Joint distraction force changes the three-dimensional articulation of the femur and tibia in total knee arthroplasty: a cadaveric study

Purpose The purpose of this study was to test the hypotheses that the joint distraction force changes the three-dimensional articulation between the femur and the tibia and that the presence of posterior cruciate ligament (PCL) affects the three-dimensional articulation during joint gap evaluation in total knee arthroplasty (TKA). Methods Cruciate-retaining TKA procedures were performed on 6 cadaveric knees using a navigation system. The joint center gap and varus ligament balance were measured using Offset Repo-Tensor ® with the knee at 90° of flexion before and after PCL resection for joint distraction forces of 89, 178, and 266 N. The three-dimensional location of the tibia relative to the femur and the axial rotational angle of the tibia were also assessed. Results Regardless of PCL resection, the joint center gap became larger ( p = 0.002, p = 0.020) and varus ligament balance became more varus ( p = 0.002, p = 0.002) with increasing joint distraction force, whereas the tibia was more internally rotated ( p = 0.015, p = 0.009) and more anteriorly located ( p = 0.004, p = 0.009). The tibia was more internally rotated ( p = 0.015) and more posteriorly located ( p = 0.026) after PCL resection than before resection. Conclusions Joint distraction force changed three-dimensional articulation regardless of PCL preservation. PCL function was revealed as a factor restraining both tibial posterior translation and internal rotation. Surgeons should recognize that joint gap evaluation using a tensor device is subject to three-dimensional changes depending on the magnitude of the joint distraction force.