A proper reduction and internal fixation of posterior malleolar fractures can be challenging, as intraoperative fluoroscopy often underestimates the extent of the fracture. Our aim was to assess the value of a modified classification system for posterior malleolar fractures, which is based on computed tomography (CT) images, optimizing screw trajectory during fluoroscopic-guided surgery, and to compare it to the Lauge-Hansen classification system to the CT-based classification. A retrospective review of all ankle fracture operations from January 2014 to December 2016 was performed. Fractures were included if a CT scan was performed within 1 week of the surgery, and the posterior malleolar fragment occupied one third or more of the antero-posterior talar surface or jeopardize the ankle stability. Eighty-five adult ankle fractures with posterior malleolar fragments were included in this study. Fractures were categorized into one of three types, namely “postero-lateral,” “postero-medial,” or “postero-central,” according to the location of the fracture fragment on axial CT image. An optimal trajectory angle for a single-lag screw fixation was measured on the CT cut between a central antero-posterior line and the line intersecting the posterior fragment perpendicular to the major fracture line. Mean trajectory angles were calculated for each fracture type. Fractures were also categorized according to the Lauge-Hansen system. The mean trajectory angle was 21° lateral for “postero-lateral” fragments, 7° lateral for “postero-central” fragments, and 28° medial for “postero-medial” fragments (p < 0.01 for comparisons among the groups). The range of trajectory angles within each group was about 10°, as compared to about 20° within each Lauge-Hansen type. There were no differences in trajectory angle among the Lauge-Hansen groups (p > 0.05 for all comparisons). There are 3 distinct anatomic subgroups of posterior malleolar fragments, each with an ideal screw trajectory that needs to be used in order to achieve an optimal reduction and fixation.

中文翻译：

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用于优化后踝骨折内固定的术前计划和手术技术：CT与标准X射线照片

后踝骨折的适当复位和内固定可能具有挑战性，因为术中透视通常会低估骨折的程度。我们的目的是评估改良后的后踝骨折分类系统的价值，该系统基于计算机断层扫描（CT）图像，在荧光镜引导下的手术过程中优化螺钉轨迹，并将其与Lauge-Hansen分类系统进行比较。基于CT的分类。回顾性回顾了2014年1月至2016年12月的所有踝关节骨折手术。如果在手术后1周内进行了CT扫描，则包括骨折，并且后踝碎片占据了距后距骨表面的三分之一或更多，或者损害了踝关节的稳定性。这项研究包括了八十五具后踝骨折的成人踝关节骨折。根据骨折碎片在轴向CT图像上的位置，将骨折分为“后外侧”，“后内侧”或“后中央”三种类型之一。在中心前后位线和垂直于主要骨折线的后段相交线之间的CT切口上，测量单向螺钉固定的最佳轨迹角。计算每种骨折类型的平均轨迹角。骨折也根据Lauge-Hansen系统分类。“后外侧”碎片的平均轨迹角为外侧21°，“后中央”碎片的横向轨迹为7°，“后内侧”碎片的内侧轨迹为28°（组间比较，p <0.01）。每组内的轨迹角范围约为10°，而每种Lauge-Hansen型内的轨迹角范围约为20°。Lauge-Hansen组之间的轨迹角没有差异（对于所有比较，p> 0.05）。后踝碎片有3个不同的解剖亚组，每个亚组都需要使用理想的螺钉轨迹，以实现最佳的复位和固定。