骶骨不同水平切除对骨盆稳定性影响的生物力学研究

The study of biomechanicai stability of pelvis after sacrectomy

目的研究正常骶骨的力学特性和选择性骶骨切除后对骨盆力学结构产生的生物力学效应，探讨骶骨部分切除后重建的必要性。方法采用6具成人防腐骨盆标本，于试验器具内固定双侧坐骨结节模拟坐姿，通过WE-5电子万能试验机分级加载0、200、400、600、800、1000N，在骨盆上沿着主应力迹线方向布置电阻应变片，分别测量并记录骨盆完整时、经S3、S2、S1神经孔上下缘横行切除骶骨时、切除一侧骶髂关节时骨盆的主要应力传导路径和应力分布、应力应变关系、位移趋势及刚度变化，测量并记录经S1神经孔上缘切除后残余骶骨结构的极限载荷。结果骶骨主要应力分布于S1上方，经S1神经孔上缘平面切除应力传导方向发生改变，局部应力集中发生突变，其轴向刚度和弯曲刚度严重削弱，旋转和轴向稳定性差，骶骨承重能力下降明显（P〈0．05）。其极限载荷接近或低于站立前屈下生理载荷，有骨折的危险。结论S1神经孔以上骶骨是应力传导的最重要结构，切除达S1神经孔上缘平面以上结构损害了骶骨正常生理承载能力，骶骨次全切除或全切除术后应行内固定重建以恢复生理性应力传导。

Objective To study the hiomechanical characteristics of normal sacrum, the effect of selective sacrectomy on pelvis stability, and to explore the necessity of reconstruction with internal fixation instruments after sacrectomy. Mothods Six human cadaveric pelvis were placed on WE-5 omnipotent machine, which mimicked setting posture. Compressive stress was loaded on the specimens. The resistors were placed along main stress line of the pelvis. The main stress conducting pathway, stress distribution, stressstrain relation, displacement and the change of rigidity of the pelvis were analyzed on the unresected sacrum, on the sacrum resected along S3, S2, S1 neural foramen, and on the pelvis with removal of one sacroiliac joint, respectively. The maximum load of remnant sacrum was measured when the specimens were resected cephalad to the S1 neural foramina. Results The stress of the sacrum was mainly distributed above the plane of foramina of S1. When the sacrum was resected cephalad to the S1 neural foramina, the direction of the stress transmission had changed and the local stress concentration had overacted. The axial and yield rigidity of the sacrum had critically weakened. The stability of axial direction and rotation had also declined. The weight hearing ability of sacrum had decreased obviously（P〈0.05）. The yield load was lower than the physiological load in anteflexion standing position, which may lead to fracture. Conclusion The construction cephalad to the S1 foramina is the most important part of mechanotransduction. The ability of physiological load hearing of sacrum is destructed when transverse partial sacrectomy is performed cephalad to the S1 neural foramina. Reconstruction with internal fixation after suhsacrectomy or total sacrectomy is necessary to maintain the physiological mechanotransduction.