Analysis of mechanical response of fistula plug for structure optimization

Anal fistula is one of the three greatest anorectal diseases with a high prevalence. The traditional treatments(e.g., surgery) for fistula have limitations due to damage to the internal anal sphincter of patients. With recent advances in biomaterials, treatments based on biomaterial filling (e.g., scleraprotein injection, fistula plug) have emerged as novel therapies for fistula. The anal fistula plug (e.g., based on small intestinal submucosa (SIS)) has attracted increasing attention because of short term healing rate and biocompatibility. However, challenges remain for this method such as plug falling as observed in clinics. To address this, this paper analyzes the case of SIS falling under physiological condition from mechanical point of view using ANSYS simulation. It then proposes three new geometrical structures for fistula plug and compares their mechanical behavior (e.g., axial stress, reaction of constraint) with that of clinically used structure (cone shape). Based on the simulation, it optimizes the geometric parameters of fistula plug. The approach developed here can help to improve the design of fistula plug for better clinical treatments.