Preoperative planned distance between the skin surface and the guide rod provides accurate posterior tibial slope in total knee arthroplasty.

ABSTRACT

BACKGROUND: Although sagittal tibial alignment in total knee arthroplasty (TKA) is important, no landmark exists to achieve reproducible slope. It is theoretically demonstrated that the preoperative planned distance between the skin surface and the rod can be a useful guide for the tibial slope in the previous imaging study. We conducted this retrospective study to confirm whether the results of the study are repeatable in an intra-operative situation. METHODS: Fifty-five consecutive TKAs using the distance from the extramedullary cutting guide rod to the skin surface as a reference guide for the tibial slope were performed and tibial component positioning was compared with 55 knees performed using the accelerometer-based portable navigation. The tibial component alignment was evaluated with a computed tomography (CT)-based three-dimensional (3D) software. RESULTS: The absolute mean deviation from the targeted slope in the proposed method was significantly smaller than the portable navigation (1.0° and 1.7°, respectively, p = 0.0025). The outlier rate beyond 3° was 0% in the proposed technique (16.4% in the portable navigation, p = 0.0014). CONCLUSIONS: The preoperative planned distance between the skin surface and the guide rod is a useful technique to provide accurate posterior tibial slope in TKA.