Using the percentage of necrotic surface area to predict collapse of avascular necrosis of the femoral head / 中华骨科杂志

ABSTRACT

Objective To explore the value of the percentage of necrotic surface area in predicting collapse of osteonecrosis. Methods 15 hips of avascular necrosis of the femoral head(ANFH) in 9 patients underwent MRI scan. On the MRI films, the percentage of necrotic surface area were calculated. While on the specimens of the 15 hips, the percentage of necrotic surface area were also measured. In 16 hips of 8 patients of ANFH with serials MRI at mean 18.9 months intervals (range, 6-41 months), the percentage of necrotic surface area were calculated and compared. In 38 hips of 27 patients without collapse, the percentage of necrotic surface area and the index of necrosis were calculated on MRI films. Follow-up was terminated when crescentic sign illustrated on X-ray film or CT demonstrated articular facet collapse. Those hips without collapse were followed up more than 24 months. The value of the percentag of necrotic surface area and the index of necrosis in predicting collapse of osteonecrosis was observed. Results The percentage of necrotic surface area were 63.23%?10.16% on specimens and 63.60%?7.78% on MRI films respectively. There were no significant differences between them. The percentage of necrotic surface area on specimens were coincidence with those on MRI. In the 16 hips with serials MRI; the percentage of necrotic surface area were 52.37%?19.91% on the first MRI films, 51.70%?21.29% on the second. There were no significant differences between them. This result revealed that the percentage of necrotic surface area did not vary with the extension of course of disease. In the 38 cases of early necrosis, 28(73.7%) hips collapsed and 10(26.3%) hips did not. The relative risk of the percentage of necrotic surface area was 1.043, and the relative risk of the index of necrosis was 1.020. No significant difference was found in ARCO staging for patients with or without femoral head collapse. It demonstrated that whether ischemic necrotic femoral head collapse or not had no relation with its ARCO stage. Conclusion The percentage of necrotic surface area can be used as more accurate predictor for future collapse.