Background: Several reference axes are used to establish femoral
rotational alignment during total knee arthroplasty, but debate continues with
regard to which axis is most accurately and easily identified during surgery.
Computer-assisted navigation systems have been developed in an attempt to more
accurately and consistently align implants during total knee arthroplasty, but
it is unknown if navigation systems can improve the accuracy of femoral
rotational alignment as compared with that achieved with more traditional
techniques involving mechanical guides. The purposes of the present study were
to characterize the variability associated with femoral rotational alignment
techniques and to determine whether the use of a computer-assisted surgical
navigation system reduced this variability.
Methods: Eleven orthopaedic surgeons used five alignment techniques
(including one computer-assisted technique and four traditional techniques) to
establish femoral rotational alignment axes on ten cadaveric specimens, and
the orientation of these axes was recorded with use of a navigation system.
These derived axes were compared against a reference transepicondylar axis on
each femur that was established after complete dissection of all soft
Results: There was no difference between the mean errors of all five
techniques (p > 0.11). Only 17% of the knees were rotated <5° from
the reference transepicondylar axis, with alignment errors ranging from
13° of internal rotation to 16° of external rotation. There were
significant differences among the surgeons with regard to their ability to
accurately establish femoral rotational alignment axes (p < 0.001).
Conclusions: All techniques resulted in highly variable rotational
alignment, with no technique being superior. This variability was primarily
due to the particular surgeon who was performing the alignment procedure. A
navigation system that relies on directly digitizing the femoral epicondyles
to establish an alignment axis did not provide a more reliable means of
establishing femoral rotational alignment than traditional techniques did.