Improved 3D Osteotomy Planning in Cranio-maxillofacial Surgery

Digital three-dimensional image fusion processes for planning and evaluating orthodontics and orthognathic surgery. A systematic review

The three important tissue groups in orthognathic surgery (facial soft tissues, facial skeleton and dentition) can be referred to as a triad. This triad plays a decisive role in planning orthognathic surgery. Technological developments have led to the development of different three-dimensional (3D) technologies such as multiplanar CT and MRI scanning, 3D photography modalities and surface scanning. An objective method to predict surgical and orthodontic outcome should be established based on the integration of structural (soft tissue envelope, facial skeleton and dentition) and photographic 3D images. None of the craniofacial imaging techniques can capture the complete triad with optimal quality. This can only be achieved by 'image fusion' of different imaging techniques to create a 3D virtual head that can display all triad elements. A systematic search of current literature on image fusion in the craniofacial area was performed. 15 articles were found describing 3D digital image fusion models of two or more different imaging techniques for orthodontics and orthognathic surgery. From these articles it is concluded, that image fusion and especially the 3D virtual head are accurate and realistic tools for documentation, analysis, treatment planning and long term follow up. This may provide an accurate and realistic prediction model.

Three-dimensional surgical simulation

In this article, we discuss the development of methods for computer-aided jaw surgery, which allows us to incorporate the high level of precision necessary for transferring virtual plans into the operating room. We also present a complete computer-aided surgery system developed in close collaboration with surgeons. Surgery planning and simulation include construction of 3-dimensional surface models from cone-beam computed tomography, dynamic cephalometry, semiautomatic mirroring, interactive cutting of bone, and bony segment repositioning. A virtual setup can be used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with a computer display showing jaw positions and 3-dimensional positioning guides updated in real time during the surgical procedure. The computer-aided surgery system aids in dealing with complex cases with benefits for the patient, with surgical practice, and for orthodontic finishing. Advanced software tools for diagnosis and treatment planning allow preparation of detailed operative plans, osteotomy repositioning, bone reconstructions, surgical resident training, and assessing the difficulties of the surgical procedures before the surgery. Computer-aided surgery can make the elaboration of the surgical plan a more flexible process, increase the level of detail and accuracy of the plan, yield higher operative precision and control, and enhance documentation of cases.

Finite element modelling of maxillofacial surgery and facial expressions--a preliminary study

BACKGROUND

Recent advances in diagnostic imaging and associated software have enabled the transformation of anatomical structures into finite element (FE) models facilitating computerized facial modelling. The work presented employs personalized imaging data of facial anatomical structures for use in planning and predicting the outcome of maxillofacial surgery. The current process relies on either freehand planning and/or commercial two-dimensional (2D) and three-dimensional (3D) surgical planning software packages, but the validity of these software packages has been questioned. In this paper, the finite element technique was used to predict the outcome of maxillofacial surgery.

METHODS

A finite element facial model was created, based on patient specific bone and skin image data, combined with generic muscle data. The model was used for two distinct purposes: simulation of the maxillofacial surgery and simulation of facial expressions pre- and post-surgery. This combination allowed for an improved prediction of surgery outcome. Commercial software was used for creating the FE facial model from the original image data, and LS-DYNA(®) was the analysis code used for the purpose of the FE simulation.

RESULTS

The results from the simulation of maxillofacial surgery showed an overall agreement of 85% with the patient data at 6 months post-surgery and the error was generally contained within a ± 2 mm threshold.

CONCLUSIONS

The results show that the approach of using commercial FE software tools to create a detailed and anatomically accurate patient specific model for simulation of maxillofacial surgery, as well as facial expressions, can be applied in facial surgery planning. As the study was based on data collected from one patient, further work is needed in which additional subjects can be assessed.