What is the location and significance of the femoral tidemark in CORI planning?

What is the location and significance of the femoral tidemark in CORI planning?

• A. Location: most anterior point of wear; Significance: this is where distal femoral resection should begin.
• B. Location: most posterior point of the femur; Significance: CORI sizes the femoral implant based upon the distance between the most posterior point and the tidemark.
• C. Location: intercondylar eminence ridge; Significance: sizes the tibial implant.
• D. Location: tibial plateau center; Significance: used to calculate resection depth.

Answer: (A)

The key idea is that CORI planning uses the tidemark as a patient-specific landmark to guide the distal femoral cut. The tidemark is where cartilage wear ends and subchondral bone begins, and the most anterior point of wear marks where the native bone is exposed at the front of the knee. Starting the distal femoral resection from this anterior wear point ensures the cut lines up with the patient’s actual wear pattern, helping to recreate the correct extension space and enabling proper sizing and seating of the femoral component. If you were to use other landmarks, you’d be anchoring the femoral cut to areas not tied to the anterior wear boundary the planning relies on, which could misalign the joint line or affect gap balancing. The other landmarks mentioned align with different planning considerations (tibial sizing or different portions of the knee) rather than the femoral tidemark reference for the distal cut.

The key idea is that CORI planning uses the tidemark as a patient-specific landmark to guide the distal femoral cut. The tidemark is where cartilage wear ends and subchondral bone begins, and the most anterior point of wear marks where the native bone is exposed at the front of the knee. Starting the distal femoral resection from this anterior wear point ensures the cut lines up with the patient’s actual wear pattern, helping to recreate the correct extension space and enabling proper sizing and seating of the femoral component.

If you were to use other landmarks, you’d be anchoring the femoral cut to areas not tied to the anterior wear boundary the planning relies on, which could misalign the joint line or affect gap balancing. The other landmarks mentioned align with different planning considerations (tibial sizing or different portions of the knee) rather than the femoral tidemark reference for the distal cut.