Femoral component rotation in total knee arthroplasty: an MRI-based evaluation of our options.

Proper femoral component rotation is crucial in successful total knee arthroplasty. Rotation using anatomic landmarks has traditionally referenced the transepicondylar axis (TEA), Whiteside's Line (WSL), or posterior condylar axis (PCA). TEA is thought to best approximate the flexion-axis of the knee, however WSL or PCA are common surrogates in the operating room. This study evaluated 560 knees using MRI-based planning software to assess the relationship of WSL and PCA to the TEA and determine if the relationships were influenced by pre-operative coronal deformity. Results showed the WSL-TEA relationship has more variability than PCA-TEA and that the PCA is more internally rotated in females and valgus knees. Axis options and historical assumptions about axis relationships may need to be reassessed as imaging technology advances.