Magnetic Resonance Safety Evaluation of a Novel Alumina Matrix Composite Ceramic Knee and Image Artifact Comparison to a Metal Knee Implant of Analogous Design

Abstract

Background: Image artifacts caused by metal knee implants in 1.5T and 3T magnetic resonance imaging (MRI) systems complicate imaging-based diagnosis of the peri-implant region after total knee arthroplasty. Alternatively, metal-free knee prostheses could effectively minimize MRI safety hazards and offer the potential for higher quality diagnostic images.

Methods: A novel knee arthroplasty device composed of BIOLOX delta, an alumina matrix composite (AMC) ceramic, was tested in a magnetic resonance (MR) environment. American Society for Testing and Materials test methods were used for evaluating magnetically induced displacement force, magnetically induced torque, radiofrequency-induced heating, and MR image artifact.

Results: Magnetically induced displacement force and magnetically induced torque results of the AMC ceramic knee indicated that these effects do not pose a known risk in a clinical MR environment, as assessed in a 3T magnetic field. Moreover, minimal radiofrequency-induced heating of the device was observed. In addition, the AMC ceramic knee demonstrated minimal MR image artifacts (7 mm) in comparison to a cobalt-chromium knee (88 mm). The extremely low magnetic susceptibility of AMC (2 ppm) underlines that it is a nonmetallic and nonmagnetic material well suited for the manufacturing of MR Safe orthopaedic implants.

Conclusions: The AMC ceramic knee is a novel metal-free total knee arthroplasty device that can be regarded as MR Safe, as suggested by the absence of hazards from the exposure of this implant to a MR environment. The AMC ceramic knee presents the advantage of being scanned with superior imaging results in 3T MRI systems compared to alternative metal implants on the market.

Keywords: Alumina matrix composite; Ceramic; Image artifact; Knee implant; Magnetic resonance imaging; Total knee arthroplasty.

Figure 1

RF-induced temperature rises for the AMC ceramic knee after 15 minutes of scanning in a 3T MRI system, normalized to the initial temperature.

Figure 2

AMC ceramic knee with a spin echo pulse sequence in a 3T MRI system. Worst-case image (left), background image (middle), resulting image artifact (right). Measurements are in millimeters.

Figure 3

AMC ceramic knee with a gradient echo pulse sequence in a 3T MRI system. Worst-case image (left), background image (middle), resulting image artifact (right). Measurements are in millimeters.

Figure 4

CoCr knee with a spin echo pulse sequence in a 3T MRI system. Worst-case image (left), background image (middle), resulting image artifact (right). Measurements are in millimeters.

Figure 5

CoCr knee with a gradient echo pulse sequence in a 3T MRI system. Worst-case image (left), background image (middle), resulting image artifact (right). Measurements are in millimeters.

Fig. S1

Slices through the empty gel phantom of electric field in V/m (top) and SAR in W/kg (bottom) for simulated RF application in a 3T/123 MHz MRI system. Computational analysis of the gelled saline phantom showed that the left side of the gelled saline phantom is associated with a greater electrical field. Thus, the test article was positioned on the far-left side of the gelled saline phantom (not shown).

Fig. S2

Fiber Optic Thermometry Probe locations during RF-induced heating evaluation on a 3T MRI system (Discovery MR750 [GE Healthcare]). Three probes were placed on the implant. The fourth probe served as a reference and was located on the opposite side of the gel phantom.