Inoue Shinji, Akagi Masao, Asada Shigeki, Mori Shigeshi, Zaima Hironori, Hashida Masahiko
Department of Orthopaedic Surgery, Kindai University Hospital, Osaka-Sayama City, Osaka, Japan.
Department of Design and Development, Kyocera Medical Corporation, Osaka City, Osaka, Japan.
J Arthroplasty. 2016 Sep;31(9):2025-30. doi: 10.1016/j.arth.2016.02.043. Epub 2016 Feb 27.
Medial tibial condylar fractures (MTCFs) are a rare but serious complication after unicompartmental knee arthroplasty. Although some surgical pitfalls have been reported for MTCFs, it is not clear whether the varus/valgus tibial inclination contributes to the risk of MTCFs.
We constructed a 3-dimensional finite elemental method model of the tibia with a medial component and assessed stress concentrations by changing the inclination from 6° varus to 6° valgus. Subsequently, we repeated the same procedure adding extended sagittal bone cuts of 2° and 10° in the posterior tibial cortex. Furthermore, we calculated the bone volume that supported the tibial component, which is considered to affect stress distribution in the medial tibial condyle.
Stress concentrations were observed on the medial tibial metaphyseal cortices and on the anterior and posterior tibial cortices in the corner of cut surfaces in all models; moreover, the maximum principal stresses on the posterior cortex were larger than those on the anterior cortex. The extended sagittal bone cuts in the posterior tibial cortex increased the stresses further at these 3 sites. In the models with a 10° extended sagittal bone cut, the maximum principal stress on the posterior cortex increased as the tibial inclination changed from 6° varus to 6° valgus. The bone volume decreased as the inclination changed from varus to valgus.
In this finite element method, the risk of MTCFs increases with increasing valgus inclination of the tibial component and with increased extension of the sagittal cut in the posterior tibial cortex.
胫骨内侧髁骨折（MTCFs）是单髁膝关节置换术后一种罕见但严重的并发症。尽管已有一些关于MTCFs手术陷阱的报道，但尚不清楚胫骨内翻/外翻倾斜度是否会增加MTCFs的风险。
我们构建了一个带有内侧组件的胫骨三维有限元模型，并通过将倾斜度从6°内翻改变为6°外翻来评估应力集中情况。随后，我们在胫骨后皮质添加2°和10°的矢状骨延长切口后重复相同步骤。此外，我们计算了支撑胫骨组件的骨体积，其被认为会影响胫骨内侧髁的应力分布。
在所有模型中，均在胫骨内侧干骺端皮质以及切割面拐角处的胫骨前、后皮质观察到应力集中；此外，后皮质上的最大主应力大于前皮质上的最大主应力。胫骨后皮质的矢状骨延长切口在这三个部位进一步增加了应力。在矢状骨延长切口为10°的模型中，随着胫骨倾斜度从6°内翻变为6°外翻，后皮质上的最大主应力增加。随着倾斜度从内翻变为外翻，骨体积减小。
在这种有限元方法中，MTCFs的风险随着胫骨组件外翻倾斜度的增加以及胫骨后皮质矢状切口延长的增加而增加。
