Background: The goal of the current prospective randomised radiological study was to determine the accuracy of conventional and computer-assisted femoral component implantation in surface arthroplasty (SRA).

Methods: The standard implantation of SRA started at author’s institution in 2004; the learning curve lasted one year. From January 2006 have authors available a kinematic navigation system „Ci’ (DePuy International Ltd, Leeds, UK) for navigation of the femoral component of SRA „ASR’ (DePuy International Ltd, Leeds, UK). We analysed on standard radiographs the femoral component positioning after 30 conventionally instrumented (Group 1) and 30 navigated (Group 2) SRA femoral components. Posterolateral approach was used in all cases. The average age of 42 men and 18 women during surgery was 54? 8 (44–64) years; body mass index was 26,3? 3,7 (21,5–39,1) kg/cm2. We evaluated: varus or valgus orientation, horizontal femoral offset, and translation of the component.

Results: The varus-valgus positioning was more accurate in Group 2 (p < 0,05). The tendency to implant the femoral component in mild valgus position (2,8° in Group 1 compared to 2,1° in Group 2), more distally and ventrally in the femoral neck (in Group 1) and with femoral offset increase (4,8mm in Group 1 compared to 3,4mm in Group 2) was found. The femoral offset was restored more accurately in the navigated group (p < 0,05). The difference in component translation in relation to the femoral neck between both groups was statistically significant (p < 0,05) – it was more precise in the navigated group. No notching of the femoral neck was observed in both groups.

Conclusions: It is possible to achieve very accurate positioning of the femoral component with use of the ASR? manual tripod aiming device. But the navigation system enables a more accurate insertion of the femoral component. This benefit clearly weigh against an additional time cost of about 10 minutes because of navigation.