功能和机械性踝关节不稳腓骨和距骨位置的MRI比较

The Comparison of the Fibular and Talus Position between Patients with Functional and Mechanical Ankle Instability by MRI

目的:探讨功能性踝不稳(FAI)和机械性踝不稳(MAI)腓骨和距骨的位置差异以及一种影像学鉴别方法。方法:对65例FAI和70例MAI患者及60名健康志愿者进行研究。根据轴位MRI图像,通过踝距骨指数(MTI)确定距骨的旋转方向。以外踝相对于距骨的轴踝指数(AMI)和外踝相对于内踝的踝间指数(IMI)来评估腓骨的位移。结果:事后多重比较结果显示,MAI患者的MTI(90.01°±2.21°)明显大于FAI患者(87.73°±1.56°,P<0.001)和健康志愿者(86.79°±2.35°,P<0.001),根据MTI角度判断FAI和MAI的最佳临界点为87.86°(灵敏度81.03%,特异度91.07%),受试者操作特征(ROC)曲线下面积为0.86(P<0.001)。MAI患者的AMI(11.42°±1.53°)明显大于健康志愿者(8.12°±1.03°,P<0.001)。FAI患者与健康志愿者在上述3项指标上无显著性差异。结论:FAI患者不存在腓骨后移和距骨内旋。MAI患者的MTI明显大于FAI患者。MTI角度增加可能成为一种新的MRI间接征象,可用于FAI和MAI的鉴别。

Purpose:To evaluate the fibula and talus position in patients with functional ankle stability(FAI)or mechanical ankle stability(MAI)by using MRI,and to provide a method in identifying these two kinds of ankle instability.Methods:Sixty-fiveand seventy patients with functional and mechanical instability,and 60 healthy volunteers were involved.Based on the axial MRI images,the rotation of the talus was identified through the malleolar talus index(MTI).The position relative to the talus(axial malleolar index,AMI)and medial malleolus(intermalleolar index,IMI)were used to evaluated the displacement of the fibula.Receiver operating characteristic(ROC)curve was used to analyze the diagnostic value of MTI.The sensitivity and specificity of this method were calculated.Results:Post-hoc analysis showed that the MTI of patients with mechanical ankle instability(90.08°±2.21°)was significantly higher than that of patients with functional ankle instability(87.73°±1.56°,P<0.001)and healthy volunteers(86.79°±2.35°,P<0.001),the best cut-off value for FAI and MAI based on the MTI is 87.86°(with the sensitivity 81.03%,specificity 91.07%),and the area under the receiver operating characteristic(ROC)curve is0.86(P<0.001).The AMI of MAI(11.42°±1.53°)was significantly higher than that of healthy volunteers(8.12°±1.03°,P<0.001).There is no significant difference between FAI patients and healthy volunteers in the above three indicators.Conclusions:The functional instability patients didn’t have a posteriorly positioned fibula and an internally rotated talus.The malleolar talus index angle was significantly larger among mechanical instability patients than that in functional instability patients.Increased malleolar talus index angle may become a new indirect MRI sign for identifying functional and mechanical instability patients.