Simulateur collaboratif de chirurgie d'instrumentation du rachis scoliotique en réalité virtuelle: Étude de faisabilité

Patients suffering from a severe idiopathic scoliosis are subject to a highly invasive and risked instrumentation surgery. However, there is no collaborative training computer tool which simulates truthfully the experience of such a surgery and that allows a preoperative planning for a given patient. The objective of this research is to assess the feasibility of the development of such a simulator with the help of virtual reality technologies (CAVE and Immersadesk), a biomechanical modelling of the spinal column and collaborative functionalities. It also aims to determine if such a tool could be efficiently used for orthopaedist surgeons training during distance learning sessions.

These objectives justified the creation of a prototype, the Collaborative Virtual Reality Spine Surgery Simulator (CVrS3), which simulates a virtual surgery room where several surgeons, geographically away, can mutually see each other and collaborate during scoliosis spine surgery training sessions. The developed system is composed of a biomechanical collaborative server, a telepresence multi-users server and a virtual reality scoliosis spine surgery simulation client.

The biomechanical server uses the source code from the Spine Surgery Simulator (S3) software developed in the Laboratory of Biomechanical Modeling and Computer-Aided Surgery. This laboratory is shared by Ecole Polytechnique de Montreal and the Research Center of Sainte-Justine University Hospital Center. S3 is a spine surgery simulator for conventional computer allowing to test rapidly, before a real surgery, different intervention strategies for a given patient. S3 models the behavior of the scoliotic spine during instrumentation. The developed server adapts this modeling for a collaborative virtual reality use.

The telepresence multi-users server role is to propagate every participant movement to all the others. It permits the clients to move the user associated avatars inside the virtual surgery room. A better perception of participant's presence and intentions is then possible.

The simulation client is a three-dimensional graphic application that displays and manages an interactive virtual surgery room. It allows to move inside the room, to interact with objects (lamp, implants, tools, etc) and to perform surgical maneuvers on the scoliotic spine of a specific patient. Two versions were developed: immersive and non-immersive. The immersive version is made for advanced virtual reality systems such as the CAVE and the Immersadesk. The non-immersive version brings more flexibility by providing a conventional computer interface with keyboard and mouse.

This thesis introduces the architectural choices and features associated with the developed entities. A description of the user testing, performed with two orthopaedics specialists and three virtual environments specialists, is also provided. The tests allowed to assess drawbacks and benefits of the developed prototype. They also allowed to evaluate the potential usefulness of this type of simulator. The results from the tests are presented and commented.

This research proved the feasibility of the development of a virtual reality collaborative spine surgery simulator based on the most recent version of S3 biomechanical modeling. It also proved the superiority of virtual reality immersive systems against conventional interfaces based on simulation realism and easiness of interaction. The user testing, although of small scale, points out this kind of simulator could really be useful for resident general training, the understanding of the spine biomechanics, distance learning and training of the scoliosis spine surgery.