Virtual reality (VR) techniques in orthopaedic research and practice.

Modeling the musculoskeletal joint system using biomechanical analysis and computer graphics techniques allows us to visualize normal, diseased and reconstructed joint function. This model can be used to study the loading of bones and joints under theoretical and simulated activities. In this study, intact cadavers were imaged using MRI, CT scanning and cryo-sectioning techniques. Using sequential pixel information of bone and soft tissue boundaries collected from digital camera images, MRI and CT scans, the volumetric models of the musculoskeletal joint system are reconstructed. "Descriptive geometry" techniques which treat bones as rigid bodies and cartilage, ligament and muscles as deformable bodies were used to construct the model. Joint resultant forces and moments were determined using an inverse dynamics formulation, while ligament tension, joint contact pressure, and bone stresses are solved through a simplified Rigid Body Spring Modeling technique and the Finite Element Method. The results under static and dynamic loading activities can be visualized using interactive computer graphics. The advantages of such a model are the elimination of the need for large numbers of intact cadaveric specimens, and the unprecedented capability to study joint loading responses under normal, abnormal and surgically reconstructed states. Such a model and its analytical capability are ideal for pre-operative planning and computer-assisted orthopaedic surgery. This Visual, Interactive, Computational, and Anatomic Model(VICAM) and its associated analysis capability represent the next generation of technology which will have an enormous impact in orthopaedic research, education and patient care.