Integrating various common indexes of bony alignment in femoral supracondyle

Indexes, which can optimally represent the bony alignment around the knee, are still controversial. Three common indexes, mechanical axis (MA), anatomic axis (AA), and anatomic lateral distal femoral angle (aLDFA), were integrated to simplify patient follow-up in the femoral supracondylar region.

Eighty consecutive adult patients (40 men, 40 women; age range 19-40 years) were studied using a full-length standing scanogram. Thirteen indexes, including MA, AA, and aLDFA, were measured and integrated. The relationships among these indexes were analyzed.

The MA of the lower extremity passed with an average of 6.6 mm (9.2% of the tibial articular surface width) medial to the knee center. The supracondylar axis (SA) was an average of 2.0° more valgus than the AA in the femoral supracondyle. An average 1.1° deviation was noted in the AA, as measured by the femoral shaft axis or a line connecting the piriformis fossa to the knee center.

The femoral MA may be more favorable than the MA of the lower extremity in order to represent an ideal weight-bearing line. The AA and aLDFA may be measurable via the SA in the anteroposterior view of the plain knee radiograph. Thus, patient follow-up becomes much more convenient.