Measuring tibial component rotation of TKA in MRI: What is reproducible?

• Correct rotational alignment of components is crucial for success of total knee arthroplasty (TKA).
• Defining landmarks on the tibia that allow for reproducible measurement of component rotation is challenging.
• This study is the first to compare the reproducibility of three different measurement techniques via MRI.
• Best reliability achieved with tibial epicondylar axis and posterior tibial margin; tibial tubercle was less reliable
• We suggest that all three reference lines are used for assessment of a painful knee following TKA

PurposeCorrect rotational alignment of components is crucial for the success of total knee arthroplasty (TKA). Defining landmarks on the tibia that allow for reproducible measurement of component rotation seems to be more challenging than on the femoral side. This study compares the reproducibility of three different measurement techniques.ScopeA magnetic resonance imaging (MRI) analysis of 55 patients following TKA was conducted. The rotation of the tibial components was determined using three different reference lines: a tangent to the posterior tibial margin, the tibial epicondylar axis, and the tibial tubercle. Data were analyzed for intra- and inter-observer reliability using intra-class correlation coefficients (ICCs), and a variance comparison between measurement techniques via F-test.ResultsHighest reliability and lowest variances for measurement of tibial component rotation were achieved by relation to the tibial epicondylar axis and posterior tibial margin. The tibial tubercle proved to be less reliable (ICC 0.632 (interobserver) and 0.526 (intraobserver)), and variances were significantly higher in comparison with the other two techniques.ConclusionBased on the presented MRI data, measurements of the tibial component rotation are done best using the posterior tibial margin and the tibial epicondylar axis. The tibial tubercle measurement proved to be less reliable for this purpose. We suggest that all three reference lines will be used for assessment of a painful knee following TKA to allow for informed decision making and for choice of best treatment options for the patient.Level II, clinical study.