Aims: Does CT-less navigation using the NAVITRACK-System improve post-operative rotational alignment of prosthesis compared to not-navigated implantation technique?

Methods: A total number of 250 patients was enrolled into a randomized mono-centre-study. Ninety patients received computer-aided-surgery (CAS), 160 patients received not-navigated implantation technique. Mechanical leg-/femur-/tibia-axes were identified using complete-leg-CT-scans. Rotational alignment was calculated measuring the angles formed between condylary and epicondylary axes (femoral), transverse tibia plateau axis and tibial tuberosity (tibial) respectively, by the use of coronar CT-scans. Knee Society – and SF-36-Scores were collected pre- and post-operatively at 6 weeks /6 months. Statistical analysis was performed by the chi-square-test.

Results: (All values in mean +− SEM (range)) A mechanical-axis-range of 180 +− 3 was achieved in 97,9% of navigated, and in 76,8% of the not-navigated patients. The tibial component was placed in a 2,1 +− 1,3 -varus-position in navigated patients. In the conventional patient group varus position was 1,8 +− 1,4. A 0,8 +− 1,5 femoral-valgus-position was found in navigated patients, respectively a 0,3 +− 2,7 varus-position in the not-navigated. The internal rotation (relative to epicondylar axis) of the femoral component was 2.8 +− 1,0 (0,7–3,8) in the CAS-group and 2.1 +− 1,5 (0–5,9) in the non-navigated. On the tibial side, the internal rotation of the plateau relative to tibial tuberosity was 20.5 +− 2.5 (16,8–24,8) in CAS- and 22.2 +− 7.5 (9,3–43,2) in the conventionally treated patients.

Conclusions: CT-less navigation using NAVITRACK was suitable to a.) reconstruct mechanical axis within the limits of 180° +− 3° and b.) reduce rotational malalign-ment especially on the tibia. The system may improve the survivorship of TKR as well as the functional outcome after implantation.