The anterior femoral cortical line (AFCL) is an anatomical landmark which has been used by the senior author for 20 years to assess femoral rotation in over 4000 TKR's. The AFCL describes the alignment of the anterior cortex of the distal femur proximal to the trochlear articular cartilage.

The AFCL was compared with the surgical epicondylar (SEA), anteroposterior (Whiteside's line) and posterior condylar (PC) axes using 50 dry-bone cadaveric femora, 16 wet cadaveric specimens, 50 axial MRI's and 58 TKR patients intra-operatively.

In the dry-bone/cadaveric femora (measuring relative to the SEA the AFCL and Whiteside's AP axis were 1° externally rotated and the PC axis was 1° internally rotated. By MRI (relative to the SEA) the AFCL was 8° internally rotated, Whiteside's was 2° externally rotated and the PC axis was 3° internally rotated. In the clinical study (measuring relative to a perpendicular to Whiteside's line alone) the AFCL was 4° degrees internally rotated, which equates to 2-3° of internal rotation relative to the SEA.

The AFCL is another axis, completing the ‘compass points’ around the knee. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma. We suggest building in 5° external rotation with respect to the anterior femoral cortical line for femoral component rotation.

Background: The purpose of this study was to assess the anterior femoral cortical line (AFCL) as an additional anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty. The AFCL was compared with the Epicondylar axis, the anteroposterior (AP) axis (Whiteside’s line), and the posterior condylar axis. Dry bone, cadaver, MRI and intra-operative measurements were compared.

Methods: Fifty dry bone femora, and 16 wet cadaveric specimens were assessed to identify the AFCL and this was compared against the 3 reference axes discussed above. Photographs were taken of the specimens with K-wires/marker pins secured to the reference axes and then a digital on-screen goniometer was used to determine the mean angular variations with respect to the Epipcondylar axis.

In the clinical trial, 58 consecutive patients undergoing total knee arthroplasty were included. After a routine exposure the AP axis was marked on each distal femur. The AFCL was then identified and the anterior femoral cortical cut was made parallel to this line. The angle between this cortical cut and the perpendicular to the AP axis was measured using a sterile goniometer.

In the MRI study, 50 axial knee images were assessed and the most appropriate slice/s determined in order to identify the AFCL and the other 3 reference axes and then their relationship was measured by an on-screen goniometer.

Results: In the cadaveric study the AFCL was a mean 1° externally rotated to the epicondylar axis (SD = 5°), White-side’s line was 1° externally rotated (SD = 4°) and the posterior condylar axis was 1° internally rotated (SD = 2°)

By MRI and with respect to the epicondylar axis, the AFCL was a mean 5° externally rotated (SD= 3), White-side’s Line was 1° externally rotated (SD = 2) and the posterior condylar axis was 3° internally rotated (SD = 2).

In the clinical study in 8 patients it was impossible to draw the AP axis because of dysplasia or destruction of the trochlea by osteoarthrosis. In the remainder the mean difference between the anterior femoral cortical line and Whiteside’s AP axis was 4.1 degrees internally rotated (SD = 3.8°). The lateral release rate for this cohort was 4%.

Conclusion: The anterior femoral cortical line provides an additional reference point, completing the ‘compass points’ around the knee. It has been shown in this study to be reliable in the laboratory, on MRI and in a clinical setting for assessing rotation of the femoral component. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma.

Purpose: To assess the anterior femoral cortical line (AFCL) as an additional anatomical landmark for determining intraoperative femoral component rotation in total knee arthroplasty. The anterior femoral cortical line (AFCL) is an anatomical landmark which has been used by the senior author for 20 years to assess femoral rotation in over 4000 TKRs. The AFCL describes the alignment of the anterior cortex of the distal femur proximal to the trochlear articular cartilage.

Methods: The AFCL was compared with the surgical epicondylar axis (SEA), anteroposterior axis (Whiteside’s line) and posterior condylar (PC) axis using 50 dry-bone cadaveric femora, 16 wet cadaveric specimens, 50 axial MRI scans and 58 TKR patients intra-operatively.

Results: In the dry-bone and cadaveric femora (measuring relative to the SEA) the AFCL and Whiteside’s AP axis were 1° externally rotated and the PC axis was 1° internally rotated. With MRI (relative to the SEA) the AFCL was 8° internally rotated, Whiteside’s was 2° externally rotated and the PC axis was 3° internally rotated. In the clinical study (measuring relative to a perpendicular to Whiteside’s line alone) the AFCL was 4° degrees internally rotated, which equates to 2–3° of internal rotation relative to the SEA.

Conclusion: The AFCL is another axis, completing the ‘compass points’ around the knee. It may prove particularly useful when one or all of the other reference axes are disturbed such as in revision TKR, lateral condylar hypoplasia or where there has been previous epicondylar trauma. We suggest building in 5° external rotation with respect to the anterior femoral cortical line when judging femoral component rotation.