Orbital and Maxillofacial Computer Aided Surgery: Patient-Specific Finite Element Models To Predict Surgical Outcomes

摘要

This paper addresses an important issue raised for the clinical relevance ofComputer-Assisted Surgical applications, namely the methodology used toautomatically build patient-specific Finite Element (FE) models of anatomicalstructures. From this perspective, a method is proposed, based on a techniquecalled the Mesh-Matching method, followed by a process that corrects meshirregularities. The Mesh-Matching algorithm generates patient-specific volumemeshes from an existing generic model. The mesh regularization process is basedon the Jacobian matrix transform related to the FE reference element and thecurrent element. This method for generating patient-specific FE models is firstapplied to Computer-Assisted maxillofacial surgery, and more precisely to theFE elastic modelling of patient facial soft tissues. For each patient, theplanned bone osteotomies (mandible, maxilla, chin) are used as boundaryconditions to deform the FE face model, in order to predict the aestheticoutcome of the surgery. Seven FE patient-specific models were successfullygenerated by our method. For one patient, the prediction of the FE model isqualitatively compared with the patient's post-operative appearance, measuredfrom a Computer Tomography scan. Then, our methodology is applied toComputer-Assisted orbital surgery. It is, therefore, evaluated for thegeneration of eleven patient-specific FE poroelastic models of the orbital softtissues. These models are used to predict the consequences of the surgicaldecompression of the orbit. More precisely, an average law is extrapolated fromthe simulations carried out for each patient model. This law links the size ofthe osteotomy (i.e. the surgical gesture) and the backward displacement of theeyeball (the consequence of the surgical gesture).