Computer-assisted total knee arthroplasty: comparative results in a preliminary series of 72 cases

The aim of this study was to assess the value of navigation in achieving correct positioning of the implants and soft-tissue balance in total knee arthroplasty. We compared the axis alignment achieved in 72 LCS TKA's performed with navigation assistance to a historical cohort of 62 LCS TKA's implanted with the conventional instrumentation. The position of the tibial and femoral implants and the post-operative mechanical axes of the lower limbs were compared in the two series: there was a highly significant improvement in the alignment accuracy in the navigated series (p < 0.0001). There were no outliers in the computer-assisted series whereas 47% of the cases in the conventional series showed deviations of the mechanical axis of the lower limb of more than 2 degrees from neutral alignment. However, the position of the femoral implants in rotation was not improved, suggesting that there may be a need for a more refined technique for rotational alignment of the femur, which was based essentially in the present series on ligament balance in flexion. The height of the joint line was preserved in 89% of the cases, validating the empirical use of the spreader tool prototype used during the study. Navigation eases optimal ligament balancing, by providing information that is used for appropriate release of soft tissue to achieve the proper mechanical axis. No major complication related to the use of navigation was observed. Operation time was lengthened on average by 30 minutes. Long-term studies are necessary to show whether better accuracy in ligament balancing and higher precision in restoration of mechanical axes will improve the functional results and the survival rate of knee arthroplasty.