目的 通过研究股骨头缺血性 坏死在坏死指数与磁共振上的分期之间 的相关性，找出坏死指数在股骨头塌陷 的临界值，从而为利用MRI图像预测股骨 头塌陷提供更可靠的参考标准(在股骨头 缺血坏死患者中，预测是否会发生股骨 头缺血坏死塌陷)。方法 分析统计我院 2012年6月至2014年2月明确诊断为股骨 头缺血性坏死且MRI检查图像可以进行明 确分期的共70例患者(共计100髋)；依照 伦诺克斯和亨格福德分期法(Lennox和 Hungerford分期法)对100个股骨头缺血 性坏死的MRI图像进行分期，另按照Koo 等提出的坏死指数法计算坏死指数，对 二者进行统计学分析，评价其相关性， 并确定股骨头塌陷的临界坏死指数值。 结果 I期至Ⅳ期股骨头缺血坏死指数分 别为(0.31±0.08)(95%CI:0.29-0.34)， (0.50±0.20)(95%CI:0.43-0.57)， (0.62±0.18)(95%CI:0.53-0.71)及 (0.83±0.23)(95%CI:0.70-0.95)。对各 期股骨头坏死指数进行显著性检验，结 果显示差异有统计学意义(P＜0.05)。以 HSD法对任意两期坏死指数进行统计学分 析，结果显示两两之间差异均有统计学 意义。Ⅱ期中有3髋坏死指数大于53%， Ⅲ期中全部坏死指数大于53%。结论 坏 死指数与股骨头缺血坏死分期期数正相 关，统计分析得到坏死指数53%可视作预 测股骨头有无塌陷风险的临界值，在临 床治疗中，坏死指数可以为预测股骨头 缺血坏死是否塌陷提供参考。

Objective To find out the critical value of necrosis index in femoral head collapse through correlation between necrosis index and magnetic resonance image (MRI) staging of ischemic necrosis of femoral head, so as to provide a more reliable reference standard for prediction of femoral head collapse with MRI (to predict whether ischemic necrotic collapse will happen in patients with ischemic necrosis and collapse of femoral head). Methods A total of 70 cases of patients (100 hips) were enrolled in this study. The patients were diagnosed as ischemic necrosis of femoral head between June 2012 and February 2014 in our hospital with MRI images that could be definitely staged. MRI images of these 100 ischemic necrotic femoral heads were staged according to LennoxHungerford staging method. And necrosis index was calculated using the method proposed by Koo et al. A statistical analysis was carried out to evaluate their correlation and to determine the critical necrosis index at femoral head collapse. Results Necrosis indexes of ischemic necrotic femoral heads at stage I to IV were (0.31±0.08)(95%CI:0.29-0.34), (0.50±0.20)(95%CI:0.43-0.57), (0.62±0.18)(95%CI:0.53-0.71) and (0.83±0.23) (95%CI:0.70-0.95), respectively. Significance test showed that the statistically significant differences between femoral heads with different stages of ischemic necrosis in necrosis indexes (P＜0.05). HSD method showed statistically significant differences between any of the two groups in necrosis index (P＜0.05). There were only 3 hips in stage II (no collapse) had necrosis index＞53%, while each hip of stage III (began to collapse) had necrosis index＞53%. Conclusion Necrosis index of ischemic necrosis of femoral head is positively associated with necrosis staging, calculated according to MRI images, necrosis index of 53% obtained in statistical analysis can be taken as critical reference to predict collapse of femoral head necrosis. In the clinical treatment, necrosis index can be used as reference for predicting whether ischemic necrotic femoral head collapses.