The Resistance to Traction Forces Differs Substantially Between Intestinal Parts, but Not Between In- and Outbred Strains of Mice

Background/Objectives: Anastomoses under tension are associated with anastomotic leaks and strictures. In experimental surgery, anastomoses are frequently tested for their resistance to traction forces, but without the surgically untouched organ as a comparator. We therefore investigated whether and to what extent the breaking forces along the gastrointestinal tract differed in the intact intestinal organs to provide some data for the comparison of anastomoses to it and guide sample size estimation in the mouse. Methods: We included 54 mice of the Crl:CD1(ICR) stock and, as a comparator, 10 mice of the C57Bl/6J and 10 mice of the C57Bl/6NCrl strain of both sexes. We determined breaking forces using a motorised test stand. Results were compared via estimated marginal means with a control of the false-discovery rate by the Benjamini–Hochberg procedure. Results: In all mice strains, the resistance to traction forces was in a descending manner: stomach (mean (µ) ≥ 1.87 Newtons, standard deviation (σ) ≤ 0.63) > rectum(µ > 1.31 Newtons, σ ≤ 0.63) > caecum (µ > 1.1 Newtons, σ ≤ 0.37) > colon(µ > 0.93 Newtons, σ ≤ 0.31) > duodenum (µ > 0.65 Newtons, σ ≤ 0.28) > jejunum (µ > 0.5 N, σ ≤ 0.16) > ileum (µ ≥ 0.43 Newtons, σ ≤ 0.13). The analysis of variance showed a statistically significant effect of the mouse strain on breaking forces (F(2,497) = 16.81, p < 0.001). This was also the case for the investigated organ (F(6,497) = 104.18, p < 0.001) and the interaction between strain and organ (F(12,497) = 2, p = 0.022), indicating a difference between strains. Only the stomachs differed between the included strains; the stomach of Crl:CD1(ICR) sustained −0.81 Newtons (t = −6.23, p < 0.001) compared to those of C57Bl/6J, and −0.37 Newtons (t = −2.88, p = 0.006) compared to those of C57Bl/6NCrl. Other statistically significant differences were absent. Conclusions: Differences in breaking forces between inbred strains and outbred stock were only present for the stomach. Our results may provide a first baseline of breaking force measurements for other studies investigating anastomoses and the respective sample size analyses.