A spatial model of the knee for the preoperative planning of knee surgery.

A model on the spatial mechanical behaviour of the passive knee is presented. The femoral articular surfaces were represented by generalized, sagittally elliptical, toroidal surfaces. The medial and lateral tibial articular surfaces were represented by a dished spherical surface and the lower hemihyperbolic region of a torus respectively. Anatomical articular cartilage, knee ligaments and the posterior capsule were represented by spring-like deformable elements with non-linear load versus deflection characteristics. All the forces that act on the femur relative to the tibia were represented by three orthogonal forces and three associated moments. Spatial, articulation-dependent femorotibial kinematic constraint equations of the passive knee were formulated in an analytically explicit manner, based on the natural coordinates of the articular surfaces. The constraint equations were solved algebraically in closed form. Equations were derived that describe spatial femoro-tibial motion, ligament length, ligament strain, ligament-based elastic potential energy and the quasi-static equilibrium of the passive knee. Software was written, simulations on the motion characteristics and load versus deflection characteristics of the knee were carried out and graphical results were presented. The simulation of planar flexion/extension was almost spontaneous. The time taken to simulate spatial six-degree-of-freedom femoro-tibial motion was less than 2.5 min. The models were found to be capable of representing real-life passive knees to a high degree of satisfaction. It has been demonstrated that the models can provide knee surgeons with additional information on major aspects of the preoperative planning of knee surgery. The models can be used to enhance the preoperative planning of ligament reconstruction, articular surfaces related surgery, osteotomy and patellar tendon transfer surgery.

A generic arthroscopy simulator architecture.

Virtual Environments offer considerable potential to improve training for arthroscopic surgery. However, current systems are developed for individual joints, which requires healthcare providers to purchase and maintain multiple environments with differing interfaces and capabilities. This paper describes a generic arthroscopy system architecture that allows the fast development of training environments for any joint, each sharing a common user-interface. The use of the architecture in developing a simple ankle simulator is also described.

Surgical trainee assessment using a VE knee arthroscopy training system (VE-KATS): experimental results.

Previous work has described the development of a Virtual Environment Knee Arthroscopy Training System (VE-KATS): a collaborative project between the Orthopaedic Department, Hull and East Yorkshire Hospitals NHS Trust, Hull, U.K., and the Department of Computer Science, University of Hull, U.K. This work describes the initial results obtained by Orthopaedic Surgical Trainees using VE-KATS. The results showed that differences between individual trainees could be measured using the scoring system incorporated within VE-KATS. There was a weak correlation with the seniority of the surgical trainees.

An efficient method for modelling soft tissue in virtual environment training systems.

Modelling soft tissues in virtual environment training systems is frequently required. The provision of both visually compelling and physically accurate models presents a number of problems for the developer. The Finite element technique presented in this paper, modal analysis, can be programmed to allow the user to easily trade-off accuracy of simulation for execution speed. It has been successfully used to produce simulations of the lateral meniscus on low powered portable computer systems.

A portable virtual environment knee arthroscopy training system with objective scoring.

We have developed a Virtual Environment Knee Arthroscopy Training System (VE-KATS). Formative analysis indicated several features which surgical trainees indicated were necessary for a system to be useful. We have addressed this need by incorporating both rigid and deformable objects, simultaneous use of camera and surgical instrument, improved optical modeling, portability and low cost. A major advance has been the incorporation of automated objective scoring of performance. VE-KATS has now progressed to a viable training system which will be of practical benefit to trainee orthopaedic surgeons.