ASTM F2978-20

5.1 Magnetic resonance imaging is ideally suited to image MOM hip arthroplasty due to its superior soft tissue contrast, multiplanar capabilities and lack of ionizing radiation. MR imaging is the most accurate imaging modality for the assessment of peri-prosthetic osteolysis and wear-induced synovitis (5.2 Before scanning a patient with a specific implant, the MR practitioner shall confirm that the device is MR Conditional and that the scan protocol to be used satisfies the conditions for safe scanning for the specific implant.

5.3 This guide can be used to identify the following adverse events.

5.3.2 Component Loosening—While the data are preliminary, MR imaging can identify circumferential bone resorption that may indicate component loosening. Loosening may result from osteolysis, circumferential fibrous membrane formation or poor osseous integration of a non-cemented component. On MR imaging, component loosening typically manifests as circumferential increased signal intensity at the metallic-bone or cement-bone interface on fat-suppressed techniques (20). The finding of circumferential fibrous membrane formation or osteolysis also indicates potential loosening; this is in contrast to a well-fixed component, with high signal intensity fatty marrow directly opposed to the implant interface.

5.3.3 Wear-Induced Synovitis—Magnetic resonance imaging is the most useful imaging modality to assess the intracapsular burden of wear-induced synovitis surrounding MOM arthroplasty (FIG. 5 Axial (left) and Coronal (right) FSE Images of a Left MOM Hip Arthroplasty

5.3.4 Infection—In the setting of infection, the synovium often demonstrates a hyperintense, lamellated appearance with adjacent extracapsular soft tissue edema. These appearances help to distinguish the synovial pattern of infection from wear-induced synovitis, although aspiration is still required for definitive diagnosis (FIG. 6 Axial FSE (left) and Inversion Recovery (right) Images of a Right MOM Hip Athroplasty

5.3.5 Adverse Local Tissue Response—Adverse local tissue reactions can manifest as synovitis, bursitis, osteolysis and cystic or solid masses adjacent to the arthroplasty, which may be termed pseudotumors (FIG. 7 Axial FSE Image in a Right MOM Hip Arthroplasty

5.3.6 Modular Taper Associated ALTR—MRI can accurately describe ALTR attributed to tribocorrosion in modular femoral neck total hip arthroplasty. MRI characteristics, particularly maximal synovial thickness and synovitis volume, can predict histologic severity (Note 1: Modular taper ALTR may occur in non-metal-on-metal implants as well as in metal-on-metal arthroplasty.

1.1 This guide describes the recommended protocol for magnetic resonance imaging (MRI) studies of patients implanted with metal-on-metal (MOM) devices to determine if the periprosthetic tissues are likely to be associated with an adverse local tissue reaction (ALTR). Before scanning a patient with a specific implant, the MR practitioner shall confirm that the device is MR Conditional and that the scan protocol to be used satisfies the conditions for safe scanning for the specific implant. This guide assumes that the MRI protocol will be applied to MOM devices while they are implanted inside the body. It is also expected that standardized MRI safety measures will be followed during the performance of this scan protocol.

1.2 This guide covers the clinical evaluation of the tissues surrounding MOM hip replacement devices in patients using MRI. This guide is applicable to both total and resurfacing MOM hip systems.

1.3 The protocol contained in this guide applies to whole body magnetic resonance equipment, as defined in section 201.3.239 of IEC 60601-2-33, Ed. 3.2, with a whole body radiofrequency (RF) transmit coil as defined in section 201.3.240. The RF coil should have circulary polarized RF excitation (also commonly referred to as quadrature excitation) as defined in section 201.3.249 of IEC 60601-2-33, Ed. 3.2..

1.4 The values stated in SI units are to be regarded as standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. The user may consider all precautions and warnings provided in the MR system and hip implant labeling prior to determining the applicability of these protocols.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.