Review Question - QID 351

Understanding flexion/extension gaps in total knee arthroplasty is paramount to patient success. Treatment for flexion instability consists of either increasing the size of the femoral component, shifting the femoral component posteriorly, or increasing the size of the polyethylene and then dealing with the tight extension gap.

As discussed by Ries et al, increasing the size of the femoral component will change the anterior/posterior size of the component without changing the proximal/distal size of the component, thus changing only the flexion gap. With upsizing the femoral component, you will likely have to add augments as the bone cut will not match a larger component. Moving the femoral component more posterior will accomplish the same goal of decreasing only the flexion gap. Increasing the poly thickness will change both the flexion and extension gaps, and in this patient, the surgeon would then have to address the tight extension gap by resecting more distal femur and/or releasing the posterior capsule.