骶骨Denis Ⅲ区骨折经皮横形骶髂螺钉固定的影像解剖学研究

Percutaneous transverse sacroiliac screw fixation of Denis Ⅲ sacral fracture:an anatomical and imaging study

目的:通过对骶髂关节三维重建模型进行解剖参数测量和虚拟螺钉固定,明确骶骨Ⅲ区骨折横形骶髂螺钉固定的安全进针点和置入角度。方法:用Mimics(materialise’s interactive medical image control system,Mimics)软件对50例骨盆薄层CT进行三维重建,切割出骨盆三维模型,并对S1椎体进行解剖参数测量,然后模拟置钉,确定横形螺钉的进针点和安全角度。应用Mimics软件重建骨盆表面软组织,确定进钉点Q、髂前上棘顶点M、髂嵴上点N的体表投影点Q_0、M_0、N_0,分段测量各投影点间的长度。结果:髂前上棘顶点连线QM的长度男性为(101.60±6.60)mm,女性为(102.00±7.75)mm,两者无统计学意义(P>0.05);过点Q作QM的垂线与髂嵴交于点N,QN的长度男性为(58.68±6.93)mm,明显大于女性的(47.89±6.62)mm;点M沿髂嵴到点N的长度男性为(134.25±8.84)mm,女性为(133.47±8.53)mm,两者之间的差异无统计学意义(P>0.05)。体表投影Q_0M_0在男性的长度为(120.96±14.11)mm,女性为(128.74±14.18)mm,其差异无统计学意义(P>0.05);男性Q_0N_0的长度为(55.29±9.96)mm,明显大于女性的(46.09±5.75)mm。所有中心螺钉前后倾均值为(0.93±3.24)°,头尾倾均值(0.38±2.58)°。S1椎体变异率为31.51%,骶骨变异率在男女间的差异无统计学意义(P>0.05)。结论:术前在体表确定髂前上棘顶点M_0和髂嵴上点N_0后可明确骶骨Ⅲ区骨折横形螺钉的体表进钉点,术中在C臂机透视下以S1椎体上表面为水平面、后表面为冠状面,螺钉垂直于矢状面,无头尾倾和前后倾可安全拧入。术前需行骨盆CT及三维重建明确S1椎体有无变异以确定能否拧入横形螺钉。

Objective：To identify transverse sacroiliac screw＇s safety entry point and angle for fixation of Denis Ⅲ sacral fracture by anatomical parameter measurement of S1 vertebra and virtual screws fixation of the three-dimensional reconstruction model of the sacroiliac（SI）joint. Methods：The three-dimensional models of pelvis were reconstructed and cut by Mimics software based on 50 pelvises CT data. The anatomical parameters of S1 vertebra were measured and the four virtual transverse SI screws were placed in each pelvis,then the central transverse SI screw＇s entry point and angles were identified. The soft tissues on pelvic surface were reconstructed by Mimics software,then the surface projection of the screw＇s entry point Q,anterior superior iliac spine＇s vertex M,iliac crest point N were determined as Q0,M0,N0,respectively. At the same time,the lengths of Q0M0,Q0N0 and M0N0were measured sectionally. Results：The lengths between center screw＇s entry point Q and anterior superior iliac spine＇s vertex M were（101.60±6.60）mm in male and（102.00±7.75）mm in female without statistical difference between two groups（P〈0.05）. Point N was intersecting point between iliac crest and the line QN,which was vertical line of QM passing the entry point Q,then the lengths of QN were（58.68 ±6.93） mm in male and（47.89 ±6. 62） mm in female with statistical difference between two groups（P〈0.05）. The lengths of the line MN from anterior superior iliac spine＇s vertex M to point N,which was along the iliac crest,were（134.25±8.84）mm in male and（133.47±8.53）mm in female with no statistical difference between two groups（P〈0.05）. The lengths between Q0 and M0were（120.96±14.11）mm in male and（128.74±14.18）mm in female,and the difference between two groups is no statistical significance（P〈0.05）,the lengths between Q0 and N0were（55.29±9.96）mm in male and（46.09±5.75）mm in female with statistical difference between two groups（P〈0.05）. The average angle of all the center screws in the forward and backward inclination was（0.93±3.24）°,and the average angle in the cephalic and caudal inclination was（0.38±2.58）°. The variation rate of S1 vertebra was 31.51%,and there is no statistical difference between male and female（P〈0.05）. Conclusion：After the anterior superior iliac spine＇s vertex M0 and iliac crest point N0 in body surface are identified in preoperative,the transverse screw＇s entry point for fixation of Denis Ⅲ sacral fracture can be determined. In C-arm monitor,when the superior surface of S1 vertebra is defined as horizontal plane and the posterior surface as coronal plane,the transverse screw can be placed safely,which is perpendicular to the sagittal plane with no forward-backward and cephalic-caudal inclination. The preoperative pelvic CT and 3- D reconstruction is strongly recommended before the transverse screw is inserted in bilateral SI joints because of high variation of S1 vertebra.