Significance of posterior condyle offset in total knee arthroplasty

Posterior condyle offset (PCO), firstly proposed by Bellmans in 2002, was thought to be associated with knee flexion after total knee arthroplasty (TKA) in the beginning. At present, four mainly methods have been widely used for measuring the PCO. X-ray is a simple and easy way, except for ignoring the asymmetry between medial and lateral femoral condyles, which leads to defects in principle. CT and MRI are not restricted by the projection angle, but the interferences of prosthetic metal artifacts cannot be ignored. Full-thickness cartilage-based posterior femoral condylar offset is the most accurate method, but the measurement is complicated and subjective. PCO has important clinical significance in TKA surgery. As for posterior cruciate ligament-retained TKA, the PCO affects the maximum knee flexion function by changing the radius of the rotation between femur and tibia. However, it doesn't happen in the posterior cruciate ligament replacement TKA, which may be related to the blocking of the soft tissue behind the knee and the restriction of the knee extension device. In addition, changes in PCO affect the flexion gap, which influences the stability of the knee joint, especially for flexion and mid-flexion. It also affects the anatomical structure and biomechanical structure of the knee joint, which may lead to osteolysis and early loosening. Excessive PCO increases the tension of the posterior joint capsule, resulting in a reduction of the extension gap, which brings the risk of knee flexion contracture. Therefore, it is necessary for physicians to restore the PCO to the preoperative state, in case of the occurrence of adverse consequences. This article summarized the clinical significance in TKA. Key words: Knee joint; Femur; Arthroplasty, replacement, knee