Experimental models of high-risk bowel anastomosis in rats:A systematic review

BACKGROUND Anastomotic leaks remain one of the most dreaded complications in gastrointestinal surgery causing significant morbidity,that negatively affect the patients’quality of life.Experimental studies play an important role in understanding the pathophysiological background of anastomotic healing and there are still many fields that require further investigation.Knowledge drawn from these studies can lead to interventions or techniques that can reduce the risk of anastomotic leak in patients with high-risk features.Despite the advances in experimental protocols and techniques,designing a high-quality study is still challenging for the investigators as there is a plethora of different models used.AIM To review current state of the art for experimental protocols in high-risk anastomosis in rats.METHODS This systematic review was performed according to The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.To identify eligible studies,a comprehensive literature search was performed in the electronic databases PubMed(MEDLINE)and Scopus,covering the period from conception until 18 October 2023.RESULTS From our search strategy 102 studies were included and were categorized based on the mechanism used to create a high-risk anastomosis.Methods of assessing anastomotic healing were extracted and were individually appraised.CONCLUSION Anastomotic healing studies have evolved over the last decades,but the findings are yet to be translated into human studies.There is a need for high-quality,well-designed studies that will help to the better understanding of the pathophysiology of anastomotic healing and the effects of various interventions.

Strength differential effect and influence of strength criterion on burst pressure of thin-walled pipelines

In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC- based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.

ESTIMATE OF BURSTING PRESSURE OF MILD STEEL PRESSURE VESSEL AND PRESENTATION OF BURSTING FORMULA

In order to get more precise bursting pressure formula of mild steel, hundreds of bursting experiments of mild steel pressure vessels such as Q235（Gr.D） and 20R（1020） are done. Based on statistical data of bursting pressure and modification of Faupel formula, a more precise modified formula is given out according to the experimental data. It is proved to be more accurate after examining other bursting pressure value presented in many references. This bursting formula is very accurate in these experiments using pressure vessels with different diameter and shell thickness. Obviously, this modified bursting formula can be used in mild steel pressure vessels with different diameter and thickness of shell.

Prediction of Burst Pressure of a Radial Truck Tire Using Finite Element Analysis

This paper is concerned with the numerical prediction of the burst pressure of a radial truck tire. Even though relatively rare, the tire fracture or failure brings up a big accident. Especially, the tire burst or rupture is a rapid loss of inflation pressure of a truck and bus tire leading to an explosion. The tire burst pressure, under this extreme loading condition, can be predicted by identifying the pressure at which the cord breaking force of the composite materials is attained. Recently, the use of finite element analysis in tire optimal design has become widely popular. In order to determine the burst pressure of a radial truck tire, an axisymmetric finite element model has been developed using a commercial finite element code with rebar element. The numerical result shows that the bead wire among the various layers modeled the rebar element breaks off first in the radial truck tire. The finite element modeling with the rebar element on the bead wire of a radial truck tire is able to well predict the tire burst pressure identifying the pressure at which the breaking force of steel bead wires is reached. The model predictions of tire burst pressure should be correlated with test data, in which case the tire is hydro-tested to destruction. The effect of the design change with the different bead structure on the tire burst pressure is discussed.

Theoretical Assessment of Burst Failure of Internally Pressurized Defect-Free Pipelines with Plastic Anisotropy

In the framework of finite deformation theory, the burst failure analysis of end-opened defect-free pipes with plastic anisotropy under internal pressure is carried out. The analytical solutions of burst pressure and the corresponding equivalent stress and strain are obtained for thin-walled pipes, which can take into account the effects of material plastic anisotropy and strain hardening exponent. The influences of plastic anisotropy on the burst pressure and the corresponding equivalent stress and strain are discussed. It is shown that the burst pressure and the corresponding equivalent stress and strain are dependent upon the plastic anisotropy of material, and the degree of dependence is related to the strain hardening exponent of material. In addition, the effects of the strain hardening exponent on burst failure are investigated.

Standards and methods for dent assessment and failure prediction of pipelines:A critical review

Dent,a common mechanical damage on pipelines,is associated with a significant local plastic deformation.Dents can cause pipeline failures,especially when they are combined with other types of defects such as gouges,fatigue,corrosion,and cracks.In this work,a systematic review of various assessment methods and standards for pipeline dents,including the combination of a dent with other defects,is conducted.Generally,the methods available today are not sufficiently accurate and reliable to assess pipeline dents,especially the dent-defect combinations.For plain dents on pipelines,both the depthbased criterion and the strain-based criterion are commonly used in engineering.Their main problems include inaccuracy and conservatism.For a dent combined with other defects,the existing assessment techniques are not mature enough to give reliable results.Both experimental testing and numerical modeling through finite element(FE)analysis are capable of investigating the influence of dents and dent-defect combinations on burst failure pressure of the pipelines,although an approximation to the reality is still the main difficulty existing in the experimental testing and FE analysis.Nowadays,relevant studies on assessment techniques for plain dents,a dent with fatigue and a dent with a single gouge have been common in literature.The combinations of a dent with corrosion or cracks have been rarely assessed due to complicated mechanisms involving a multi-physics coupling effect.Development of novel assessment methods by integrating mechanical stress and strain,electrochemical reactions and steel metallurgy will be a key topic to accurately assess the dent-defect combinations for improved pipeline integrity.

A biodegradable magnesium surgical staple for colonic anastomosis: In vitro and in vivo evaluation

Staplers have been widely used in the clinical treatment of gastrointestinal reconstruction.However,the current titanium(Ti)staple will remain in the human body permanently,resulting in some adverse effects.In this study,we developed a type of biodegradable staple for colonic anastomosis using 0.3 mm diameter magnesium(Mg)alloy wires.The wire surface was modified by micro-arc oxidation treatment(MAO)and then coated with poly-L-lactic acid(PLLA)to achieve a moderate degradation rate matching the tissue healing process.The results of tensile tests on isolated porcine colon tissue anastomosed by Mg and Ti staples showed that the anastomotic property of Mg staples was almost equal to that of Ti staples.The in vitro degradation tests indicated the dual-layer coating effectively enhanced the corrosion resistance and maintained the tensile force of the coated staple stable after 14-day immersion in the simulated colonic fluid(SCF).Furthermore,24 beagle dogs were employed to conduct a comparison experiment using Mg-based and clinical Ti staples for 90-day implantation by ent-to-side anastomosis of the colon.The integrated structure of Mg-based staples was observed after 7 days and completely degraded after 90 days.All animals did not have anastomotic leakage and stenosis,and 12 dogs with Mg-based staples fully recovered after 90 days without differences in visceral ion levels and other side effects.The favorable performance makes this Mg-based anastomotic staple an ideal candidate for colon reconstruction.

Experimental research of stent anastomosis of gastrojejunostomy in a porcine model

Background Gastrojejunostomy is one of the most frequently used procedures for general surgeons. The creation of anastomosis between various parts of the gastrointestinal tract is a basic technical component and major task in the daily practice of almost all gastrointestinal procedures. This research evaluated a new procedure of making gastrointestinal anastomosis with stent.Methods Twenty experimental mini-pigs were randomized into two groups. In stent anastomosis group （SA）, the anastomoses were constructed with a poly-levolactic acid stent. In hand-sewn group （HA）, the anastomoses were performed with a single-layer continuous suture. Abdominal X-ray with intraluminal contrast was performed on the 10th postoperative day. Five pigs of each group were sacrificed on the postoperative days 3 and 14 to determine anastomotic bursting pressure in situ, hydroxyproline concentration, and histopathological evaluation of the anastomotic sites.Results There was no intraoperative morbidity or mortality. The median time needed for the sutured anastomosis was （21.7±2.3） minutes and for the stent anastomosis was （11.9±1.9） minutes （P 〈0.001）. Abdominal X-ray with intraluminal contrast demonstrated normal gas distribution and showed no evidence of leakage or obstruction. Macroscopic appearance at the longitudinal opening of anastomosis was always good in both groups. The median anastomotic bursting pressure was （18.2±1.6） kPa in SA group on postoperative day 3, compared with （11.7±3.2） kPa in HA group （P=0.003）. The anastomotic bursting pressure on day 14 was not significantly different between SA group （（27.1±2.6）kPa） and HA group （（28.3±1.7） kPa） （P=0.388）. The hydroxyproline concentrations were not significantly different.Conclusions The stent anastomosis was not considered to be more difficult than a sutured anastomosis. This method is proved to be safe and feasible compared with the traditional hand-sewn method in the porcine model. The method increases early anastomotic strength in this study.