S2横形螺钉固定变异骶骨Ⅲ区骨折的影像解剖学研究

S2 transverse screw fixation of zone Ⅲ fracture of dysmorphic sacra: an anatomical and image study

目的探讨S_1椎不能横形置入骶髂螺钉固定骶骨Ⅲ区骨折时,置入S_2横形螺钉的安全参数。方法用Mimics软件对96例骨盆CT数据进行三维重建,模拟横形置入S_1、S_2螺钉,根据能否横形置入S_1螺钉将骶骨病例分为正常组与变异组。重建骨盆周围软组织,确定S_2横形螺钉进钉点B、髂前上棘顶点M、髂嵴上点N的体表投影点B_1、M_1、N_1,并测量各点间的长度。结果正常组男、女B_1M_1长度分别为(140.94±16.64)mm、(143.95±16.27)mm,均明显大于变异组男、女B_1M_1的长度(129.37±14.93)mm、(132.07±16.84)mm(P_男<0.05,P_女<0.05)。正常组与变异组B_1N_1的长度男性分别为(69.92±6.73)mm、(72.64±7.46)mm,女性分别为(60.80±7.05)mm、(58.85±7.81)mm,其差异均无统计学意义(P_男>0.05,P_女>0.05)。正常组与变异组M_1N_1的长度男性分别为(157.58±16.83)mm、(150.48±13.21)mm,女性分别为(156.79±15.84)mm、(151.49±16.58)mm,其差异均无统计学意义(P男>0.05,P女>0.05)。结论当S_1椎为腰骶移行椎、高位骶骨或骶骨翼斜坡陡峭变异时不能横形置入骶髂螺钉,可经S_2横形置入直径7.0 mm螺钉固定骶骨Ⅲ区骨折,术者在透视监视下可通过触摸髂前上棘及髂嵴来确定S_2螺钉的体表进钉点。

Objective To investigate the safety parameters of S2 transverse screw when the sacroiliac screw cannot be transversely placed into the first sacral（S1） vertebra to fix zone Ⅲ sacral fractures.Methods The 3-D models of 96 pelvis were reconstructed by Mimics software based on CT data, and the virtual S1 transverse sacroiliac screws were placed. When the transverse sacroiliac screw cannot be safely inserted in S1, it would be regarded as a dysplasia. There were 34 S1 vertebrae which belonged to the dysplasia group, and the other paired 34 S1 vertebrae according to gender were classified to the normal group.Placement of the S2 transverse sacroiliac screws were simulated in 68 S2 vertebrae, and then the parameters of screw paths were measured respectively. The soft tissues on pelvic surface were generated by Mimics, and then the body surface projections of S2 transverse screw＇s entry point B, anterior superior iliac spine＇s vertex M, iliac crest point N were determined as B1, M1, N1, respectively. At the same time, the lengths of B1M1, B1N1 and M1N1were measured in section. Results There was significant difference in the lengths of the line B1M1, which were（140.94 ± 16.64） mm and（129.37 ± 14.93） mm in male between the normal group and the dysplasia group（P〈0.05）, and the lengths of the line B1M1were（143.95±16.27） mm and（132.07±16.84） mm in female with statistical difference between the normal group and the dysplasia group（P〈0.05）. The lengths of the line B1N1 in the normal group and the dysplasia group were（69.92±6.73） mm and（72.64±7.46） mm in male with no statistical difference（P〉0.05）, and were（60.80±7.05） mm and（58.85±7.81） mm in female with no statistical difference（P〉0.05）. The lengths of the line M1N1were（157.58±16.83） mm and（150.48±13.21）mm in male of the normal group and dysplasia group, which showed no statistical difference（P〉0.05）.Similarly, there was no significant difference in the lengths of the line M1N1, which were（156.79±15.84） mm and（151.49 ± 16.59） mm in female between the two groups（P〉0.05）. Conclusion When the sacroiliac screw cannot be transversely placed in dysplasia S1 vertebra including lumbosacral transitional vertebrae,sacrum not recessed in pelvis andacute alar slope. A 7.0 mm sacroiliac screw can be inserted in S2 vertebra for fixing zone Ⅲ sacral fractures. Under fluoroscopic monitoring, the body surface entry point of S2 screw can be determined by touching the bony landmarks of the anterior superior iliac spine andiliac crest.