基于三维重建模拟S_1椎弓根螺钉的最佳置钉参数

Best screw placement parameters in S_1 pedicle based on three-dimensional reconstruction

背景:S1椎弓根螺钉的置入广泛应用于脊柱疾病的治疗。因骶骨本身并没有典型的椎弓根和侧块,定义骶骨横突与椎体间的过渡区为椎弓根;骶椎椎弓根内的骨质密度明显低于胸腰椎椎弓根;但S1椎体通常作为脊柱椎弓螺钉的终末椎体,承受极大的应力,临床随访中出现松动、断裂钉的并发症较多;因此对于S1椎体的置钉需个体化、精准化,以求获得最佳的生物力学。目的:通过数字化技术重建骨盆环结构模拟S1椎弓根置钉,为临床治疗提供解剖学参考。方法:选取自贡市第四人民医院2017年4至8月行骨盆CT薄层扫描的患者影像资料,排除骶椎及两侧髂骨存在外伤、骨病、先天性畸形、严重退变等情况,共获得108例成人骨盆薄层CT扫描数据。利用Mimics软件进行三维模型重建,数字化模拟最佳的空间位置置钉;以S1椎上关节突外侧缘与下缘交接处为进钉点,朝指向骶岬方向置钉。测量螺钉长度、螺钉的空间位置、螺钉钉帽与髂骨翼的相切距离、置钉平面髂骨翼之间的距离。结果与结论:(1)S1椎弓根螺钉的左侧内倾角男性为(20.73±8.04)°,女性为(24.73±8.16)°,男女左侧内倾角相比较差异有显著性意义(P=0.013);(2)右侧内倾角男性为(21.57±9.68)°,女性为(26.75±7.78)°,男女右侧内倾角比较差异有显著性意义(P=0.003);(3)左侧螺帽与髂骨翼的相切距离男性为(2.20±4.33) mm,女性为(8.03±8.81) mm,男女左侧螺帽与髂骨翼相切的距离比较差异有显著性意义(P=0.000);(4)右侧螺帽与髂骨翼的相切距离男性为(2.13±3.93) mm,女性为(7.57±6.70) mm,男女右侧螺帽与髂骨翼的相切距离比较差异有显著性意义(P=0.000);(5)男性螺钉置入平面髂骨翼之间的距离为(76.96±9.47)mm,女性为(86.52±12.56) mm,男女置钉平面髂骨翼之间的距离相比较差异有显著性意义(P=0.000);(6)男女左右侧螺钉置入的水平夹角及螺钉置入长度相比较无显著性意义(P> 0.05);(7)3例重建模型因髂骨翼阻挡不能垂直及前内侧置钉;(8)结果详细描述了川南地区人群骶椎及骨盆环的解剖特点,其S1椎弓根螺钉的置入参数可作为临床应用的参考。

BACKGROUND:Placement of S1 pedicle screw is widely used in the treatment of spinal diseases.Because the sacrum itself does not have typical pedicle and lateral block,the transitional area between sacral transverse process and vertebra is defined as pedicle.The bone density of S1 pedicle is significantly lower than that of pedicle of thoracic and lumbar vertebrae.However,the S1 vertebra is usually the end vertebra of the spine arch screw,which suffers great stress,and there are many complications of loose and broken nail in clinical follow-up.Therefore,the fixation of the S1 vertebrae needs to be individualized and precise to obtain the best biomechanics.OBJECTIVE:To reconstruct the pelvic ring structure by digital technology to simulate S1 pedicle screw placement,so as to provide anatomical reference for clinical practice.METHODS:Pelvic CT data of 108 patients in Zigong Fourth People’s Hospital between April and August,2017 obtained by CT thin slice scanning were included after excluding congenital malformation,and severe degeneration of the sacral and bilateral iliac bones.Three-dimensional model was reconstructed using Mimics software and optimal space nail was simulated by digital technology.S1 screw entry point was set as the intersection of lines where extension of S1 facet joint inferior margin and lateral margin cross over.The length of the screw,screw position,tangent distance screw nail cap and the iliac wing and the distance between plane wing of ilium nail were measured.RESULTS AND CONCLUSION:(1)The left oblique angle(α)of S1 pedicle screws was(20.73±8.04)°in males,and(24.73±8.16)°in females(P=0.013).(2)The rightαwas(21.57±9.68)°in males and(26.75+7.78)°in females(P=0.003).(3)The distance between the left screw nail cap and the iliac wing(a)was(2.20±4.33)mm in males,and(8.03±8.81)mm in females(P=0.000).(4)The right a was(2.13±3.93)mm in males,and(7.57±6.70)mm in females(P=0.000).(5)The distance between planar iliac bone(b)of screw was(76.96±9.47)mm in males,and(86.52±12.56)mm in females(P=0.000).(6)There was no significant difference in the angle(β)of the left and right sides and the length(d)of screw implantation in females and males(P>0.05).(7)Three patients could not receive vertical and medial anterior internal fixation due to iliac wing obstruction.(8)These results indicate that the anatomy of the sacral and pelvic rings in South Sichuan is described in detail.The parameters of the S1 pedicle screw implantation can be used as a reference for clinical application.