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目的:探讨后路枕骨髁螺钉安全置入的钉道参数范围，并评估最佳的进钉点。方法:回顾性分析2016年9月至2018年9月接受上颈椎CTA扫描64例患者的数据，排除骨折脱位、肿瘤及椎动脉水平段变异等。利用Mimics软件对枕骨、寰椎及椎动脉进行三维重建，以枕骨髁后方内、外侧中点及中点水平方向左、右侧间隔3 mm分别为中、内侧、外侧3个候选进钉点，测量各进钉点枕骨距椎动脉水平段上缘的垂直距离（vertebral artery-occipital distance，VOD），定义VOD> 4 mm可容纳直径3.5 mm螺钉置入。将直径3.5 mm的虚拟螺钉分别以最大头倾角及最小头倾角结合各进钉点下最长钉道的合适内倾角置入VOD>4 mm的进钉点，随后将置钉后的三维模型导入3-Matic软件中测量置钉参数，计算各进钉点头倾角安全范围及置钉成功率，并进行统计学分析。结果:内侧、中进钉点VOD分别为（8.07±2.13）mm、（7.70±2.19）mm，对应的可容纳置钉率分别为97.7%、96.1%，中、内侧进钉点VOD及可容纳置钉率的差异均无统计学意义；而外进钉点VOD为（5.63±1.66）mm，可容纳置钉率仅78.9%，均明显低于内侧、中进钉点，差异均有统计学意义。外侧进钉点可获得相对较大的内倾角度（44.14°±4.06°），从而辅以较长的钉道长度[（24.22±1.82）mm]；而中、内侧进钉点的内倾角度及钉道长度随着进钉点的内移逐渐减小，分别为中进钉点[31.27°±3.85°，（21.82±1.66）mm]、内侧进钉点[24.37°±3.32°，（19.49±1.62）mm]；外侧、中、内侧进钉点的数据差异有统计学意义。中、内侧进钉点的头倾角安全范围分别为2.32°~21.43°（12.58°±4.23°）和3.41°~20.81°（12.09°±3.83°），差异无统计学意义；而外侧进钉点的头倾角安全范围仅2.07°~15.24°（8.17°±2.55°），明显小于中、内侧进钉点，差异有统计学意义。在可容纳螺钉置入的进钉点中，外、中进钉点辅以5°头倾角可获得最大的置钉成功率，分别为98.02%与98.37%，而内进钉点在3°头倾角下可获得100%的置钉成功率。结论:后路枕骨髁螺钉在水平方向进钉点的选择中，中、内侧进钉点受椎动脉水平段影响较小，具有较高的置钉成功率及较大的头倾角安全范围，而内侧进钉点的螺钉置入长度不及中、外侧进钉点，因此中进钉点作为后路枕骨髁螺钉的最佳进钉选择更显合适。“,”Objective:To investigate the safety and feasibility of the occipital condyle screw and evaluate the safepath parameters for the occipital condyle screw.Methods:Data of 64 patients with upper cervical computed tomographic angiograms from September 2016 to September 2018 were retrospectively collected. Excluded occipito-cervical injury, tumor, and vertebral artery course variation. Mimics software was used to reconstruct the occiput, atlas and vertebral artery. Three candidate entry points were placed for each occipital condyle, the midpoint of posterior of occipital condyle as middle entry point, and the medial and lateral entry points were located 3 mm medial and lateral to the middle entry point. The vertebral artery-occipital bone distance (VOD) of each entry point were measured on sagittal plane, and the minimum feasible value was determined to be 4mm. After that 3.5 mm diameter virtual screw was inserted into each candidate entry point with VOD>4 mm, each screw with maximum and minimum cranial angulation was combined with appropriate medial angulation to get the maximum screw length. Then, the screw placement parameters were measured by 3-Matic, and the safe range of cranial angulation and the success rate of screw placement were calculated.Results:The VOD of medial and middle entry point were 8.07±2.13 mm and 7.70±2.19 mm respectively, and the feasibility rate of screw placement of those entry point were 97.7% and 96.1%, respectively. There were significant differences inVOD and feasibility rate of screw placement between medial and middle entry point. The VOD of lateral entry point was 5.63±1.66 mm, and the feasibility rate was only 78.9%, which was significantly lower than that of medial and middle entry point. The lateral entry point could obtain a larger medial angulation, which was supplemented by a longer screw length. The medial angulation and length of screw gradually decreased with the inward movement of the entry point. There were significant differences in medial angulation and screw length among groups. The safe range of cranial angulation of medial, middle and lateral entry points were 8.17°±2.55°, 12.58°±4.23° and 12.09°±3.83°, respectively, and the difference were statistically significant. Among the screw entry point that could accommodate screw fixation, the maximum screw placement success rate can be obtained by adding 5° cranial angulation to the lateral and middle entry point, which were 98.02% and 98.37%, respectively,while 100% success rate of screw placement could be obtained at the medial entry point at 3° cranial angulation.Conclusion:In the selection of the entry point in the horizontal direction, middle and medial entry points have higher success rate of screw placement and wider safe range of cranial angulation because of less affection of horizontal segment of the vertebral artery. However, the screw length of medial entry point is much shorter than middle and lateral entry point. As a result, the middle entry point may be an optimal entry point for the occipital condyle screw.