Abstract
Introduction: The achievement of a well aligned limb is one of the main factor that probably affect the long term survival of total knee arthroplasty. Despite many improvements in ancillary device design, a significant number of total knee arthroplasty remain in excessive varus or valgus. Computer assisted systems may improve the control on implant positioning. The goal of this paper is to present the rationale and the early experience with a recently developed system (Navitrack®).
Material and methods: A CT-scan allows acquisition of patient anatomy. The 3D reconstruction is obtained with specially developed software. Location of the instruments and bone during surgery is obtained either with a magnetic or an optical system. After captor placement, navigation allows real-time control of the ancillary device in order to perform the necessary cuts. The main landmarks given by the system during surgery are the femoral and tibial mechanical axis, cuts location, rotational positioning of the femoral implant can also be controlled using the transepicondylar axis, the posterior aspects of the femoral condyles, or the patellar groove. Rotational positioning of the tibial component can also be evaluated in order to allow a adequate orientation of the tibial slope.
Results: Four implantations failed for technical reasons including failure of captor fixation on bone during surgery, and failure of the electronic control of the captors. However, most attempted implantations were successful with an accurate placement of the implants evaluated on long leg radiographs.
Discussion: Implantation of a TKA with an anatomic-based system is possible. But, this first encouraging experience needs to be confirmed and improvements are in progress.
The abstracts were prepared by Orah Naor. Correspondence should be addressed to him at the Israel Orthopaedic Association, PO Box 7845, Haifa 31074, Israel.
