4. Surgical Research

Background:Understanding biomechanical properties of intestinal tissue is essential for advancing knowledge in gastrointestinal anastomotic healing.Tensile strength testing is one of the most standardized and reliable approaches for ex vivo evaluation.However, fresh intestinal tissue is not always available and the use of fixation techniques may alter the biomechanical characteristics of the samples and affect the validity of test results.This study aims to investigate and compare the biomechanical impact of commonly used preservation techniques on porcine small intestine with that of fresh tissue. Material and methods:A Zwick/Roell tensile testing machine was used to apply longitudinal force to porcine intestinal segments.Two synchronized cameras documented the tearing process from different angles.We evaluated stressstrain behaviour, stiffness, and maximum breaking strength across three preservation methods: frozenthawed, ethanol (35%), and formalin-fixed.Fresh intestine was incubated in PBS for same-day testing, served as the control.Each preservation method was assessed after 7 and 14 days.In total, 70 segments (n=10 per group) were analysed.Stress-strain curves were generated, and mechanical parameters were computed using a custom MATLAB algorithm. Results:Significant differences in stiffness were observed compared to fresh tissue for frozen-thawed (p = 0.0238) and formalin-fixed (p = 0.0036) samples, while ethanol-preserved tissue showed no significant change (p = 0.2348).Duration of storage also affected outcomes: stiffness differed significantly after 14 days for frozen-thawed tissue (p = 0.0248) and already after 7 days for formalin-fixed samples (p = 0.0024). Conclusion:Both preservation technique and storage duration substantially influence the biomechanical properties of porcine intestine.These findings are crucial when designing reliable and reproducible ex vivo models in surgical research.Moreover, they highlight the broader importance of accounting for preservation-related changes in biomechanical studies involving any biological tissue.Further investigations should explore ways to reduce such alterations and enhance the comparability of preserved and fresh specimens.