The effect of insert conformity and material on total knee replacement wear

Abstract

The mean average life is increasing; therefore, there is a need to increase the lifetime of the prostheses. To fulfil this requirement, new prosthetic designs and materials are being introduced. Two of the design parameters that may affect wear of total knee replacements, and hence the expected lifetime, are the insert conformity and material. Computational models have been used extensively for wear prediction and optimisation of artificial knee designs. The objective of the present study was to use a previously validated non-dimensional wear coefficient-based computational wear model to investigate the effect of insert conformity and material on the predicted wear in total knee replacements. Four different inserts (curved, lipped, partial flat and custom flat), with different conformity levels, were tested against the same femoral and under two different kinematic inputs (intermediate and high), with different levels of cross-shear. The insert bearing materials were either conventional or moderately cross-linked ultra-high molecular weight polyethylene (UHMWPE). Wear predictions were validated against the experimental data from Leeds knee simulation tests. The predicted wear rates for the curved insert (most conformed) were more than three times those for the flat insert (least conformed). In addition, the computationally predicted average volumetric wear rates for moderately cross-linked UHMWPE bearings were less than half of their corresponding conventional UHMWPE bearings. Moreover, the wear of the moderately cross-linked UHMWPE was shown to be less dependent on the degree of cross-shear, compared to conventional UHMWPE. These results along with supporting experimental studies provide insight into the design variables, which may reduce wear in knee replacements.

Manufacturing conditioned roughness and wear of biomedical oxide ceramics for all-ceramic knee implants

“…Similar results for increasing contact stress and decreasing wear rate by increasing the radial clearance have been found for hard-soft material combinations (CoCr-PE) [34-36]. Abdelgaied et al [34] showed by computational models of PE-inserts in total knee replacements that less conforming geometries had a lower predicted wear under both intermediate and high kinematics. The wear rates for the more conforming inserts were more than three times that for the less conforming insert.…”

A patient-specific wear prediction framework for an artificial knee joint with coupled musculoskeletal multibody-dynamics and finite element analysis

“…Thirdly, due to the lack of the relevant patient specific ligament properties, generic values were taken from the literature, and the ligament origin and insertion points were located manually to fit the patient's bone geometries according to anatomic descriptions. Fourthly, although the wear model has been verified with experiments [1,46,54], the predicted wear volumes were 31%-45% lower than the experimental results [32], and the experimental simulator results may be even smaller than the retrieved TKR [55]. The improvement of the wear model may provide an even more realistic coupled framework.…”

“…This wear model was used widely in wear prediction [1,46,47]. The wear model was based on the idea that wear volume (V) is proportional to the contact area (A) and sliding distance (S):…”

Computational Model Validation of Contact Mechanics in Total Ankle Arthroplasty

“…Wear and damage of polyethylene inserts in total joint arthroplasty (TJA) remain major factors that could lead to implant failure, potentially leading to implant loosening and revision in total ankle arthroplasty (TAA) . Contact mechanics at the metal–polyethylene articulation influence polyethylene wear . It is especially important in TAA due to the reduced size, and two to six times higher expected load at the ankle joint, compared with a hip or knee joint, respectively, which may contribute to the nearly double revision rate in TAA compared with hip or knee arthroplasties…”

“…Conflicting results have been reported on the correlation between polyethylene wear and metal–polyethylene congruency. Several studies have suggested increased wear with reduced conformity; while other studies have shown opposite trends . This may well be because polyethylene wear depends on multiple other factors such as sterilization method, component thickness, sliding distance, cross shear, and material properties.…”