动力性交锁髓内钉的生物力学研究

背景骨延迟愈合、交锁钉断钉是静力型带锁髓内钉的常见并发症,而抗旋转、防短缩功能差仍是动力髓内钉目前尚未完全解决的问题.目的对静力性交锁髓内钉的结构进行改良,探讨其动力交锁的性能与力学原理.设计随机对照实验研究.地点和对象实验在成都军区总医院临床实验室完成.研究对象为志愿捐献的股骨干标本.干预将标本制成为横断骨折和粉碎骨折交锁钉固定模型,将外带锁髓内钉远端的圆形锁孔改为长形锁孔,近端改为翼状,对骨折模型进行固定并做轴向压缩载荷实验和扭力实验.并根据尾翼的形状和宽度进行对比性研究.主要观察指标横断骨折和粉碎骨折模型折端的压力、锁钉承受的剪力和尾翼的最大扭矩.结果动力性固定组骨折断端加压力为(3593.4±142.0)～(5 712.3±149.3)N,静力性固定组为(2 671.9±23.9)～(2 995.2±28.1)N(P＜0.01);动力性固定消除了髓钉与锁钉间的剪力,有效防止了断钉,并消除了骨折端的应力遮挡;齿状尾翼的防旋转能力可达11.3N·m.结论改良髓内钉起到了动力固定的加压效果和静力固定的轴向稳定性作用.

Biomechanics ofdynamic intramedullary interlocking nail

BACKGROUND: Delayed union and interlocking nail broken are very common complications of treatment of femoral fracture with locked static intramedullary interlocking nails,while problems like rotation and compression are still the shortcomings of dynamic intramedullary nails.OBJECTIVE: To improve the construction of static intramedullary interlocking nails and to explore its dynamic performance and mechanics principles.DESIGN: A randomized controlled study.SETTING and PARTICIPANTS: The experiment was conducted at the Clinical Lab of Chengdu Military General Hospital with femurs donated voluntarily as the subjects.INTERVENTIONS: The models of cominuted or intersection fractures with intramedullary interlocking nail were made on the femurs. The distal round hole of the locked intramedullary nail was changed to dolichomorphic shape and the proximal part was changed to tail wing shape with self-locking devise. The axial compression,the anti-contraction function and the anti-rotation function of the tail wing were measured and the results were compared with those of static fixation.MAIN OUTCOME MEASURES: The pressure on the fractured part in intersection fractures and comminuted fractures,the shear force on the locked nail,and the maximum torque on the tail wing.RESULTS: The pressure on the fractured part was(3 593.4 ± 142.0) to (5 712.3 ± 149.3) N in dynamic fixation group,and (2 671.9 ±23.9) to (2 995.2±28. 1) N in the static fixation group (P ＜ 0.01) .Dynamic fixation prevented the nail from breaking and diminished the stress block between the fragments by eliminating the shear force between intramedullary nail and the locked nail. The torque of dentate tail wing could CONCLUSION: The improved dynamic intramedullary interlocking nail has the compression effect of dynamic fixation and maintains the axial stability of static interlocking fixation.