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especially because most of the standard bony and ligamentous landmarks used during primaryTKR are lost due to the index implantation. However, as for primary TKR, restoration of thejoint line, adequate limb axis correction and ligamentous stability are considered critical for theshort- and long- term outcome of revision TKR. Navigation system might address this issue.MATERIAL AND METHODS: We are using an image-free system (ORTHOPILOT TM,AESCULAP, FRG) for routine implantation of primary TKR. The standard software was usedfor revision TKR. Registration of anatomic and cinematic data was performed with the indeximplant left in place. The components were then removed. New bone cuts as necessary wereperformed under the control of the navigation system. The system did not allow navigation forintra-medullary stem extensions and any bone filling which may have been required. Thistechnique was used for 37 patients. The accuracy of implantation was assessed by measuringfollowing angles on the post-operative long-leg radiographs: mechanical femoro-tibial angle,coronal orientation of the femoral component in comparison to the mechanical femoral axis,coronal orientation of the tibial component in comparison to the mechanical tibial axis, sagittalorientation of the tibial component in comparison to the proximal posterior tibial cortex.Individual analysis was performed as follows: one point was given for each fulfilled item,giving a maximal accuracy note of 4 points. Prosthesis implantation was considered assatisfactory when the accuracy note was 4 (all fulfilled items). The rate of globally satisfactoryimplanted prostheses and the rate of prostheses implanted within the desired range for eachcriterion were recorded. The results of the 37 navigated revision TKR were compared to 26cases of revision TKR performed with conventional intramedullary guiding systems.RESULTS: We observed a significant improvement of all radiological items by navigated cases.Limb alignment was restored in 82% of the navigated cases and 74% of the conventional cases.The coronal orientation of the femoral component was acceptable in 85% of the navigated casesand 76% of the conventional cases. The coronal orientation of the tibial component wasacceptable in 95% of the navigated cases and 89% of the conventional cases. The sagittalorientation of the tibial component was acceptable in 77% of the navigated cases and 66% ofthe conventional cases. Overall, 50% of the implants were oriented satisfactorily for the fourcriteria for navigated cases, and only 40% for conventional cases.DISCUSSION: The navigation system enables reaching the implantation goals for implantposition in the large majority of cases, with a rate similar to that obtained for primary TKA. Therate of optimally implanted prosthesis was significantly higher with navigation than withconventional technique. The navigation system is a useful aid for these often difficultoperations, where the visual information is often misleading.FiguresFigure 1 Figure 2file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]