Physiologically shaped knee arthroplasty induces natural roll-back

Abstract

After total knee replacement the persistence of pain represents a significant problem. In this study, a novel knee arthroplasty (Aequos G1 knee arthroplasty) is investigated that was designed to replicate main features of human knee morphology to reduce the periodically occurring pain after knee replacement. Previous work showed theoretically that this arthroplasty design may reconstruct the four-bar linkage mechanism as it occurs in human knee by contriving a convex lateral tibial compartment and a sagittal offset of the centre of the medial and lateral femur condyles -inducing a roll-back mechanism as it exists in human. The aim of this study was to determine whether this potential roll-back mechanism can be confirmed by in-vivo measurements. This retrospective study showed that the patellar tendon angle decreases during flexion of 0.21 • per degree of flexion on average in the 16 knees studied. This amount is similar to physiological knee kinematics and in contrast to existing results in the literature after implantation of conventional total knee replacements which lack physiological knee kinematics. The results suggest that physiological motion after implantation of the Aequos G1 knee arthroplasty occurs during loaded motion up to approximately 45 • knee flexion.

The effect of total knee geometries on kinematics: An experimental study using a crouching machine

“…In a large cohort of bilateral total knee arthroplasties, patients reported a preference for this design compared with CR and PS designs, though more studies are needed to confirm this 24 . Other asymmetric guided motion knee designs have been developed, with condylar shapes which mimic normal knee geometry, or which reproduce normal laxity and stability, but their clinical effectiveness have not yet been investigated 25‐29 …”

“…have not yet been investigated. [25][26][27][28][29] The purpose of this study was to compare the effect of TKA component geometries on knee kinematics. We hypothesized that the kinematics of the condylar type knees would not resemble anatomic kinematics, would be similar between the different variations, and would be primarily controlled by the tibial rather than the femoral geometry; but that the kinematics of the medial pivot and guided motion knees would be similar to anatomic knee kinematics.…”