Kinematic analysis of leg alignment during conventional versus navigated total knee arthroplasty: initial results of a prospective study.

Current kinematic navigation systems provide real-time spatial analyses of leg alignments during total knee arthroplasty (TKA) instead of delayed radiographic verification after surgery. A prospective study was conducted to investigate leg alignments of TKAs that underwent different surgical guidance [intramedullary (IM) jig-based vs. navigation-assisted] using a kinematic navigation system. Since May 2007, patients admitted for primary TKA were considered for inclusion. Within 6 months, 38 sets of intraoperative analyses on the operated legs have been performed. Excluding seven unreliable data sets, 15 conventional IM jig-based TKAs and 16 navigation-assisted TKAs were available. The leg alignments in maximum knee extension were retrieved for comparison. Although similar final coronal alignments were accurately achieved in both groups (0.21 valgus in the IM group vs. 0.17 valgus in the NA group, p=0.993), a more flexed sagittal axis was constructed with conventional IM jigs (1.93 flexion in the IM group vs. 0.58 extension in the NA group, p<0.05). The study suggests that comparable coronal precision could be achieved with conventional IM jigs by trained surgeons, although computer-assisted navigation is a documented method to restore accurate alignment. Different sagittal alignments observed in this study indicate the inherent discrepancy between different surgical guides as well as their according concepts.