Introduction

Currently there are no accepted international guidelines for the correct placement of reconstruction prostheses in the axial plane of the femur after en bloc resection. The most accepted method is based on the linea aspera as an intraoperative landmark, indicating posterior. This study was conducted to address the reliability of the linea aspera as a landmark for rotational alignment.

Material and methods

50 CT angiographies of the right limb were used for this purpose. These 2D images were reconstructed into 3D models using proprietary software (materialize NV, Leuven, Belgium). The posterior condylar line was used as a reference axis. The orientation of the linea aspera was described as the angle between the perpendicular line to the PCL, through the center of the diaphysis, and the lateral (α) and medial labium (β).

Results

The linear mixed model shows that the α- and β-angles are significantly associated with the distance from the joint line (p<0.001) and vary significantly between subjects (p<0.001). The α-angle has the lowest variance and approximates more closely true posterior, while the median β-angle never overlaps true posterior.

Discussion

When a surgeon would blindly rely on the linea aspera as a posterior landmark roughly 78% of the femoral implants would exceed the accepted ±3° deviation around the surgical transepicondylar axis (sTEA) as defined in total knee replacement. The linea aspera is not a reliable landmark for axial rotation of femoral implants. The position is highly dependent on the osteotomy height and in addition differs between individual patients. Preoperative assessment of the linea aspera is advocated in order to reduce the risk of malrotation. As the height of the osteotomy cannot always be determined correctly preoperatively, a table was designed as a guideline for how much a deviation from the planned resection height will affect the rotation of the implant.

中文翻译：

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肉瘤切除后增强股骨远端假体的旋转放置。

介绍

目前，对于整块切除后在股骨的轴平面正确放置重建假体尚无公认的国际准则。最被接受的方法是基于曲霉线作为术中标志物，指示后路。进行这项研究的目的是解决细麻线作为旋转对准的标志的可靠性。

材料与方法

为此目的，使用了50条右肢CT血管造影。使用专有软件（Material NV，比利时鲁汶）将这些2D图像重建为3D模型。后con线用作参考轴。曲细线的方向被描述为与PCL垂直的线（通过骨干的中心）与外侧（α）和内侧唇（β）之间的夹角。

结果

线性混合模型显示，α和β角与距关节线的距离显着相关（p <0.001），并且在受试者之间显着变化（p <0.001）。α角具有最低的方差，并且更接近真实的后验，而中值β角从不重叠真实的后验。

讨论区

当外科医生盲目地依赖细线虫作为后标志物时，大约78％的股骨植入物将超过围绕全膝关节置换术定义的围绕手术跨ep轴（sTEA）的±3°偏差。曲骨线不是股骨植入物轴向旋转的可靠标志。位置高度取决于截骨高度，并且各个患者之间的位置也有所不同。提倡对曲霉菌进行术前评估，以减少发生旋转不良的风险。由于不能总是在术前正确确定切骨术的高度，因此设计了一个表格作为与计划切除高度的偏差会影响植入物旋转的准则。