后Pilon骨折影像形态学研究

Morphological characteristics of posterior Pilon fractures:a CT based study

目的探讨后Pilon骨折在CT三维重建图像上的形态学表现。方法将踝关节X线上"双廓征"与"台阶征"作为确诊后Pilon骨折的标准。在CT横断面图像上,分别测量后外侧与后内侧骨块骨折线与双踝连线的夹角(α、β角)、骨折块前后径与胫骨远端前后径比值、骨折块面积与胫骨远端总面积比值;在CT矢状面图像上,测量骨折块最大高度及骨折线与胫骨解剖轴的夹角(γ、θ角)。结果 36例后Pilon骨折中有28例发生距骨脱位或半脱位,26例骨折线累及内踝。在影像归档和通信系统(PACS)上完成测量,α、β角正负不同,表明骨折线方向不同。后外侧、后内侧骨折块前后径与胫骨远端前后径比值存在统计学差异(P<0.05),分别为29.8%±4.6%和24.3%±5.2%;后外侧、后内侧骨折块面积与胫骨远端总面积比值无统计学差异(P=0.65);后外侧、后内侧骨折块最大高度分别为(24.6±6.2)mm与(21.9±8.4)mm,两者有统计学差异(P<0.01);后内侧骨块骨折线相对于后外侧骨块骨折线更加垂直水平面(P<0.05)。结论符合X线诊断标准的后Pilon骨折发生距骨脱位概率较高。后Pilon后内侧、后外侧骨折块在骨折线方向、前后径与胫骨远端前后径比值及最大高度方面存在一定差异。

Objective To explore the morphological characteristics of posterior Pilon fractures based on CT.Methods The cases diagnosed as posterior Pilon fractures,which were included in this retrospective study,were based on the＂double contour sign＂and＂Step-off sign＂shown on X-rays.On the transverse CT view,the cross angleαbetween the posterolateral fragments and the bimalleolar line and the angleβbetween the posteromedial fragments and the bimalleolar line,fragment length ratio（FLR）of the anteroposterior length of either posterior fragment to that of the anterior plafond,and fragment area ratio（FAR）of the area of either posterior fragment to that of the anterior plafond were measured.On the sagittal CT view,the cross angleγandθbetween the fracture lines and the tibial axis,and the maximal fragment heights（FH）of the posterior fragments were measured in the picture archiving and communication system.Results Based on the diagnosis of posterior Pilon fractures,36 cases were brought into this study.Both posterolateral and posteromedial fragments were found in these cases,among which 28 had talar subluxation or dislocation,and 26 had fracture lines extending to the medial mallelous.The FLR of posterolateral and posteromedial fragments were 29.8%±4.6% and 24.3%±5.2%,respectively;FH of them were 24.6±6.2 mm and 21.9±8.4 mm,respectively.Both parameters were found significantly different between the posterolateral and posteromedial fragments.But no significant difference was observed in the fragment area ratio between the two fragments.There were significant differences between angleαandβas well as between angleγandθ（P〈 0.01）.The statistics indicated that the direction of major fracture lines of posteromedial and posterolateral on the axial plane was different,and the sagittal fracture lines of the posteromedial fragments were more vertical than that of the posterolateral fragments.Conclusion Posterior Pilon fractures diagnosed according to the X-ray criteria had a high rate of talar subluxation.The posterolateral and posteromedial fragments were different in the fragment length,height and fracture lines.