• Jörg Lützner, Frank Krummenauer, Klaus-Peter Günther, and Stephan Kirschner.
• Department of Orthopaedic Surgery, University Hospital Carl Gustav Carus, Medical Faculty of the Technical University of Dresden, Dresden, Germany. Joerg.Luetzner@uniklinikum-dresden.de
• Bmc Musculoskel Dis. 2010 Jan 1; 11: 57.

BackgroundCorrect rotational alignment of the femoral and tibial component is an important factor for successful TKA. The transepicondylar axis is widely accepted as a reference for the femoral component. There is not a standard reference for the tibial component. CT scans were used in this study to measure which of 2 tibial landmarks most reliably reproduces a correct femoro-tibial rotational alignment in TKA.Methods80 patients received a cemented, unconstrained, cruciate-retaining TKA with a rotating platform. CT scans were performed 5-7 days postoperatively but before discharge. The rotational mismatch between the femoral and tibial components was measured. Furthermore, the rotational variance between the transepicondylar line, as a reference for the orientation of the femoral component and different tibial landmarks, was measured.ResultsThere was notable rotational mismatch between the femoral and tibial components. The median mismatch was 0 degrees (range: 16.2 degrees relative external to 14.4 degrees relative internal rotation of the femoral component).Using the transepicondylar line as a reference for femoral rotational alignment and the medial third of the tuberosity as a reference for tibial rotational alignment, 67.5% of all TKA had a femoro-tibial variance within +/- 5 degrees, 85% within +/- 10 degrees and 97.5% within +/- 20 degrees. Using the medial border of the tibial tubercle as a reference this variance was greater, only 3.8% had a femoro-tibial variance within +/- 5 degrees, 15% within +/- 10 degrees and 68.8% within +/- 20 degrees.ConclusionUsing fixed bone landmarks for rotational alignment leads to a notable variance between femoral and tibial components. Referencing the tibial rotation on a line from the medial third of the tibial tubercle to the center of the tibial tray resulted in a better femoro-tibial rotational alignment than using the medial border of tibial tubercle as a landmark. Surgeons using fixed bearings with a high rotational constraint between the inlay and the femoral component should be aware of this effect to avoid premature polyethylene wear.Trial RegistrationClinical trials registry NCT01022099.

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