False malalignment after computer-navigated total knee arthroplasty

Background: Although computer navigation has improved component alignment in total knee arthroplasty (TKA), radiographic outliers are reported with a wide range in literature even using this technique. We hypothesized that the postoperative malalignment after computer-navigated TKA was partially derived from the inherent problems with twodimensional (2D) measurement such as inaccuracies in measurement due to the knee position during the radiographic examination and the direction of the X-ray beam. We therefore conducted this study to determine how often knees with malalignment on 2D imaging were truly mal-aligned on three-dimensional (3D) reconstructed imaging. Methods: Sixty-two computer-navigated primary TKAs performed in 47 patients were included in this study. In all cases, a weight-bearing long-leg radiograph was obtained after TKA. 3D measurements were performed for outliers 2 degrees or more in coronal alignment of the femoral or tibial component. Results: For the 18 femoral mal-aligned components on 2D imaging, eight (44.4%) were not truly mal-aligned on 3D imaging (P = 0.0014). For the eight tibial mal-aligned components on 2D imaging, all knees (100%) were not truly mal-aligned on 3D imaging (P < 0.0001). Conclusions: A considerable number of the false malalignments were included on 2D measurement. Postoperative component alignment in the computer-navigated TKA might be much better than previously reported. (c) 2021 Elsevier B.V. All rights reserved. Computer-navigated total knee arthroplasty (TKA) was introduced with the intention of improving implant alignment with the hope that this would lead to improvement in clinical outcomes and implant survival [1-3]. However, despite having no outliers intra-operatively during computer-navigated TKA, radiographic outliers in coronal alignment are reported with a wide range in the literature [4]. In most cases, alignment after TKA was assessed using two-dimensional (2D) measurements with long-leg standing X