Development of a predictive and patient-dependent numerical model to prevent recurrence after incisional hernia repair (REPAIR)

Short accessible summary of the project :
The project focuses on the prediction and reduction of incisional hernia recurrence after laparotomy
surgery. The aim of the project is to develop a predictive finite element numerical model for the risk
development of abdominal hernia. A multi-scale anisotropic and patient dependent model will be
developed, accounting for the different layers of biological tissue between the skin and the internal
organs to optimize the surgery procedure and reduce incisional hernia recurrence.

1. Context:
The abdominal wall has several roles: i) it acts as a mechanical barrier to protect the internal organs,
ii) it supports the intra-abdominal pressures (IAPs) that develop in the abdominal cavity, and iii) it
ensures/eases trunk mobility during breathing and movement. Incisional hernias represent a break in
the continuity of the abdominal wall, altering the mechanical function of this composite tissue
composed of the following layers from surface to depth: skin, subcutaneous fat, anterior rectus fascia,
rectus muscle, posterior rectus fascia, preperitoneal fat and peritoneum [1]. From lateral side to the
midline, the muscular layer is composed of the external oblique, internal oblique and transverse
abdominal muscles. Several collagenous connective tissues (such as aponeuroses, or the linea alba)
integrate the different layers to form a functional composite structure [1]. When considering the pathogenesis of incisional hernias from a biological point of view, they are most often due to technical failures in anatomical repair, leading to wall fragility [2]. The treatment of these incisional hernias consists in reconstructing a normal anatomy and consolidating the wall with a prosthetic polymer mesh. This mesh can be placed preaponeurotic (subcutaneous), retromuscular or intraperitoneal, in contact with the viscera.

2. Objectives
The abdominal cavity could be represented as a pressurized reservoir. The wall of this reservoir is
multilayered with anisotropic mechanical properties between fascia, subcutaneous fat, muscle and
skin tissue. The main goals of the study are threefold :
a) Propose a predictive finite element numerical model that accounts for specific anisotropic material
properties and being patient dependent. This is currently nonexistent as numerical model are based
on homogeneous tissues and simplified geometries.
b) From the patient dependent model, study the stress concentration at the prosthesis fixation and
extract the specific characteristics (boundary conditions, threshold limits) leading to rupture and
hernia development.
c) Propose an optimization of the surgery procedure and prosthesis fixation to reduce significantly the
hernia occurrence risk.
To address this clinical problem, the PhD work will develop around the following two points :
a) Create a multi-layer predictive numerical model with hyperelastic anisotropic constitutive laws for
each of the layers, which are also geometry patient dependent. Indeed, the abdominal wall is a
composite structure, and very few studies have examined the mechanics of the different layers of the
human abdomen [3,4]. The anisotropic constitutive laws will be identified based on human
experimental data that are currently being extracted from a supported ITI transdisciplinary project by
B. Romain and D. George. The specific constitutive laws of the tissues composing the abdomen will be
available from Autumn 2025 to be integrated in the developed FE model during the PhD. The risk of
this step is moderate as some experimental data are available on pigs (can be partly interpreted) and
materials anisotropy are also partly available in the literature. A combination of both with more data,
specifically on human samples, is therefore necessary to optimize the modeling process and obtain
better results predictions.
b) After 3D FE model construction based on patient imaging data obtained from HUS Strasbourg, we
will run analyses for different prosthesis location and fixation based on surgical procedure load
conditions. Here, we aim to find the best position for the prosthetic mesh: subcutaneous
preaponeurotic? retromuscular? intraperitoneal? This objective of optimized placement of a
prosthetic mesh reduces the clinical risk of recurrence of ventral hernia after incisional hernia repair
[5]. The best localization of this prosthesis at the level of the abdominal wall layers has not been
formally demonstrated clinically.

6. medical need targeted by the project
Incisional Hernias (IH) are a frequent complication after abdominal surgery, with an incidence of 5–
25% after a laparotomy in the general population [1]. The recurrence rate after incisional hernia repair
is as high as 28% at 2 years after incisional hernia repair [2]. That’s why the appearance of an incisional
hernia or a recurrence after IH repair costs several million euros each year in terms of public health. A
5% reduction in the incidence of incisional hernias would result in savings over 4 million euros [3]. A
better understanding of the biomechanics of the abdominal wall would help reduce the risk factors for
incisional hernia occurrence and improve repair techniques to reduce the risk of recurrence. This will
also enable us to improve or propose prosthetic materials for the repair of these incisional hernias,
with the possibility of developing industrial patents. These improvements will help to improve patients'
quality of life, reduce postoperative pain and decrease the cost of managing this common pathology

Le laboratoire des sciences de l'ingénieur, de l'informatique et de l'imagerie (UMR7357)

L'année 2013 voit la naissance du laboratoire ICube, un formidable projet sous l'égide du CNRS, de l'Université de Strasbourg, de l’ENGEES et de l’INSA de Strasbourg. 

Le laboratoire rassemble à parts égales deux communautés scientifiques à l’interface entre le monde numérique et le monde physique, lui donnant ainsi une configuration unique.

Avec près de 650 membres, il est une force de recherche majeure du site de Strasbourg. Fédéré par l'imagerie, ICube a comme champs d'application privilégiés l'ingénierie pour la santé, l'environnement et le développement durable.

Mécanique, numérique, biomécanique