Grading Systme of Anderson et al for the Severity of Soft Tissue Changes Adjacent to a Metal-on-Metal Hip Prosthesis Seen on Magnetic Resonance Imaging
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
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