髋臼上区域置钉安全范围的影像学研究

目的　探究髋臼上区域螺钉的进钉位置、角度以及安全范围。 方法　收集男女骨盆CT数据各50例，利用Mimics软件重建髋臼上置钉区域三维模型（髂前下棘至髂后上棘方向）。同一横断面上，通道狭窄处中点连线方向确定为螺钉方向，沿该方向每2.5 mm为一层，逐层测量安全范围相关指标。在1/2高度层面放置中心钉，测量中心钉进钉点与髂前下棘的位置关系及螺钉方向，在水平面和矢状面上移动钉尖，测量安全倾角范围。 结果　髋臼上骨通道存在前、后两狭窄点，不同层面其宽度不同，从下至上，前狭窄由窄变宽再变窄，后狭窄逐层增宽。螺钉通道中间层较宽，上下层较窄；中心通道宽度90%的男、女性分别大于7 mm和6 mm；进钉约50 mm至前狭窄，70 mm至坐骨大切迹顶上方，100 mm至后狭窄，全程长约130 mm；螺钉为内倾、头倾方向，与矢状面和横断面的夹角均约为30°；97%的进钉点位于髂前下棘中心外侧，其中外下方占71%。 结论　髋臼上螺钉的进钉点主要位于髂前下棘外方，内倾、头倾方向，与矢状面和横断面的夹角均约为30°。

A primary imaging study on quantitative measurement of the supra-acetabular screw safe fixation zone

Objective　To investigate the entry point location and orientation of the supra-acetabular screw as well as its safe corridor size. Methods 100 (male 50, female 50) CT data of pelvis were collected from our hospital. The three-dimensional model of supra-acetabular corridor (oriented from the anterior inferior iliac spine (AIIS) to posterior superior iliac spine (PSIS) was reconstructed by Mimics software. On the horizontal scan, the screw was placed along the two midpoints of the anterior and posterior narrowing in the corridor, and the relevant parameters of safe corridor were measured from inferior to superior at an interval layer thickness of 2.5 mm. On the middle layer, the orientations of the central virtual screws were measured and the position relation between the entry point and the center apex of AIIS was determined. The safe fixation zone was measured by moving the tip of the screw on the horizontal and sagittal planes. Results　There were two narrowing in the supra-acetabular corridor. From inferior to superior, the width of the anterior narrowing had the characteristic of narrow-wide-narrow and the posterior narrowing became wider and wider. The width for safe fixation corridor from inferior to superior had the feature of narrow-wide-narrow. The width of the corridor on the middle layer was (10.61±2.10) mm for male and (8.44±2.03) mm for female (t=7.413，P<0.001). On the middle layer, the distances from the entry point to anterior narrowing, greater sciatic notch and posterior narrowing were about 50 mm, 70 mm and 100 mm, respectively. The whole length of the corridor was about 130 mm. The inward inclination angle was (29.50±4.05) degrees for male and (28.00±3.78) degrees for female (t=2.709, P=0.007), and the virtual screw had a safe rang about 5 degrees. The cranial inclination angle was (29.40±5.38) degrees for male and (28.57±6.01) degrees for female (t=1.025, P=0.306), and the safe rang was about 10 degrees. 97% of the entry points were located on the lateral area of the AIIS, and 71% in the lateral-inferior quadrant. Conclusion The entry point of the supra-acetabular screw are located on the lateral area of the AIIS. The inward and cranial inclination angles are both about 30 degrees.