Retrospective single-institution study evaluating whether a new Edema Zone classification (based on extent of femoral head edema on MRI) predicts conversion to total hip arthroplasty (THA) after core decompression for osteonecrosis of the femoral head (ONFH). Compared against the established Japanese Investigation Committee (JIC) classification.

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The Femoral Head Edema Zone: A Novel Classification Scheme to Better Predict Osteonecrosis Progression

🧠 Key Points

Study Population: 94 hips with ONFH treated with core decompression (20 converted to THA within 26 months, 74 did not).
Edema Zone vs JIC: Edema Zone classification correlated with THA conversion, while JIC did not (P < 0.001 vs P = 0.83).
Predictive accuracy: AUC 0.71 for Edema Zone vs 0.52 for JIC → better prognostic tool.
Reliability: Excellent inter-rater reliability for Edema Zone (κ = 0.87), outperforming JIC and other systems.
Risk association: Higher Edema Zone grades (≥3) had significantly greater THA conversion rates (e.g., 67% for grade 4).
Clinical implication: The Edema Zone classification provides a simple, MRI-based, reliable system to guide surgical decision-making and avoid ineffective core decompressions in high-risk patients.

The Journal of Arthroplasty (2025)

doi.org/10.1016/j.arth.2025.08.035