Avascular necrosis of the femoral head: which MRI parameters or findings are more decisive for determining the prognosis?

Background

Predicting the development of collapse in patients with avascular necrosis of the femoral head (ANFH) is critical in determining prognosis and management.

Objective

We aimed to evaluate whether MRI findings and parameters based on the Association Research Circulation Osseous (ARCO), Japanese Investigation Committee (JIC), modified Kerboul, and Mitchell classifications can predict prognosis in patients with early-stage ANFH at initial diagnosis.

Methods

This study comprises a retrospective analysis of early-stage ANFH patients without femoral head collapse. Hips with ANFH were divided into two groups based on whether they developed collapse during at least 1 year of follow-up or not. MRI findings were assessed by two radiologists and compared between the groups. Interobserver reliability was also evaluated.

Results

Patients who developed collapse had higher measurements in the percentage of midcoronal area, midsagittal area, maximum coronal area, and total necrotic area (p = 0.001, p = 0.001, p < 0.001, p = 0.003, respectively). Although all AUC values were close to each other, the percentage of maximum coronal area showed the highest AUC value (0.857; 95% CI 0.714–1.000; sensitivity 85.7%, specificity 80%) in ROC curve analysis. Interobserver reliability was best for the JIC and worst for the modified Kerboul classification (Kappa values: 0.890 and 0.492, respectively). No statistically significant difference was found among etiological factors, bone marrow edema, cyst-like changes, synovial effusion, and collapse development (p > 0.05). The double-line sign was statistically significantly more frequent in hips without collapse (p = 0.025).

Conclusion

The risk of collapse development is higher with a greater volume of necrosis in the femoral head and when the osteonecrosis is located more laterally.

Graphic abstract