三种内固定物固定骨盆后环损伤的生物力学研究及有限元分析

Posterior pelvic ring injuries, including sacral fracture and sacroiliac joint dislocation, remain challenges for orthopedic surgeons. Iliosacral(IS) screw fixation and posterior tension band plate(TBP) technique are two treatment alternatives for posterior pelvic ring injuries. However, IS screw fixation is lack of reduction ability and requires high technical skilles and continuous fluoroscopic guidance for appropriate screw insertion. TBP technique also has some disadvantages, including limited reduction potential, difficulty in precontouring the plate and a higher rate of symptomatic implants. To address these limitations, we introduced a minimally-invasive adjustable plate (MIAP), which obtained the patents of invention. The MIAP conforms to the irregular shape of posterior pelvic ring and can be used without prebending. This plate has a role in reducing fractures/dislocations of posterior pelvic ring. This project intends to produce transforaminal sacral vertical fractures and unilatreal sacroiliac dislocation on cadevaric pelvic specimens. These pelvic specimens will be fixed with IS screws, TBPs and MIAPs, respectively. The strain gauge and grating displacement transducer were used to test the stability and properties of force conduction of pelvic specimens under both single and circulating loads. We will also apply finite element analysis techniques to establish a normal bony pelvis-ligament model. The finite element model of pelvis with sacral vertical fracture and unilateral sacroiliac joint dislocation will be created, on which the IS screw, TBP and MIAP will be added, respectively. The stress and strain distribution of the above-mentioned models are assessed under both vertical and torsional loads. Taking into consideration the biomichanical studies of cadaveric specimens and finite element analysis, the IS screw, TBP and MIAP are compared in the ability of stabilizing posterior pelvic injuries and restoring its biomechanical properties. This study will provide biomechanical evidence to select best fixation technique for posterior pelvic ring injuries.

骶骨骨折和骶髂关节脱位等骨盆后环损伤的治疗仍是骨科医师面临的重点与难点。针对常用的经皮骶髂螺钉内固定技术要求高、医患双方X线暴露量大和张力带接骨板术中需预弯等缺点，以及两者均无复位作用的局限性，我们根据骨盆后环解剖特点及骶髂复合体生物力学特性，设计了具有复位作用的微创可调式接骨板（获得发明专利）。本课题拟制作经骶孔的骶骨纵行骨折和骶髂关节脱位模型，分别应用骶髂螺钉、张力带接骨板和微创可调式接骨板固定，应用应变片和光栅尺位移传感器考察骨盆标本在单次和循环负荷作用下的稳定性和骨盆的力学传导特性。本课题拟采用有限元分析技术，建立正常骨盆-韧带有限元模型以及骶骨纵行骨折/骶髂关节脱位应用上述三种内固定物固定的有限元模型，考量其在垂直负荷和扭转负荷下的应力应变分布,与生物力学试验相补充，比较三种内固定物固定骨盆的稳定性以及恢复其生物力学特性的情况，为骨盆后环损伤选择最佳固定方式提供生物力学依据。

骨盆骨折是临床常见的损伤，占成人骨折的3.64%，多由高能量创伤，如交通事故、高空坠落所致。其中，68.3%的骨盆骨折为不稳定骨折，是较为复杂、严重的创伤，死亡率高达19%，选择合适的治疗方法仍是骨科医师面临的重点和难点。骨盆的稳定性主要依赖于骨盆后环的完整性，因此，治疗的目的就是最大程度的恢复骨盆后环的连续性及稳定性。不稳定型骨盆骨折的治疗包括保守治疗和手术治疗。保守治疗常常会出现骨折不愈合、畸形愈合、疼痛等长期并发症。近年来，学者们建议行手术治疗不稳定型骨盆骨折。虽然外固定支架具有切口小、手术简便等优点，但是其却无法提供坚强的固定、容易导致感染和松动。内固定可以实现坚强的固定。临床常用的内固定器械有：骶髂螺钉、骶骨棒、张力带接骨板、三角固定系统等。然而，它们都有各自的局限性。为了克服上述内固定器械的不足，本课题组根据骨盆后环的解剖形态研制了可调式微创接骨板，用于治疗不稳定型骨盆骨折。本课题通过制作经骶孔的骶骨纵行骨折和骶髂关节脱位模型，分别应用骶髂螺钉、张力带接骨板和微创可调式接骨板固定，应用应变片和光栅尺位移传感器考察骨盆标本在垂直负荷作用下的稳定性和骨盆的力学传导特性。本课题采用三维有限元分析技术，建立正常骨盆-韧带有限元模型以及骶骨纵行骨折/骶髂关节脱位应用上述三种内固定物固定的有限元模型，考量其在垂直负荷下的应力应变分布,与生物力学试验相补充，比较三种内固定物固定骨盆的稳定性以及恢复其生物力学特性的情况，为骨盆后环损伤选择最佳固定方式提供生物力学依据。生物力学实验结果提示在不同垂直负荷下，2枚骶髂螺钉和可调式微创接骨板固定骨盆后环的垂直位移和分离移位无明显差别，均明显小于张力带接骨板固定骨盆后环的移位值。三维有限元分析结果提示：两枚骶髂螺钉固定的骨盆稳定性大于可调式微创接骨板固定的骨盆稳定性，更大于张力带接骨板固定的骨盆模型的稳定性。通过实验研究证实，可调式微创接骨板固定不稳定骨盆骨折时，其稳定性与使用2枚骶髂螺钉效果相似，均优于使用张力带接骨板。