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Updated: May 12, 2026
In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis
Published on: October 20, 2013
Can decreased femoral head enhancement differentiate between septic hip arthritis and transient synovitis?
Boaz Karmazyn1, Christopher L Newman2, Monica M Forbes-Amrhein2
1Department of Radiology and Imaging Sciences, Riley Hospital for Children at IU Health, Indiana University School of Medicine, 705 Riley Hospital Dr., Indianapolis, IN, 46202, USA. Bkarmazy@iu.edu.
Objective:
To determine whether decreased femoral head enhancement on MRI differentiates septic arthritis from transient synovitis.
Materials And Methods:
This retrospective study included children < 10 years old with hip effusion on post-contrast MRI for suspected musculoskeletal infection. Two pediatric radiologists independently assessed femoral head enhancement. Kocher and modified Kocher scores were calculated from clinical and lab data. Differences between septic arthritis and transient synovitis were analyzed using Student's t-tests and Fisher's exact tests. Sensitivity and specificity for diagnosing septic arthritis were calculated for Kocher scores, their individual components, decreased femoral head enhancement, and muscle edema. Interobserver agreement was assessed.
Results:
Thirty-four children were included (20 transient synovitis, 14 septic arthritis). Kocher and modified Kocher scores were significantly higher in septic arthritis (p = 0.003, 0.008). Interobserver agreement for femoral head enhancement was substantial (kappa = 0.70). On consensus read, decreased femoral head enhancement was seen in 71.4% of septic arthritis and 50.0% of transient synovitis cases (p = 0.296). Bone marrow edema was present in two septic arthritis cases. Muscle edema had moderate to high sensitivity (71.4%, 92.9%) but moderate to low specificity (75.0%, 50.0%) for septic arthritis.
Conclusion:
Decreased femoral head enhancement does not reliably distinguish septic arthritis from transient synovitis. Relying on this finding alone may lead to unnecessary interventions in children with transient synovitis. Muscle edema and bone marrow edema may support the diagnosis of septic arthritis. Clinical evaluation and inflammatory markers remain critical in guiding decisions for hip aspiration.
Insights
Decreased femoral head enhancement on MRI does not reliably differentiate septic arthritis from transient synovitis in children. Clinical evaluation and inflammatory markers are crucial for accurate diagnosis and guiding hip aspiration decisions.
Area of Science:
- Pediatric Radiology
- Musculoskeletal Imaging
- Infectious Disease Diagnosis
Background:
- Septic arthritis and transient synovitis are common causes of hip pain in children.
- Differentiating between these conditions is critical for appropriate management.
- Magnetic Resonance Imaging (MRI) is often used to evaluate hip effusions.
Purpose of the Study:
- To evaluate the diagnostic utility of decreased femoral head enhancement on MRI in distinguishing septic arthritis from transient synovitis in children.
- To compare the effectiveness of MRI findings with clinical scores and other imaging markers.
Main Methods:
- Retrospective analysis of children under 10 years old with hip effusion on post-contrast MRI.
- Independent assessment of femoral head enhancement by two pediatric radiologists.
- Calculation of Kocher and modified Kocher scores and analysis of muscle/bone marrow edema.
Main Results:
- Thirty-four children were included (14 septic arthritis, 20 transient synovitis).
- Decreased femoral head enhancement was observed in 71.4% of septic arthritis and 50.0% of transient synovitis cases (p=0.296).
- Muscle edema showed moderate to high sensitivity but moderate to low specificity for septic arthritis.
Conclusions:
- Decreased femoral head enhancement on MRI is not a reliable differentiator between septic arthritis and transient synovitis.
- Muscle and bone marrow edema may aid in diagnosing septic arthritis.
- Clinical assessment and inflammatory markers remain essential for guiding hip aspiration decisions.
