Anderson et al reported a grading system for soft tissue changes seen adjacent to metal-on-metal (MoM) hip prostheses. The authors are from Norfolk and Norwich University Hospital and Norwich Radiology Academy in England.
Imaging: metal artefact reduction (MAR) magnetic resonance imaging (MRI)
Findings |
Interpretation |
Grade |
normal appearance with or without small seroma or small hematoma |
normal |
A |
fluid-filled cavity with high signal T2 wall OR bone marrow edema OR inflammatory changes in soft tissues |
infection |
B |
fluid-filled peri-prosthetic cavity less than 5 cm in maximum diameter OR periprosthetic soft tissue mass less than 5 cm in diameter with no hyperintense T2W fluid signal |
mild MoM |
C1 |
peri-prosthetic soft tissue mass or fluid-filled cavity >= 5 cm in diameter OR C1 lesion with additional findings (see below) |
moderate MoM |
C2 |
fluid-filled cavity extending into deep fascia OR tendon avulsion OR fracture OR intermediate T1W soft tissue cortical or marrow signal |
severe MoM |
C3 |
Additional findings for a CI lesion seen with a C2 lesion:
(1) muscle atrophy or muscle edema in any muscle other than short external rotator
(2) bone marrow edema (hyperintense on STIR)
Grade |
Management |
C1 |
continue monitoring |
C2 |
elective revision |
C3 |
urgent revision |
Specialty: Surgery, orthopedic
ICD-10: ,