髋臼后柱后区的解剖学和影像学研究

Anatomy and radiology of the back zone of acetabular posterior column

目的 探讨髋臼后柱后区的解剖学和影像学特点及其对后柱拉力螺钉固定的指导意义. 方法 收集10例（20侧）正常成年男性患者（年龄为24 ～ 67岁,平均36.1岁）的骨盆核磁共振轴位片,在坐骨棘尖平面（P1）和坐骨棘尖上5 mm平面（P2）用线1～5模拟三方位（髋臼正位、闭孔斜位和髂骨斜位）透视.线2和线3分别与后柱后骨面交于A、B点,线1与线2、线3分别交于D、C点.E为CD中点,过E作CD的垂线与后柱后面交于F点.在P1、P2平面上测量AD长度（a1、a2）和EF长度（b1、b2）,以及坐骨神经前缘至后柱后骨面的距离（L1、L2）.统计坐骨神经与四边形“ABCD”的位置关系. 结果 “ABCD”盲区参数：a1=（11.62±2.29） mm,b1=（9.24±1.64） mm;a2=（13.63±1.85） mm,b2=（9.01±1.94） mm.坐骨神经前缘至后柱后骨面的距离：L1 =（7.42±1.90） mm,L2=（5.83±1.93） mm.在P1平面,坐骨神经位于“盲区”内的比例为85％,其中R1区内40％,R1/R2交界区内为45％;而仅有15％位于“盲区”外.在P2平面,85％的坐骨神经位于R1区内,也仅有15％位于“盲区”外. 结论 髋臼后柱后侧面骨性结构不规则,且坐骨神经紧邻后柱骨面,是坐骨神经被拉力螺钉损伤的解剖学基础.仅依靠三方位透视不足以评估后柱拉力螺钉的位置,增加后柱切线位透视或导航有助于螺钉的准确置入.

Objective To characterize the clinical anatomy and radiology of the acetabular posterior column and to explore their significance for lag screw fixation of the acetabular posterior column.Methods This study was carried out on the axial magnetic resonance imaging of 20 right and left pelves of 10 adult males,aged from 24 to 67 years （mean,36.1 years）.The parameters were measured on the plane of the ischial spine apex （P1） and the plane 5 millimeters above P1 （P2）.Five lines were drawn to simulate the fluoroscopy at the anteroposterior,iliac oblique and obturator oblique views.Line 2 and line 3 intersected the posterior aspect of the posterior column at points A and B,respectively.Line 1 intersected line 2 and line 3 at points D and C,respectively.Point E was the midpoint of CD.EF was perpendicular to CD,and intersected the posterior aspect of the posterior column at point F.On P1 and P2,the lengths of AD （a1,a2） and EF （b1,b2） and the shortest distance between the front edge of the sciatic nerve and the posterior column were measured （L1,L2）.Last,the position of the sciatic nerve relative to the quadrilateral “ABCD” was surveyed.Results The shape of the “shadow area” is akin to a right-angled trapezoid.The parameters of the “shadow area” are as follows：a1 =11.62 ±2.29 mm,b1 =9.24 ± 1.64 mm,a2 =13.63 ± 1.85 mm,b2 =9.01 ± 1.94 mm.The distances between the nerve and the posterior column are as follows：L1 =7.42 ± 1.90 mm,and L2 =5.83 ± 1.93 mm.On P1,85% of the sciatic nerve is in the “shadow area” （40% in R1 and 45% in the junctional zone of R1 and R2） and just 15% is out of the “shadow area”.On P2,85% of the sciatic nerve is in the R1 region and just 15% is out of the “shadow area”.Conclusions Since bony structure of the acetabular posterior column is irregular and the distance between the sciatic nerve and the posterior column is very limited,it is likely that the sciatic nerve may be injured by a lag screw.As it is not enough to define positions of a lag screw by 3 fluoroscopic views,tangential view of the posterior column or navigation technology can help implant a lag screw accurately.