[CT analysis of leg alignment after conventional vs. navigated knee prosthesis implantation. Initial results of a controlled, prospective and randomized study]

Abstract

Introduction: Correct alignment of the leg is one of the significant factors for the outcome after TKA. Previous studies have shown that the use of a navigation system can improve the alignment. However, for the positioning of the femoral component no validated data are available. This article presents the first results of a controlled, prospective and randomised trial comparing navigation versus free-hand implantation in TKA with special reference to the rotation of the femoral component.

Methods: Since January 2003, all patients with primary arthrosis of the knee admitted to our hospital for TKA have been followed prospectively. For this first analysis, data were collected over a period of 5 months. Apart from the usual clinical evaluations, all patients had CT of the leg prior to the operation and 1 week postoperatively. Measurement of axis and rotation was performed by staff members of the X-ray department who had no knowledge of the operation technique (navigation vs. free-hand).

Results: Twenty five sets of CT scans have been analysed, from 12 navigated operations and 13 freehand procedures. All 12 of the navigated knees were within the interval of +/-3 degrees varus/valgus deviation, but only 8 of the 13 non-navigated knees met this criteria. The analysis of the rotation position of the femoral component revealed no difference between the two groups.

Conclusion: By using an intraoperative navigation system, the accuracy of the alignment in TKA can be improved. Long-term studies will have to be carried out to verify whether this will lead to a lasting benefit for the patient. Concerning the rotation position of the femoral implant, no conclusion can be made regarding the recommended rotation position at this point of the study.