A surface topographical analysis of explanted knee prostheses

Abstract

In 2017 there were 106,334 primary and 6,502 revision knee replacement surgeries reported in England, Wales, Northern Ireland and the Isle of Man. Annual increases of both procedures are predicted. Analyses of explanted orthopaedic prostheses enables greater understanding of their true clinical performance and can lead to design improvements, increased longevity and enhanced patient safety and benefit. This thesis provides a thorough investigation into the surface topographical analysis of explanted knee prostheses and the relationship between in vivo surface topographical changes and patient and implant demographics. This is the largest surface topographical analysis of explanted knee prostheses to date within the United Kingdom. This work is the first to report the surface roughness of explanted Unicondylar Knee Replacement (UKR) prostheses. Within this thesis, 135 knee prostheses were retrieved from revision surgery, processed for analysis and catalogued with patient data. Non-contacting profilometry and semi-quantitative damage scoring were used to analyse the surface topography of explanted and reference Total Knee Replacements (TKRs) and UKRs with cobalt chromium alloy (CoCr) and oxidised zirconium (OxZr) femoral components. All explanted femoral components showed an increase in surface roughness between 33% and 263% after time in vivo. There were no correlations found between the surface roughness and the damage scores recorded on the explanted prostheses or between the surface topography measurements and the duration in vivo, side of implantation or patient age, BMI or gender. No differences were found between in vivo surface topographical changes recorded on retrieved TKR compared with retrieved UKR components. No differences were found between in vivo surface topographical changes recorded on retrieved CoCr components compared with retrieved OxZr components. This work provides valuable data concerning the true in vivo performance of knee replacement prostheses and contributes to furthering the understanding of the mechanisms of failure of these prostheses.