What Is the Incidence of Cobalt-Chromium Damage Modes on the Bearing Surface of Contemporary Femoral Component Designs for Total Knee Arthroplasty?

Background: The purpose of this study was to determine the incidence of metal release in contemporary total knee arthroplasty and the patient-related factors associated with this release. Methods: In total, 256 retrieved cobalt-chromium femoral components were collected through a multi-institutional orthopedic implant retrieval program (implanted: 1-15 years). Implants were mainly revised for loosening (84/256), instability (62/256), and infection (46/256). Third-body damage was assessed using a semiquantitative scoring method. Microscale electro-corrosion damage (MECD) was evaluated using digital optical microscopy. Radii of curvature were measured from representative components to calculate anterior-posterior and medial-lateral ratios. Femoral component surface roughness was measured using a white light interferometer. Using a multivariable linear model, associations between damage score, implant, and patient factors were tested. Spearman's rho correlation tests were performed to determine the association between roughness measurements and damage score. Results: Mild to severe damage was observed in 52% (134/256) of the components. In the multivariable linear model, anterior-posterior ratio (beta = -8.07; P < .001), loosening (beta = -0.52; P = .006), and patient weight (beta = 0.01; P = .007) were associated with damage score. Suspected MECD damage was observed in 82% (209/256) of components. The R-a value (rho = 0.196; P = .002) and R-q value (rho = 0.157; P = .012) increased as the damage score increased. Conclusion: The findings of this retrieval study support that similar damage mechanisms exist in contemporary and long-term total knee arthroplasty devices. Additionally, we observed associations between loosening, anterior-posterior conformity, and patient weight with increased surface damage. (C) 2018 Elsevier Inc. All rights reserved.