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ANZMOSS - ANZGOSA 2020 Virtual Conference
ANZMOSS – ANZGOSA 2020 Virtual Conference
ANZMOSS - ANZGOSA 2020 Virtual Conference
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Preferential transfer of shear forces to the proximal staple line in sleeve gastrectomy: A finite element analysis

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Description
BACKGROUND AND AIM 
Staple-line leaks occur predominately adjacent to the OG junction. A high-pressure system is proposed to be implicated in chronic leaks, however, objective data to support this is limited. We aimed to characterise how intraluminal pressurisations and gastric geometry transfer stress to the luminal wall.
 
METHODOLOGY
i) High resolution manometry was used to compare sleeve gastrectomy patients to obese controls.
ii) Finite-element analysis (FEA) simulated gastric pressurisation with oesophageal shortening. Geometry was based on volumetric CT of a sleeve shaped with a 34Ch bougie.
 
RESULTS
Demographics: age 40.5+/-17.7years vs. 42.5+/-15.7(p=0.22), 90% female
vs.78.5%(p=0.615), weight 122.3+/-21.0kg vs. 110.6+/-118.9(p=0.771), BMI 48+/-11.7kg/m2
vs. 38.3+/-3.8(p=0.023). Peak swallow intragastric isobaric pressures were raised post sleeve 13.49+/-1.34 vs. 31.58+/-
2.1mmHg(p=0.0002). The intragastric/mid-oesophageal (IG/MO) pressure ratio was more negative in the sleeve gastrectomy cohort -1.17+/-1.4 vs.-4.36=/-7.4mmHg (p=0.01). During the basal phase peak end-expiratory pressure 3.28±3.4 vs. 5.78±6.5mmHg (p=0.236) and IG/MO ratio -0.123±0.8 vs. -1.0±1.8mmHg (p=0.081) was similar.
 
Six models underwent FEA. volume 242.3ml (208.5-351). 80% of models had maximal wall stress at the GOJ. High stress was clustered at the GOJ and irregular contours in the greater curvature. Smooth contours did not show concentrated deformation or material failure. The leak model demonstrated significant pressures at the incisura rather than the GOJ. The highest stress geometry at the GOJ was the dog ear model 218.3kPa. Variation in dog ear size led to higher stress at the GOJ. 
 
CONCLUSIONS
Significant high-pressure episodes occur in the sleeve during oesophageal contractions. Simulations suggest that maximal strain is transmitted to the proximal stomach. Variation in the geometry of the greater curvature influences the distribution of luminal wall stress. This may be a key factor in the initiation and perpetuation of sleeve leaks and potential therapeutic target.
Authors
Paul Burton - , Wendy Brown - Monash University, Sam Liao - Alfred Health, William Catchlove - Alfred Health, and Gillian Lim - Monash University
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