Low reproducibility of the intra-operative measurement of the transepicondylar axis during total knee replacement

Abstract

Background: The transepicondylar axis is often used for positioning of the femoral component in knee replacement.

Methods: We studied the reproducibility of the intra-operative palpation of the transepicondylar axis for rotational alignment of the femoral component in 20 total knee replacement (TKR) implantations with a non-image-based navigation system. 2 surgeons defined the transepicondylar axis 3 times each without changing the reference plane.

Results: The angle between the reference plane and the transepicondylar axis was measured by the navigation system. The mean intra-observer ranges of variation were 5 degrees and 6 degrees for both surgeons, with a maximum of 15 degrees. The mean inter-observer range of variation was 9 degrees, with a maximum of 15 degrees. Variations occurred in either internal or external rotation. Intra-observer agreement was considered good for one surgeon and poor for the other. There was no agreement between the two observers.

Interpretation: To define the rotational alignment of the femoral component of a TKR according to the intra-operative palpation of the transepicondylar axis may not be as reproducible as expected. However, the exact effect of this variability on the outcome after TKR should be studied.