Orphanet Journal of Rare Diseases | Assessment of vascular status in femoral head cartilage in early Legg-Calvé-Perthes disease

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This study utilized contrast-enhanced magnetic resonance imaging (MRI) to systematically evaluate the vascular status of the femoral head (FH) cartilage in Stage I Waldenström-staged Legg-Calvé-Perthes disease (LCPD) patients for the first time, comparing the affected side with the contralateral normal structure. It was found that the medial and lateral regions of the FH cartilage showed significantly increased and thickened vasculature, suggesting early vascular remodeling in these areas and providing imaging evidence for early revascularization. Additionally, this study optimized MRI assessment methods for FH vasculature, offering new insights for early diagnosis and prognosis evaluation in LCPD.

 

Literature Summary
The article titled 'Femoral head vascular status in early-stage Legg–Calvé–Perthes disease assessed by contrast-enhanced magnetic resonance imaging: comparison with the contralateral side', published in the Orphanet Journal of Rare Diseases, reviews and summarizes the vascular changes in femoral head (FH) cartilage during the early stages of Legg-Calvé-Perthes disease (LCPD). The study assessed vasculature in 23 Stage I Waldenström LCPD patients using contrast-enhanced MRI and found that vascular proliferation and thickening in the FH cartilage region were primarily concentrated in the medial and lateral portions, while the capital femoral epiphysis vasculature was only visible in 7 patients. It was also found that the vascular distribution pattern in the FH cartilage region resembled that of the contralateral side, suggesting that these vessels may not be newly formed but rather part of the original vascular structure. The study emphasizes the importance of FH cartilage vascular assessment in the early stages of LCPD, providing new imaging evidence for understanding the revascularization mechanisms of the disease.

Background Knowledge
Legg-Calvé-Perthes disease (LCPD) is a childhood idiopathic avascular necrosis of the femoral head, with its pathological process closely related to the disruption of FH blood supply. Although the exact etiology of LCPD remains unclear, revascularization is considered a crucial factor in disease progression and prognosis. Previous studies mainly assessed FH revascularization through bone scans, dynamic contrast-enhanced MRI, or perfusion MRI, but these methods failed to directly visualize the cartilage vasculature. In children, FH vascular supply must pass through the cartilage; therefore, vascular changes in the cartilage may precede osseous changes and represent an early indicator of revascularization. This study fills a research gap by using precise MRI scanning protocols to divide the FH cartilage into four quadrants and comparing vascular proliferation and thickening between the affected and contralateral sides. Moreover, clinical staging of LCPD (e.g., Waldenström staging) is primarily based on X-ray imaging, while MRI is more sensitive in detecting changes in cartilage and blood supply. This study provides new imaging markers for early diagnosis and prognosis evaluation in LCPD, holding significant clinical research value.

 

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Research Methods and Experiments
The study retrospectively analyzed data from 23 patients with unilateral LCPD between January 2017 and September 2024, all in Stage I Waldenström staging and underwent contrast-enhanced MRI. Axial contrast-enhanced MRI images were used to divide the FH cartilage into four quadrants: medial, lateral, anterior, and posterior. Vascular proliferation in each quadrant was assessed by counting enhancement signals, and vessel thickening was determined by measuring vessel width. Evaluation criteria were defined as follows: if the number of vessels on the affected side exceeded 50% of the contralateral side, it was classified as 'increased'; less than 50% as 'decreased'; and between these as 'comparable'. Inter- and intra-observer comparisons were conducted using Fisher's exact test with Bonferroni correction, and consistency was assessed using intraclass correlation coefficients (ICC).

Key Findings and Observations

• In Stage I LCPD patients, the number of vessels in the FH cartilage area was significantly increased, especially in the lateral (78.2%) and medial (65.2%) regions.
• The proportions of thickened vessels in the lateral and medial FH cartilage regions were 78.2% and 60.8%, respectively, significantly higher than those in the anterior (8.6%) and posterior (26.0%) regions.
• The vascular distribution pattern in the FH cartilage was similar between the affected and contralateral sides, suggesting that the observed vessels were not newly formed but rather part of the original structure.
• Vasculature in the capital femoral epiphysis was only visible in 7 patients, indicating that revascularization in early LCPD primarily occurs in the cartilage region.
• The study also found that vascular increase and thickening in FH cartilage were not entirely consistent, suggesting heterogeneous vascular responses in different regions.
• The method demonstrated high intra- and inter-observer consistency (ICC of 0.79 and 0.74, respectively), making it suitable for clinical imaging assessment.

Research Implications and Future Directions
This study is the first systematic evaluation of vascular status in the FH cartilage region in Stage I LCPD patients, providing imaging evidence for early revascularization in LCPD. The findings suggest that cartilage vascular proliferation may occur earlier than osseous changes, indicating potential diagnostic value of MRI-based FH vascular assessment in early LCPD. Future studies with larger sample sizes and multi-center designs are needed to validate these findings and further explore the relationship between FH vascular status and clinical prognosis.

 

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Conclusion
Legg-Calvé-Perthes disease (LCPD) is a childhood disorder characterized by idiopathic avascular necrosis of the femoral head. Early diagnosis and assessment of blood supply restoration are crucial for prognosis. This study evaluated FH cartilage vascular status in Stage I LCPD patients using contrast-enhanced MRI and found a significant increase in both number and thickness of vessels in the medial and lateral FH cartilage regions. The findings suggest that vascular remodeling in FH cartilage may begin at an early stage of LCPD, offering new perspectives for early diagnosis and prognosis evaluation. Although treatment for LCPD mainly relies on physical therapy or osteotomy rather than direct vascular intervention, this study highlights the importance of MRI in assessing cartilage vascular changes. Future studies should expand the sample size and combine various imaging markers with clinical staging to further validate the correlation between FH cartilage vascular status and disease progression. Moreover, this study provides clinical references for vascular assessment in animal models of LCPD, which can enhance the targeting and efficiency of experimental design. In summary, FH cartilage vascular assessment may serve as an important imaging marker for monitoring early revascularization in LCPD, holding significant research and clinical translational potential.

 

Shiyu Huang, Xiang Cheng, Sijie Gao, Chuan Feng, and Yuxi Su. Femoral head vascular status in early-stage Legg–Calvé–Perthes disease assessed by contrast-enhanced magnetic resonance imaging: comparison with the contralateral side. Orphanet Journal of Rare Diseases.