Objectives: In the literature only a few studies describe inter-individual reproducibility for the selection of anatomical landmarks for Total Knee Arthroplasty [1,2]. This paper describes the reliability for identifying the femoral epicondyles with the use of a very accurate Navigation measuring device. Background: Femoral component malalignment after total knee arthroplasty (TKA) is known to cause clinical symptoms, such as anterior knee pain. For intraoperative referencing several anatomical landmarks are used by the surgeons. One of the most applied landmarks is the transepicondylar axis (TEA). Material and Methods: Six human cadavers were selected randomly. Four surgeons performed selections of the most prominent points of the medial and lateral epicondyle six times in each cadaver to determine the TEA. Each individual position of the most prominent epicondyle points was digitized and recorded by an accurate optical navigation system. The most prominent points of the medial and lateral epicondyle of all knee specimens were also defined in CT and its coordinates recorded as CT entry points. The position of the manually selected points to the CT entry points and the resulting area of distribution of entry points were calculated. Results: The overall distribution of selected points was located in an area of 278mm2 around the medial epicondyle and 298mm2 of the lateral. In a second step, a matrix with the dimension of the calculated area of distribution was marked upon the epicondyles of a saw bone. Each possible connection of lateral and medial points of the matrix resulted in a different TEA and femoral component rotation. The maximum possible rotation of femoral components based on TEAs resulting from selecting the points within the above areas was about 9掳 for both external and internal rotation.
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