Abstract
Advancements in knee replacement design, material and sterilisation processes have provided improved clinical results. However, surface wear of the polyethylene leading to osteolysis is still considered the longer-term risk factor. Experimental wear simulation is an established method for evaluating the wear performance of total joint replacements. The aim of this study was to investigate the influence of simulation input conditions, specifically input kinematic magnitudes, waveforms and directions of motion and position of the femoral centre of rotation, on the wear performance of a fixed-bearing total knee replacement through a combined experimental and computational approach. Studies were completed using conventional and moderately cross-linked polyethylene to determine whether the influence of these simulation input conditions varied with material. The position of the femoral centre of rotation and the input kinematics were shown to have a significant influence on the wear rates. Similar trends were shown for both the conventional and moderately cross-linked polyethylene materials, although lower wear rates were found for the moderately cross-linked polyethylene due to the higher level of cross-linking. The most important factor influencing the wear was the position of the relative contact point at the femoral component and tibial insert interface. This was dependent on the combination of input displacement magnitudes, waveforms, direction of motion and femoral centre of rotation. This study provides further evidence that in order to study variables such as design and material in total knee replacement, it is important to carefully control knee simulation conditions. This can be more effectively achieved through the use of displacement control simulation.
Highlights
Total knee replacement (TKR) is an increasingly common surgical intervention for the treatment of arthritis and joint degeneration.[1]
This effect was demonstrated through the computational contact modelling (Figure 5), and the direction of motion for the anterior– posterior (AP) input kinematics for the ISO position of the femoral centre of rotation (CoR) was reversed in order to maintain contact within the articulating region of the insert
The position of the femoral CoR and the input kinematics were shown to have a significant influence on the experimental wear rates of the GVF inserts (Figure 6) (p \ 0.05 analysis of variance (ANOVA))
Summary
Total knee replacement (TKR) is an increasingly common surgical intervention for the treatment of arthritis and joint degeneration.[1] Advancements in implant design, material and sterilisation processes have provided improved clinical results.[2,3] surface wear of the polyethylene leading to osteolysis is still considered the longer-term risk factor, as life expectancy and activity levels increase.[4]. Experimental wear simulation is an established method for evaluating the wear performance of total joint replacements, with numerous publications over the last decade demonstrating the influence of design, material, size and sterilisation processes on the performance of TKRs.[5,6,7,8,9,10,11,12,13] Experimental wear simulation under loading and motion representative of in vivo conditions is used to predict clinical wear performance. It has been shown that variation in the experimental conditions, such as kinematic inputs and component alignment, will have an impact on the wear performance of a TKR.[10,14,15,16]
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