Radiographic outcomes in the coronal plane with iASSIST™ versus optical navigation for total knee arthroplasty: A preliminary case-control study

BackgroundThe new navigation system iASSIST™ for total knee arthroplasty (TKA) relies on accelerometers and gyroscopes. The objective of this prospective study was to compare the accuracy of iASSIST™ to that of the conventional optical navigation system Navitrack™ by determining the rate of mechanical axis restoration (± 3°), postoperative mean mechanical alignment, rate of adequate femoral and tibial component positioning, mean operative time, and occurrence of navigation-related adverse events.HypothesisThe rate of mechanical axis restoration (± 3°) is not lower with iASSIST™ than with the conventional navigation system Navitrack™.Material and methodsOf 40 patients who underwent primary TKA between October 2013 and March 2014, 20 had navigation using iASSIST™ and 20 using Navitrack™. Six months after TKA, an independent observer measured three parameters on coronal radiographs: the hip-knee-ankle angle (HKA), the mechanical lateral distal femoral angle (mLDFA), and the mechanical medial proximal tibial angle (mMPTA).ResultsThe two groups showed no significant differences for the rates of HKA restoration (P = 0.3), adequate coronal positioning of the femoral component (P = 0.12) and tibial component (P = 0.12), or optimal success (P = 0.09). Significant differences in favour of iASSIST™ were demonstrated for the values and angular deviations of the HKA (P = 0.02) and mMPTA (P = 0.01), whereas no significant difference was found for mLDFA. There were no significant differences regarding the mean operative time (P = 0.06) or the occurrence of navigation-related adverse events (P = 0.18).DiscussionThe iASSIST™ system provides a neutral mechanical axis and optimal component position in the coronal plane in 95% of cases, indicating that it is as accurate as the optical navigation system Navitrack™.Level of evidenceIII, prospective case-control study.