Image-guided reconstruction of the anterior cruciate ligament.

The replacement of the ruptured Anterior Cruciate Ligament (ACL) of the knee is a biomechanically difficult task. The correct placement of the graft, especially the isometry of the tibial and femoral insertion points, is critically to the success of the procedure. However, during arthroscopy, the planning of the insertion points and accurate execution of the plan is difficult. This paper reports an X-ray based system for navigation of the ACL graft implant. The system integrates arthroscopy and intra-operative X-ray imaging to identify the correct insertion points of the graft. Furthermore, it allows testing the isometry of these points before drilling of the femoral and tibial tunnel, and guides the drilling itself.

Effect of localization devices and registration methods on the accuracy of stereotactic frame systems predicted by the Gaussian approach.

A qualitative work-flow analysis of a neurosurgical procedure indicates that the resolution of the image used to plan the intervention is the major source of inaccuracy. Quantitative experimental measurements confirm this observation. They fail, however, to explain the relationship between the accuracy of the frame components involved in a stereotactic procedure and the overall application accuracy. This investigation shows that the novel Gaussian approach is a flexible framework for the calculation of the application accuracy of frame systems. Therefore, the Gaussian approach provides a detailed understanding of the interplay between the various factors affecting accuracy. The basic ideas and limitations of the Gaussian approach are briefly explained. The effect of fiducial marker distribution and registration is investigated and shown to introduce a spatial dependence to the accuracy. The results of the Gaussian approach are compared with experimental data for three stereotactic frame devices: Leksell G, Cosman-Roberts-Wells, and Brown-Roberts-Wells. Although the Gaussian approach is an approximation, it reproduces the accuracy measured in the experiment within the statistical error of that experiment.