The landmarks used to achieve correct rotational alignment of the
femoral component in total knee arthroplasty may be indistinguishable or
unreliable in the distal architecture of a valgus knee. Five observers
identified the anteroposterior axis, the posterior condylar axis, and the
transepicondylar axis in thirty cadaveric femora to determine the
reliability of the use of each axis in the operative setting. In addition,
radiographs were made of the distal aspect of each femur, the axes were
constructed, and the angles were measured and compared with the visual
measurements made by the observers. A line drawn perpendicular to the
anteroposterior axis consistently approximated 4 degrees of external
rotation relative to the posterior condylar surfaces. The transepicondylar
axis was more difficult to define and was not as accurate. The radiographic
results were similar to the visual results, but the standard deviations for
the former were less than those for the latter. The anteroposterior axis
appears to be a reliable landmark for rotational alignment of the femoral
component in a valgus knee.