reconstructed tissues 425 times with cyclic pressure impacts.
[17]
The bench test is shown in Figure 1.

We investigated the performance and stability of various suture techniques for midline abdominal incisions.
We chose two different types of defects. For defect type one, we cut a 15 cm long medial incision into the
tissues. For defect type two, we punched an additional 5 cm large circular defect in the center of the
incision. The incisions were solely sutured in large-bite (0.8-1.2 cm bites) or small-bite (0.5-0.8 cm bites)
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technique with Monomax or PDS sutures USP 2-0 or USP 1. Monomax® suture material is manufactured
of poly-4-hydroxybutyrate. It differs from PDS in its ultra-long resorption time of 18 months and elasticity
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of 90%. The SWL ratio had to exceed 4:1 [10,18] . The incisions with defects were closed in a standardized
technique by two surgeons experienced in suture technique research. The nomination terminology is
[13]
given in Table 1. The exact test setup for each test is shown in Table 2.
The test was terminated if the reconstruction failed or if 425 DIS impacts were delivered. Failure was
defined as slackening of the suture, tearing of the suture through the tissue, or tearing of the tissue itself.
The occurrence and onset of the failure pattern were observed in the experiments. The study comprises a
total of 15 experimental series (ES), each involving ten experiments [Table 2].

Statistical analysis
For the groups with skewed results, the Kruskal-Wallis test was used for non-parametric testing. The
significance was analyzed with a Mann-Whitney U test. We used curves similar to survival curves that
illustrate the likelihood of a durable closure.

RESULTS
In eight ES (1-8), we performed a structured investigation of four influencing factors on the suture
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durability. We varied the stitch spacing (Large-Bite vs. Small-Bite), the suture material (Monomax vs. PDS)
and the suture thickness (USP 1 vs. 2/0), and the tissue type (bovine and porcine). The WSL showed no
significant variation with values between 4.3 to 4.4 throughout ES 1-8 [Table 2]. In series 9-15, we