Precise bone preparation is a key element for the successful long-term fixation of orthopaedic implants. Initial stability leading to reduced micromotion and direct apposition of the bone against the implant are mainly responsible for proper load transfer and bone remodeling. The fit and fill of the implant is created by shaping and sizing a cavity within the bone to accommodate the implant, which is usually accomplished by standard machining operations such as broaching, milling and drilling. This paper presents our initial study of developing a bone drilling simulation system, with the goal of guiding a novice surgeon to practice the bone drilling operation. A virtual reality approach is taken to provide force feedback, in order to make the simulation system more intuitive and interactive. Octree is used to organize and manipulate the volumetric data representing the bone model. Adaptive surface rendering is chosen as the graphics display algorithm. Multithreading is used to address the different update rates required in the real-time graphic and haptic displays.

We present the development of a bone drilling simulation system to simulate on a PC the drilling operations commonly used in orthopedic surgery. A drilling force model is obtained by performing regression of measured drilling force versus process and material parameters. A haptic rendering algorithm consisting collision detection and force generation is also developed. The overall simulation of the developed system runs two threads in parallel: (1) haptics thread, which obtains the position and orientation of the virtual drill and provides force feedback and (2) graphics thread, which is dedicated to real-time rendering of volumetric data.

This paper describes image processing, geometric modeling and data management techniques for the development of a virtual bone surgery system. Image segmentation is used to divide CT scan data into different segments representing various regions of the bone. A region-growing algorithm is used to extract cortical bone and trabecular bone structures systematically and efficiently. Volume modeling is then used to represent the bone geometry based on the CT scan data. Material removal simulation is achieved by continuously performing Boolean subtraction of the surgical tool model from the bone model. A quadtree-based adaptive subdivision technique is developed to handle the large set of data in order to achieve the real-time simulation and visualization required for virtual bone surgery. A Marching Cubes algorithm is used to generate polygonal faces from the volumetric data. Rendering of the generated polygons is performed with the publicly available VTK (Visualization Tool Kit) software. Implementation of the developed techniques consists of developing a virtual bone-drilling software program, which allows the user to manipulate a virtual drill to make holes with the use of a PHANToM device on a bone model derived from real CT scan data.

Bone surgery simulation enhanced by virtual reality technology is an effective means of training and educating novice surgeons to practice common bone surgery procedures such as drilling, cutting, etc. Haptic rendering is an essential part of the development of a bone surgical simulation system. Visual displays augmented by haptic feedback provide more realistic virtual environments, thus allowing the trainee to get a realistic feel of the real-world surgery process. This paper presents our research on the development of a bone surgery simulation system, especially on the development of the haptic rendering. Our objective is to provide a high level of realism of haptic rendering, thus making the virtual surgery procedures as intuitive and interactive as the real-world surgery procedures. In order to achieve the real-time performance of the simulation system, a Divide-and-Conquer method has been introduced in the geometric modeling to manipulate the large dataset required by the surgery simulation system. A force model based on the volumetric representation of the bone geometry has been developed. Also a running time delay technique has been developed to address the vibration problem in the haptic display. The PHANToMTM desktop manipulator is used as an input device to locate the position and orientation of a virtual drill. It is also used as an output device to provide the user with haptic sensation during the drilling operation.

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