采用三维有限元方法分析股骨颈动力交叉钉系统（FNS）与空心拉力螺钉对Pauwels Ⅲ型股骨颈骨折治疗稳定型的影响。

选择1名25岁健康男性志愿者，既往身体健康，X线检查未见髋关节发育异常，行髋关节CT薄层扫描，收集其股骨中上段影像学数据，并将其导入到医学三维重建软件Mimics 19.0中，得到原始股骨三维模型；并在Geomagic Wrap 2017软件中进行逆向优化，同时构建股骨皮质骨与松质骨结构；后导入至Solidworks 2017软件中建立Pauwels Ⅲ型股骨颈骨折三维模型；同时使用Solidworks2017软件，按照临床中内固定尺寸建立FNS模型及空心拉力螺钉模型，同时建立其与PauwelsⅢ型股骨颈骨折的组合模型，从而建立股骨颈骨折4种治疗模型（模型1：FNS主钉临床标准点位植入模型；模型2：FNS主钉偏斜于标准点植入模型；模型3: 3枚倒三角平行空心拉力螺钉植入模型；模型4: 2枚平行空心拉力螺钉植入模型）；最后在ANSYS17.0软件中进行网格划分、施加载荷和数据计算，分析各模型股骨与内固定的应力分布、应力峰值、最大位移及下肢外旋应力下位移情况，每个三维有限元模型在相应区域范围内均匀采点20个，记录每个位点的相应数值。

（1) 4种内固定模型在不同压力下股骨颈骨折远近端应力值模型1最大，但骨折端应力差值最小，其次为模型3；（2) 4种内固定模型在不同压力下股骨近端应力模型1最小；（3) 4种内固定模型中的模型1与模型2内固定应力明显较其余两种高；（4) 4种内固定模型中不同压力股骨颈轴线（X轴）位移及水平（Z轴）位移随压力增加位移大，模型1最小，其次为模型3；（5) 4种内固定模型中的股骨颈矢状位（Y轴）位移模型3最小，其次为模型1；（6) 4种模型在下肢外旋应力下，股骨颈矢状位（Y轴）位移模型1与3较其余两种小。

FNS标准植入治疗股骨颈骨折表现出优秀的支撑、抗内翻、抗旋转及抗外旋应力作用，3枚倒三角平行空心拉力螺钉同样表现出优秀的支撑、抗内翻、抗旋转及抗外旋应力作用，其支撑及抗内翻应力作用较股骨颈动力交叉钉系统略差。同时发现，不合理的股骨颈动力交叉钉植入位置，对其治疗股骨颈骨折稳定性影响较大，能明显降低其抗旋转及抗外旋能力。

Three dimensional finite element method was used to analyze the effect of FNS and CCS on the stability of Pauwels Ⅲ femoral neck fracture.

A 25-year-old healthy male volunteer who X-ray examination showed no abnormal hip development was selected to undergo Hip CT thin layer scan and collect the imaging data of the middle and upper segment of femur, then his data were imported into the medical 3D reconstruction software Mimics 19.0 to obtain the original 3D model of femur and performed in Geomagic Wrap 2017 software to simultaneously construct the cortical bone and cancellous bone structure of the femur. Then it was imported into Solidworks 2017 software to establish the three dimensional model of Pauwels Ⅲ femoral neck fracture. At the same time, using the Solidworks 2017 software to establish the FNS model and the hollow lag screw model according to the clinical internal fixation size, and the combination model with Pauwels Ⅲ type femoral neck fracture was established, so as to establish four treatment models for femoral neck fracture (model 1: clinical standard spot implantation model of FNS nail. Model 2: FNS main nail implantation model deviated from the standard point; Model 3: Three inverted triangle parallel hollow lag screw implantation model. Model 4:2 parallel hollow lag screw implantation model). Finally, ANSYS17.0 software was used to perform mesh division, load application and data calculation. Stress distribution, stress peak value, maximum displacement and displacement under external rotational stress of femur and internal fixation of each model were analyzed. 20 points were uniformly selected in each three dimensional finite element model within the corresponding region, and corresponding values of each site were recorded.

(1) In the 4 models under different pressures, the stress value of proximal and distal end of femoral neck fracture was the largest in Model 1, but the stress difference of fracture end was the smallest, followed by Model 3. (2) In the 4 models, the proximal femur stress of model 1 was the smallest under different pressures of different internal fixation models. (3) In the 4 models,the internal fixation stress of model 1 and Model 2 is obviously higher than that of the other two models. (4) In the 4 models, the axial (X-axis) and horizontal (z-axis) displacements of femoral neck under different pressures in different internal fixation models were larger with the increase of pressure, and the model 1 was the smallest, followed by Model 3. (5) In the 4 models, femoral neck sagittal (Y-axis) displacement model 3 was the smallest, followed by model 1. (6) In the 4 models, under the external rotational stress of lower limbs, the sagittal (Y-axis) displacement of femoral neck model 1 and 3 were smaller than the other two models.

Standard implant therapy of femoral neck fracture with FNS showed excellent support, varus resistance, resistance to rotation and extorsion stress resistance, three nabla parallel hollow tension screw also showed a good support, varus resistance, resistance to rotation and extorsion stress resistance, in its support and resistance to stress the femoral neck slightly less power cross nail system. At the same time, it was found that the improper placement of FNS had a great influence on the stability of the treatment of femoral neck fracture, and significantly reduced the anti-rotation and anti-external rotation ability of the screw.