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Imaging-Based Diagnosis and Radiographs–MRI Correlation
Why This Matters
- Most common late cause of revision after total knee arthroplasty (TKA)
- A critical diagnosis in postoperative knee imaging
- Core principle:
Radiographs diagnose loosening.
MRI characterizes the biological response and extent.
Radiographic Findings — Primary Diagnostic Tool
Aseptic loosening is still, first and foremost, a radiographic diagnosis.
Key Radiographic Signs
- Periprosthetic radiolucency > 2 mm
- Component migration
- Stem–cortex contact
MRI Findings — Pathophysiologic Correlation
MRI does not replace radiographs, but adds critical diagnostic confidence.
Typical MRI Features
- Periprosthetic bone marrow edema–like signal
- Best appreciated on T1-weighted images for interface localization
Important Negative Findings
- No thin fibrous membrane
- No uniform low-signal interface line
- Helps differentiate loosening from other postoperative interface changes
Synovial and Joint Findings
- Joint effusion with villous / frond-like synovial proliferation
- Synovium shows low-to-intermediate signal intensity
- Consistent with wear-debris–related aseptic synovitis
- Not suggestive of infection
Advanced Imaging — When Needed
- CT with metal artifact reduction
- SPECT/CT
Key Take-Home Points
- Radiographs make the diagnosis
- MRI explains the mechanism
- Always exclude infection first, but imaging patterns can strongly favor aseptic loosening
#DrSlothic #SlothicRadiology #MSKRadiology
#AsepticLoosening #TotalKneeArthroplasty
#PostoperativeImaging #KneeMRI
#RevisionArthroplasty #OrthopedicRadiology
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