Bony landmarks for determining the mechanical axis of the femur in the sagittal plane during total knee arthroplasty.

Background: There is no accepted landmark for the mechanical axis of the femoral axis in sagittal plane in conventional total knee arthroplasty.

Methods: As palpable anatomic landmarks of the femur, lateral epicondyle, and anterior margin of the greater trochanter were identified. The line connecting these two landmarks was defined as the "palpable sagittal axis". The mechanical axis of the femur was compared with the palpable sagittal axis and the distal femoral anterior cortex axis. These axes were also compared with sagittal bowing of the femur.

Results: The distal femoral anterior cortex axis and the palpable sagittal axis were flexed by 4.1 degrees and 2.4 degrees more than the sagittal mechanical axes, respectively (p < 0.05). However, the palpable sagittal axis was not correlated with sagittal bowing of the femur (Spearman's rs, 0.17; p = 0.14).

Conclusions: The palpable sagittal axis showed a consistent relationship with the sagittal mechanical femoral axes regardless of the severity of the sagittal bowing of the femur.