骶骨骨折的动态冲击试验研究

Experimental study of the sacrum fracture under the dynamics clashing load

目的:探讨骶骨在冲击载荷作用下发生骨折的机理。方法:采集人体新鲜骨盆标本10具,分别行动态冲击试验和静态破坏试验,测量动态骨折时的一系列动力学参数,确定骨折的动力学特性。结果:⑴骶骨受垂直冲击时按应力波的传递方向发生骨折,其动力学性质呈粘弹性,应力波呈周期性衰减,得到了骶骨的载荷响应曲线与应变响应曲线;骶骨骨折的平均冲击载荷为(9366±514) N,冲击时间为(2.78±1.02) s,动荷系数为1.21。⑵骶骨的动态破坏机制与静态破坏机制有很大的不同,不但极限载荷不同,而且前者随应变速率的提高而快速增加,冲击能量在25 J以上时呈脆性劈裂状通过骶孔或骶髂关节骨折,并累及神经根损伤,而静态大多为骶髂关节骨折。结论:骶骨骨折大都在高速冲击下发生,与其动力学特性、力的传导以及动载荷响应等诸多因素相关。

Objective: To discuss the mechanism how the sacrum fracture happens under the dynamics clashing load. Methods: 10 fresh pelvis specimen were collected and carried out the clash test in dynamic state and the destruction test in static state individually, while measured parameters of the fracture in dynamics state for making sure the dynamic parameter of fracture. Results: (1) Fracture happened in the direction of stress wave when the sacrum was clashed,its dynamics property had a feature of viscoelasticity,and the stress wave presented periodically attenuation. We can get the curve of responds in the load and strain. The average clashing pressure was 9366±514 N, the clashing time 2.78±1.02 s, and the coefficient of dynamic stress 1.21. (2)Both the mechanism of dynamic destruction and static destruction of pelvis had a significant difference. That is to say, not only the limit pressure, but also the pressure in dynamic state was different, which increased rapidly with the strain rate. When the clash energy was beyond 25 J, the sacrum fracture belonged to typeⅡin general, or fracture of sacroiliac accompanying with the injury of nerve root. Fracture of sacroiliac in static state was iliosacral articulation mostly. Conclusions: The sacrum fracture is a kind of dynamic injury and mostly happens in the situation of high-speed clashing,it is relevant to the characteristics of dynamics, the conduction of strength, the stress and the strain of the sacrum.