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NAVIGATED REVISION TOTAL KNEE REPLACEMENT

Hôpitaux Universitaires de Strasbourg, France

Revision TKR is a challenging procedure, especially because most of the standard bony and ligamentous landmarks are lost due to the primary implantation. However, as for primary TKR, restoration of the joint line, adequate limb axis correction and ligamentous stability are considered critical for the short- and long-term outcome of revision TKR. There is no available data about the range of tolerable leg alignment after revision TKR. However, it is logical to assume that the same range than after primary TKR might be accepted, that is ± 3° off the neutral alignment. One might also assume that the conventional instruments, which rely on visual or anatomical alignments or intra- or extramedullary rods, are associated with significant higher variation of the leg axis correction.

We used an image-free system (ORTHOPILOT TM, AESCULAP, FRG) for routine implantation of primary TKA. The standard software was used for revision TKA. Registration of anatomic and kinematic data was performed with the index implant left in place. The components were then removed. New bone cuts as necessary were performed under the control of the navigation system. The size of the implants and their thickness was chosen after simulation of the residual laxities, and ligament balance was adapted to the simulation results. The system did not allow navigation for centromedullary stem extension and any bone filling which may have been required. This technique was used for 54 patients. The accuracy of implantation was assessed by measuring the limb alignment and orientation of the implants on the post-operative radiographs.

Limb alignment was restored in 88%. The coronal orientation of the femoral component was acceptable in 92% of the cases. The coronal orientation of the tibial component was acceptable in 89% of the cases. The sagittal orientation of the tibial component was acceptable in 87% of the cases. Overall, 78% of the implants were oriented satisfactorily for the five criteria.

The navigation system enables reaching the implantation objectives for implant position and ligament balance in the large majority of cases, with a rate similar to that obtained for primary TKA. The navigation system is a useful aid for these often difficult operations, where the visual information is often misleading. The navigation system used enables facilitated revision TKA.

Correspondence should be addressed to Mr K Deep, General Secretary CAOS UK, Dept of Orthopaedics, Golden Jubilee National Hospital, Glasgow G81 4HX, Scotland. Email: caosuk{at}gmail.com