Finite element analysis of esophageal atresia repair with biodegradable polymer sleeves

Esophageal atresia, which occurs in 1 in every 4100 live births, is a potentially lethal congenital malformation resulting in discontinuity of the esophagus. Treatment requires approximating the disconnected esophageal segments and suturing the ends to restore continuity. Due to excessive anastomotic tension, leaks and strictures are prevalent in primary surgical repair of the esophagus especially in the subset of neonates presenting with long gap atresia (>3 cm between esophageal segments). Extracellular matrix derived scaffolds and biodegradable polymer scaffolds have been investigated in preclinical models for use in alleviating esophageal anastomotic tension with varying degrees of success. We have previously described the suitability of biodegradable shape memory materials for use in a number of soft tissue repair applications. Developing repair strategies addressing esophageal atresia requires a framework for approximating tension at the anastomosis. In this study, we describe a computational framework for approximating esophageal anastomotic tension to study the impact of primary and device supported repair. The esophagus was modeled as an idealized concentric cylinder comprised of mucosal and muscle layers described by nonlinear strain energy functions and a mixed fiber model with a Neo-Hookean base material (FEBIO studio). Sutures were modeled as nonlinear elastic springs carrying only tension, and shape memory polymers were modeled as nonlinear elastic materials using one term Ogden parameters. The impact of suture bite (length of suture from anastomosis), sleeve material properties, sleeve suture strategy, and gap length were evaluated with respect to anastomotic LaGrangian strain, displacement magnitude, and strain energy density. With increasing gap length, there was an increase in anastomotic strain, displacement magnitude and strain energy density. Increasing the suture bite length decreased strain at the anastomosis. Application of the sleeve reduced strain, displacement and strain energy to a greater extent in longer gap atresia. Increasing the number of sutures to apply the sleeve did not decrease the esophageal strain compared to sleeves with lesser number of sutures. Sleeve material testing revealed an interplay between the nonlinear mechanical properties of the selected materials and their contribution to reducing anastomotic tension. Taken together this study provides a unique framework for computational verification of design hypothesis broadly addressing clinical procedure optimization, material design, and device design for surgical repair of esophageal atresia.