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Prognosis value of early diffusion MRI in Legg Perthes Calvé disease
C Baunin1, D Sanmartin-Viron1, F Accadbled2
1Department of Paediatric Imaging, hôpital des Enfants, CHU de Toulouse, 31059 Toulouse, France.
Insights
Diffusion MRI can predict Legg Calvé Perthes disease prognosis. An apparent diffusion coefficient (ADC) ratio of the femoral metaphysis above 1.63 indicates a poor outcome, offering early insights before traditional methods.
Area of Science:
- Orthopedic imaging
- Pediatric radiology
- Biomedical engineering
Background:
- Legg Calvé Perthes (LCP) disease affects the proximal femoral epiphysis in children.
- Accurate prognosis is crucial for effective treatment planning.
- Current prognostic indicators may have limitations in early stages.
Purpose of the Study:
- To assess the utility of diffusion MRI in predicting the prognosis of LCP disease.
- To evaluate the apparent diffusion coefficient (ADC) of the proximal femoral epiphysis and metaphysis.
- To correlate ADC measurements with established prognostic classifications.
Main Methods:
- Prospective study of 31 children with unilateral LCP disease.
- MRI scans performed during condensation or fragmentation stages.
- Bilateral measurement of ADC in femoral epiphysis and metaphysis, calculating ADC ratios.
- Comparison of ADC ratios with Herring classification.
Main Results:
- Increased ADC in affected hips compared to unaffected sides (epiphysis P<0.001, metaphysis P<0.0001).
- Femoral metaphysis ADC ratio > 1.63 correlated with poor prognosis (Herring B-C or C) with 89% sensitivity and 58% specificity.
- Excellent interobserver reliability for ADC measurements.
- The 1.63 threshold was identifiable as early as the condensation stage.
Conclusions:
- Diffusion MRI is a non-invasive, non-radiating imaging technique.
- ADC ratio of the femoral metaphysis shows promise as an early prognostic factor for LCP disease.
- This method may offer prognostic information prior to the applicability of Herring classification.
Purpose:
To evaluate diffusion MRI of the proximal femoral epiphysis and metaphysis as a prognosis factor in Legg Calvé Perthes (LCP) disease.
Methods:
Thirty-one children (mean age 5.5 years, range 2.5-10.5) with unilateral LCP were included in a prospective, consecutive series. Radiographs were analysed and classified as per Herring criteriae. Mean follow-up was 19 months (range 6-30). Forty-nine MRI scans were performed at either the condensation or fragmentation stage. Apparent Diffusion Coefficient (ADC) of both the femoral epiphysis and metaphysis were measured bilaterally and ADC ratio were calculated, then compared to the Herring group.
Results:
Sixteen hips were rated Herring A or B, 3 Herring B-C and 12 Herring C. ADC was increased in affected hips compared to unaffected sides, both at the femoral epiphysis (P<0.001) and metaphysis (P<0.0001). ADC ratio of the femoral metaphysis was positively correlated to Herring classification: if superior to 1.63, it was associated with a bad prognosis (Herring B-C or C) (P=0.0017, sensitivity=89%, specificity=58%). Interobserver reliability of ADC measurement was excellent. The 1.63 threshold could be determined as early as the condensation stage.
Conclusions:
Diffusion presents several advantages including being non radiating and non invasive. It does not need contrast medium administration and it can be performed without anaesthesia. The origin of the increased ADC remains unknown. Basically, it reflects molecular changes (true diffusion) but it is also influenced by the vascular supply (pseudo-diffusion). ADC ratio could provide an early prognosis before Herring classification is applicable.
Level Of Evidence:
Level III. Prospective uncontrolled study.
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