摘要
目的 建立疲劳试验模型 ,初步观察脊柱内固定器经疲劳试验后刚度变化。方法 圆柱状钢质夹具 ,固定脊柱标本 ,两侧焊有平衡杆 ,用于加载的上端夹具底部制做偏心状轴承 ,在平衡杆上固定弹簧装置模仿脊柱后方骶棘肌。选取 1 0具新鲜脊柱标本截取L1 -S2节段 ,制备L3椎体损伤模型。按临床手术方法分别安装复位固定系统 (ReductionFixtion ,RF)和改良Edwards系统 (ModifiedEdwardsSystem ,MES)。在SANS材料试验机上 ,以频率 0 5Hz载荷 ( 44 0± 1 65 )N对标本进行 1 0 0 0 0次循环加载。观察初始状态、1 5 0 0次和 1 0 0 0 0次循环后两组刚度变化及固定节段下位椎间盘位移变化。结果 疲劳前RF和MES组刚度增加 ,经 1 5 0 0次和 1 0 0 0 0次循环后RF组仍保持着良好的刚度 ,MES组刚度减弱 ,RF组刚度明显高于MES组 (P <0 0 5 ) ;疲劳前后两组固定节段下位椎间盘位移与完整状态相比无明显变化 (P >0 0 5 )。结论 本实验制作的疲劳模型适用于脊柱内固定器的生物力学测试。
Objective To establish the fatigue test device and observe the stiffness of two spinal posterior fixation devices in the fatigue test. Methods The testing apparatus consisted of two round plate which fixed specimens. The pivot of upper plate, which was fixed balance rods, was made of a 3 cm anterior offset to the specimens. To simulate the effect of erector spinae muscle force on the spinal segment, a sping was mounted between the two rods posterior the specimens. In ten specimens using lumbosacral cadaveric spine(L1-S2), with an L3 burst fracture, two dorsally applied spinal fixation implants(Reduction Fixtion,RF and Modified Edwards System,MES)were used acording to clinical operation. In SANS testing machine, the specimens were loaded cyclically at 0.5Hz in(440±165)N for up to 10,000 cycles. Displacement transducers monitored motion at the site of instability and at the segment below the implants. Flexibility at these segments were measured at initial and 1500 and 10000 cycles. Results In the fracture models, a one-way analysis of variance showed that there were more significant differences in flexibility of the two fixation constructs(P<0.05). The stiffness of RF and MES was increased at initial cycles. RF allowed significantly more rigid across the site of instability than MES at 1500 and 10000 cycles. There were no significantly more stiffness between the fixation constructs and intact spine at the segment below the implants. Conclusion This fatigue test device is fit for biomechanical study of spinal interal instrumentation.
出处
《医用生物力学》
EI
CAS
CSCD
2002年第2期115-118,共4页
Journal of Medical Biomechanics
