[CT-based and CT-free navigation in knee prosthesis implantation. Results of a prospective study].

INTRODUCTION: Accurate leg alignment is one important factor for long-term survival in total knee arthroplasty (TKA). The classical surgeon-controlled technique is associated with a deviation of the leg axis of more than 3 degrees in up to 30% of cases, regardless of the surgeon's experience. The aim of this study was to test the efficiency of a CT-based and CT-free navigation system in restoration of the leg axis.

METHOD: 100 TKA (PFC-Sigma, DePuy) were implanted either using the CT-based or CT-free module of the Vector-Vision navigation System (BrainLAB). There were no significant differences between the groups in preoperative leg deformity. Accuracy of implantation was determined on postoperative long-leg coronal and lateral X-rays.

RESULTS: A postoperative leg axis between 3 degrees varus and 3 degrees valgus was obtained in 46 patients (92%) in the CT-based group (A) and in 48 patients (96%) in the CT-free group (B). No significant differences were found for varus / valgus orientation (+/-3 degrees ) of the femoral (A=96%; B=94%) and tibial (A and B each 98%) components.

CONCLUSION: The use of the CT-based and CT-free Vector-Vision system allows a significant improvement in the accuracy of implantation in TKA. The CT-based module has the advantage of precise preoperative planning. On the other hand there are additional costs and time-consuming logistics. The advantages of the CT-free module are the intraoperative visualisation of the leg axis, the ligament balancing and joint kinematics. Cutting errors can be detected and corrected with both modules.