The femoral sulcus in total knee arthroplasty: reply to the letter by J.‐Y. Jenny

Dear Editors,We would like to thank Dr Jenny for the valid pointsraised regarding our article [1].All patients at surgery had an intact and identiableposterior cruciate ligament, and the functional midline ofthe sulcus in exion was dened as the anterior and lateralintercondylar edge of the PCL attachment to the femurafter the removal of synovial membrane and adjacent softtissues. This site was clearly and accurately identied. Thepoint is well taken that identication of the deepest part ofa shallow sulcus is prone to error.We felt the relevance to be that for ideal patellartracking, the prosthetic trochlea should be centred over thispoint on the native trochlea.Generally, the femoral component will be placed overthe centre of the resected bone, and if this lies up to 4 mmlateral to the native anatomical point, then it will implysome patellar mal-tracking. If replacing the patella, thenthe component position can be adjusted to account for thatposition. However, if the patellar is not resurfaced, then itis more important to centre the prosthetic trochlea over thenative trochlea.An alternative is to shift the position of the femoralcomponent but this may then create some condylar overlapat the margins, which may then necessitate a narrowcomponent.The small magnitude of the mean difference betweenthe location of the sulcus and the midline of the distalfemoral resection reects the observation that in mostpatients that point lies at or slightly lateral to the midline ofthe distal femoral resection. However, in some patients,variation of up to 4 mm from the midline was observed,which the surgeon may need to be aware of, because of theconsequences for patellofemoral kinematics.Reference