EP234 - Construction Of Three-dimensional Finite Element Model of Anorectum In Patients With Grade III Hemorrhoid Prolapse Based On Magnetic Resonance Imaging

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Purpose/Background: Using magnetic resonance data set and three-dimensional reconstruction technology to construct a three-dimensional finite element model of anorectum in patients with grade III hemorrhoid prolapse, and explore a new method and idea for the basic research of hemorrhoid disease.

Methods/Interventions: The mechanical parameters of the mucosal part removed from 30 patients with grade III hemorrhoid prolapse after haemorrhoidectomy obtained by mechanical measurement. Different modes of hemorrhoid ligation were simulated on the model, and the changes of stress and displacement at the ligation point corresponding to anal margin were observed under different defecation pressures.

Results/Outcomes: A three-dimensional finite element model of anorectum in patients with grade III hemorrhoid prolapse was successfully constructed. The elastic modulus of anorectal mucosa of 30 cases with pathological changes was obtained, and they were divided into six groups according to the numerical order, and the average elastic modulus of mucosa in each group was taken to get six models. For each model, single-point, double-point (vertical) and three-point (inverted triangle) ligation simulation of anal cushion mucosa was carried out. When the defecation pressure was 0mmHg, the displacement of the double-point ligation group was the largest, followed by the single-point ligation group, and the three-point ligation group was the smallest. The difference among the three groups was not statistically significant (P=0.77). With the increasing defecation pressure (20mmHg, 40mmHg), the displacement of the single point ligation group gradually increased, but there was still no statistical difference among the three groups (P=0.55, P=0.28). When the defecation pressure increased to 60mmHg and reached 200mmHg, the displacement of the single-point ligation group was significantly higher than that of the other two groups, and the difference among the three groups was statistically significant (P < 0.05). When the defecation pressure was 0mmHg, 20mmHg and 40mmHg, there was no statistical difference among the three groups (P > 0.05). When the defecation pressure continued to rise, from 60mmHg to 200mmHg, the stress value of the single point ligation group was significantly higher than that of the other two groups, and the difference was statistically significant (P ≤0.01).

Conclusion/Discussion: In the absence of defecation, all three ligation methods can improve hemorrhoid prolapse, but there is no difference in the improvement effect. The operation method of single-point ligation may be unstable due to high defecation pressure during postoperative defecation, which may cause the ligation point to loosen and thus affect the surgical effect. Two-point ligation and three-point ligation may bring more stable curative effect to patients. Using magnetic resonance three-dimensional reconstruction technology and finite element method to construct anorectal simulation model of patients with grade III hemorrhoid prolapse can carry out biomechanical research, provide theoretical basis for the formulation of clinical surgical strategy, and pave the way for expounding the pathological process of anal cushion downward from the biomechanical point of view in the future.