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Radiophosphate uptake in asymptomatic knee arthroplasty
L Rosenthall1, L Lepanto, F Raymond
1Montreal General Hospital, McGill University, Quebec, Canada.
Summary
Radiophosphate bone scans show persistent increased uptake around total knee replacement (TKR) components, even years after surgery. This finding complicates the diagnosis of complications like loosening based on a single bone scan.
Area of Science:
- Orthopedic Surgery
- Nuclear Medicine
- Radiology
Background:
- The diagnostic accuracy of radiophosphate bone scanning for total knee replacement (TKR) complications remains unclear.
- Persistent increased radiophosphate uptake around TKR prostheses, even in asymptomatic patients, poses a diagnostic challenge.
Purpose of the Study:
- To analyze the time course of radiophosphate uptake in asymptomatic patients following TKR.
- To evaluate the utility of bone scanning in detecting TKR complications.
Main Methods:
- Retrospective analysis of bone scans from 30 asymptomatic patients with 37 TKRs.
- Scans were obtained between 1 month and 12 years post-surgery.
- Radiophosphate uptake was graded (0-4+) in femoral and tibial components.
Main Results:
- Mean femoral component uptake was significantly lower in scans obtained >1 year post-surgery (1.8) compared to ≤1 year (3.0).
- Mean tibial component uptake showed a non-significant decrease over time (3.2 vs. 2.6).
- Persistent increased uptake was noted, particularly in the tibial component.
Conclusions:
- Persistent radiophosphate uptake after TKR, especially in the tibial component, may reflect mechanical stresses rather than complications.
- Reliance on a single bone scan may be unreliable for diagnosing TKR loosening due to this persistent uptake.