[CT analysis of leg alignment after conventional vs. navigated knee prosthesis implantation. Initial results of a...

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.

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).

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.

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.