Abstract
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.
Correspondence should be addressed to: Tim Wilton, BASK, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
