The linea aspera as a rotational landmark: an anatomical MRI-based study.

Abstract

The linea aspera can be used as a landmark to assess the rotation of the distal femoral epiphysis when performing an endoprostheses. However, no study has assessed the reliability of this landmark. We therefore asked whether the linea aspera could be used as a rotational landmark for positioning distal femoral knee megaprostheses. This is an anatomic MRI-based study of 50 femurs (27 subjects). For each femur, multiple axial sections were obtained from the intercondylar line at the knee joint to the lesser trochanter; each axial section was superposed with that where the posterior condyles were seen and the R angle was measured. The R angle is the angle measured medially where the line passing through the linea aspera and the line tangent to the posterior condyles intersects. There were considerable differences between and within subjects with a maximum R angle ranging from 100° to 120°. Regression models showed that the R angle was significantly associated with distance from knee joint and subjects. Surgeons should have the R angle measured before performing a distal femoral reconstruction.