Non-Destructive Testing of Ceramic Knee Implants Using Micro-Computed Tomography

Abstract

Background: Because of the accumulated numbers and the increasing rate of knee replacement surgeries larger numbers of revision cases are likely. Although the success rate of knee arthroplasties is high, complications like the loosening of the implant necessitate subsequent treatments. Therefore, new concepts such as metal-free ceramic implants are necessary, for example, using zirconium dioxide (ZrO₂). Several studies showed that the strength of ceramic ZrO₂ implants is equivalent to cobalt-chromium components.

Methods: Non-destructive testing remains challenging due to the high density (6 g/cm³) of ZrO₂. In this feasibility study, we investigated 8 tibial and 8 femoral implants respectively using an industrial X-ray micro-computed tomography (XCT) system at a voxel size of 100 μm. We established a non-destructive testing protocol for ceramic knee implants optimizing scanning parameters and sample orientation using CT simulations. Finally, we used an iterative artifact reduction procedure for beam hardening correction.

Results: The results show that corrected image data enable the non-destructive inspection of high-density components. In this sample, none of the investigated components show any internal defects like pores or cracks. In general, XCT is a major imaging method that is able to provide a 3-dimensional representation of higher dense objects that allows the inspection of metal or ceramic knee implants. Even though we established an optimized scanning routine for tibial and femoral ceramic components, it is not possible to completely eliminate scanning artifacts of XCT.

Conclusion: Altogether, after visual inspection, none of the beam-hardening corrected XCT data sets for femoral and tibial implants showed any defects, that is, no inclusions, cracks, or pores were detected. XCT test is therefore an essential addition to the fatigue testing since it is the only non-destroying testing method.

Keywords: burst; ceramic; femur; non-destructive testing; strength; tibia.