Correlation of Necrotic Index and Modified Necrotic Index With the Harris Hip Score and Their Reliability in Patients With Osteonecrosis of the Femoral Head

Both indices showed significant negative correlations with HHS. The modified necrotic index demonstrated a strong correlation (r = -0.940, p < 0.001), whereas the original necrotic index exhibited a moderate correlation (r = -0.790, p < 0.001). The interclass correlation coefficient (ICC) for assessment of lesion size was significant for both indices (p < 0.05), but it was higher for the modified index (ICC = 0.81) compared to the original index (ICC = 0.69). Levene's test for homogeneity of variance indicated unequal variance across the two methods (p < 0.01). Measurement variance was smaller for the modified index than for the original index (p < 0.01), indicating greater precision. Both methods showed significant interobserver and intraobserver agreement (p < 0.05) Conclusion: Both the necrotic index and the modified necrotic index showed significant negative correlations with HHS. The modified necrotic index demonstrated a strong correlation, whereas the original necrotic index exhibited a moderate correlation. Both methods proved reliable for measuring lesion size, with the modified method showing greater precision. Additionally, both indices demonstrated significant interobserver and intraobserver reliability.