Where is the most posterior point of the femur located and why is it significant to CORI registration?

Where is the most posterior point of the femur located and why is it significant to CORI registration?

• A. Location: distal femoral tidemark; Significance: beginning resection.
• B. Location: intercondylar eminence ridge; Significance: rotation.
• C. Location: posterior condylar surface; Significance: CORI sizes the femoral implant based upon the distance between the most posterior point and the tidemark.
• D. Location: anterior tibial plateau; Significance: resection depth.

Answer: (C)

The most posterior point on the distal femur is the posterior condylar surface, which sits at the back edge of the femoral condyles. This landmark is used in CORI registration because the system sizes the femoral implant by measuring how far this posterior point sits from the tidemark—the line that marks the boundary between articular cartilage and calcified cartilage on the distal femur. That distance reflects the femur’s posterior offset, which is critical for choosing a component that fits the patient’s anatomy and preserves proper articulation and flexion. Using this measurement helps prevent issues like improper sizing, which could lead to overhang or undercoverage of the posterior aspect and affect knee kinematics. The other landmarks described don’t serve this sizing reference, and the tibial surface is not part of determining the femoral component size.

The most posterior point on the distal femur is the posterior condylar surface, which sits at the back edge of the femoral condyles. This landmark is used in CORI registration because the system sizes the femoral implant by measuring how far this posterior point sits from the tidemark—the line that marks the boundary between articular cartilage and calcified cartilage on the distal femur. That distance reflects the femur’s posterior offset, which is critical for choosing a component that fits the patient’s anatomy and preserves proper articulation and flexion. Using this measurement helps prevent issues like improper sizing, which could lead to overhang or undercoverage of the posterior aspect and affect knee kinematics. The other landmarks described don’t serve this sizing reference, and the tibial surface is not part of determining the femoral component size.