What is true about the most posterior point of the tibia in CORI registration?

What is true about the most posterior point of the tibia in CORI registration?

• A. Location: posterior end of the tibial plateau; Significance: planning.
• B. Location: tidemark; Significance: planning.
• C. Location: intercondylar ridge; Significance: rotation.
• D. Location: posterior end of the tibial condyle; Best practice is to flex the knee and externally rotate the joint. Significance: Most challenging to capture. Not critical for system calculations.

Answer: (D)

In CORI registration, the most posterior point of the tibia is best associated with the posterior end of the tibial condyle. This location is both hard to capture—because it sits behind soft tissue and the bone contour—and challenging to visualize consistently, which is why precise identification during registration can be tricky. The recommended approach is to flex the knee and externally rotate the joint to open up that posterior region and make the landmark more reproducible. Importantly, this point is not central to the system’s calculations, so while it’s the most difficult to pin down, it isn’t critical for the core computations. Other proposed locations like the tidemark or the intercondylar ridge don’t correspond to the true posterior tibial landmark used in CORI registration, which is why the posterior end of the tibial condyle with the knee flexed and externally rotated is the best fit.

In CORI registration, the most posterior point of the tibia is best associated with the posterior end of the tibial condyle. This location is both hard to capture—because it sits behind soft tissue and the bone contour—and challenging to visualize consistently, which is why precise identification during registration can be tricky. The recommended approach is to flex the knee and externally rotate the joint to open up that posterior region and make the landmark more reproducible. Importantly, this point is not central to the system’s calculations, so while it’s the most difficult to pin down, it isn’t critical for the core computations. Other proposed locations like the tidemark or the intercondylar ridge don’t correspond to the true posterior tibial landmark used in CORI registration, which is why the posterior end of the tibial condyle with the knee flexed and externally rotated is the best fit.