Micro-computed tomography for non-destructive testing of ceramic knee implants

Abstract

Introduction: There are many reasons for the failure of a total knee endoprosthesis. The most common are infection, loosening, instability, pain and abrasion of the polyethylene. It is therefore necessary to further develop the current models. This study examines a new completely metal-free ceramic total knee endoprosthesis. There are several reports on the clinical results and biomechanical testings. Non-destructive analysis by computed tomography (CT) is a new tool for analysis of a ceramic knee endoprosthesis. Methods: In this study, 16 samples of a ceramic total knee arthroplasty were scanned including left and right implants (sizes 3 to 6). Each sample was left in its original packaging during scanning in order to preserve its sterile state. During the scanning procedure, two samples of the same size were scanned jointly in order to minimize scanning time. The testing was exclusively non-destructive, which poses a challenge due to the high density of zirconium (6 g/cubic centimeter). We established a non-destructive test protocol especially for ceramic knee implants in which the scanning parameters were optimized and the sample orientation was determined by CT simulations. Additionally, methods for the reduction of beam hardening artifact were applied. Results: It could be shown that a correct presentation in the micro-computer tomograph is possible despite the high density of the ceramic. In the examined specimens, no internal material defects such as pores or fractures were found. A three-dimensional examination, even of objects with a high density, can be carried out flawlessly using the micro-CT. Summary: It was shown that no pores or cracks were found in the tested implants. Non-destructive testing in micro CT is a challenging method. The highly compressed material and the complex geometry of the femoral and tibial implants make measurement difficult. Sophisticated corrective tours of the scanning artifacts and a robust scanning protocol are necessary to achieve optimal results. This study provides the prerequisites for further analysis.