Biomechanical Consequences of Anterior Femoral Notching in Cruciate-Retaining Versus Posterior-Stabilized Total Knee Arthroplasty

Anterior femoral notching during total knee arthroplasty is a potential risk factor for periprosthetic supracondylar femur fracture. We conducted a study to determine if the design of the femoral implant changes the risk for periprosthetic supracondylar femur fractures after anterior cortical notching. An anterior cortical defect was created in 12 femoral polyurethane models. Six femora were instrumented with cruciate-retaining implants and 6 with posterior-stabilized implants. Each femur was loaded in external rotation along the anatomical axis. Notch depth and distance from anterior cortical notch to implant were recorded before loading, and fracture pattern was recorded after failure. There were no statistically significant differences in notch depth, distance from notch to implant, torsional stiffness, torque at failure, final torque, or fracture pattern between cruciate-retaining and posterior-stabilized femoral component designs. Periprosthetic fracture after anterior femoral notching is independent of the bone removed from the intercondylar notch. After notching, there likely is no significant difference in femoral strength in torsion between cruciate-retaining and posterior-stabilized designs.