Franck Boutault

Comparison of linear and non-linear soft tissue models with post-operative CT scan in maxillofacial surgery

A Finite Element model of the face soft tissue is proposed to simulate the morphological outcomes of maxillofacial surgery. Three modelling options are implemented: a linear elastic model with small and large deformation hypothesis, and an hyperelastic Mooney-Rivlin model. An evaluation procedure based on a qualitative and quantitative comparison of the simulations with a post-operative CT scan is detailed. It is then applied to one clinical case to evaluate the differences between the three models, and with the actual patient morphology. First results shows in particular that for a “simple” clinical procedure where stress is less than 20%, a linear model seams sufficient for a correct modelling.

Simulation of the Exophthalmia Reduction Using a Finite Element Model of the Orbital Soft Tissues

This paper proposes a computer-assisted system for the surgical treatment of exophthalmia. This treatment is classically characterized by a decompression of the orbit, by the mean of an orbital walls osteotomy. The planning of this osteotomy consists in defining the size and the location of the decompression hole. A biomechanical model of the orbital soft tissues and its interactions with the walls are provided here, in order to help surgeons in the definition of the osteotomy planning. The model is defined by a generic Finite Element poro-elastic mesh of the orbit. This generic model is automatically adapted to the morphologies of four patients, extracted from TDM exams. Four different FE models are then generated and used to simulate osteotomies in the maxillary or ethmoid sinuses regions. Heterogeneous results are observed, with different backwards movements of the ocular globe according to the size and/or the location of the hole.

Computer aided planning for orthognatic surgery

A computer aided maxillofacial sequence is presented, applied to orthognatic surgery. It consists of 5 main stages: data acquisition and integration, surgical planning, surgical simulation, and per operative assistance. The planning and simulation steps are then addressed in a way that is clinically relevant. First concepts toward a 3D cephalometry are presented for a morphological analysis, surgical planning, and bone and soft tissue simulation. The aesthetic surgical outcomes of bone repositioning are studied with a biomechanical Finite Element soft tissue model.

A Finite Element Study of the Influence of the Osteotomy Surface on the Backward Displacement during Exophthalmia Reduction

Exophthalmia is characterized by a protrusion of the eyeball. The most frequent surgery consists in an osteotomy of the orbit walls to increase the orbital volume and to retrieve a normal eye position. Only a few clinical observations have estimated the relationship between the eyeball backward displacement and the decompressed fat tissue volume. This paper presents a method to determine the relationship between the eyeball backward displacement and the osteotomy surface made by the surgeon, in order to improve exophthalmia reduction planning. A poroelastic finite element model involving morphology, material properties of orbital components, and surgical gesture is proposed to perform this study on 12 patients. As a result, the osteotomy surface seems to have a non-linear influence on the backward displacement. Moreover, the FE model permits to give a first estimation of an average law linking those two parameters. This law may be helpful in a surgical planning framework.