骶髂螺钉置入S1椎弓根的形态学研究

目的研究S1椎弓根的形态学特点，探讨经骶髂关节置入S1椎弓根螺钉的可行性。方法测量16具尸体骨盆标本双侧S1椎弓根前后缘的高度、深度(S1椎弓根最狭窄处的宽度)、骶翼深度、骶翼高度。测量骨盆出口位X线片上S1椎弓根的高度，并与肉眼解剖比较。在轴位CT图像上测量髂骨后缘到骶翼、S1椎弓根、S1椎弓根纵轴的距离、髂骨外板与骶椎前缘皮质的距离。观察S1椎弓根矢状切面，评估置入2枚经S1椎弓根骶髂螺钉的安全区。结果椎弓根前后缘的高度平均为30．2mm、26．Imm，椎弓根深度和骶翼深度平均为27．8mm、45．8mm，骶翼后部平均高度为28．7mm。骨盆出口位X线片上S1椎弓根的平均高度是20mm，小于肉眼解剖测量结果(P＜0．0001)。轴位CT图像上，S1椎弓根纵轴在髂骨外板投影点到髂骨后缘的距离平均为32．5mm，到坐骨大切迹最高点的距离平均为38．6mm，髂骨外板到S1椎体前缘皮质的距离平均为105．2mm。结论置入1枚S1椎弓根螺钉是安全的，常规置入2枚椎弓根螺钉可能较困难。

Morphologic study on the first sacral vertebral pedicle for the placement of sacroiliac screw

Objective To investigate the morphologic characteristic of the pedicle of the first sacral vertebra (S₁); to discuss the feasibility of inserting screws to the pedicle of S₁ through sacroiliac joint. Methods Anterior and posterior height, depth, alar depth, and posterior alar height of the pedicle of S₁ were measured on 16 cadaveric pelves bilaterally. Sacral pedicle height was also measured on the out-let X-ray as visualized during intraoperative fluoroscopy,and compared with actual anatomic pedicle height. The distance from the posterior limit of the ilium to the sacral ala, pedicle of S₁ and its axis, and the distance between the outer table of the ilium and anterior cortex of the sacrum were measured on axial computed tomography scans. Finally parasagittal sections of the pedicle of S₁ were observed to assess the safety zone for inserting two pedicle screws into the vertebral body. Results The mean height of the anterior and posterior pedicle was 30.2 mm and 26.1 mm respectively. The mean depth of the pedicle and ala was 27.8 mm and 45.8 mm respectively. The mean posterior alar height was 28.7 mm.The mean pedicle height of S₁ was 20 mm measured on the out-let X-ray, which was significantly less(P<0.0001)than the actual anatomic pedicle height. The mean distance from the posterior limit of the ilium to the projection point on the outer table of the ilium of pedicle axis on axial computed tomography scans was 32.5 mm, and the mean distance from this point to the top of the greater sciatic notch was 38.6 mm.The mean distance between the outer table of the ilium and the anterior cortex of the sacrum was 105.2 mm.Conclusion The placement of one sacral pedicle screw into the vertebral body is safer, and routine placement of two sacral pedicle screws may be difficult.