Tribological performances of total knee prostheses: Roughness measurements on medial and lateral compartments of retrieved femoral components

Background: Total replacement of the knee joint is a well-established surgical procedure performed to relieve pain and to restore the functionality of a compromised knee. Nevertheless, wear is still one of the main issues affecting joint prostheses, causing loosening and, eventually, implants failure. Surface roughness of the implant has been found to influence the mechanisms for premature wear, having relevant influence on the tribological performance. Question: Joint load distribution have provided valuable insight into the knee loading patterns, showing that joint contact loads differ in medial and lateral condyles. We wondered if it is possible to find any alteration between surface roughness of medial and lateral sides and if the body mass index is in any way related to the in vivo roughening of the elements. Methods: For this purpose, 11 explants of total knee replacement (mean follow up of 3.2 years), with identical design, were analysed acquiring the roughness on the femoral components. Results: Macroscopic inspections show that lateral condyles underwent more surface damage than the medial ones. However, surface roughness was not significantly different comparing medial and lateral sides. Statistical tests outlined a significant difference in surface roughness when distinct sizes of implants, namely 3 and 4, are considered.