静态三维钉板系统与滑动鹅头钉固定不稳定股骨颈骨折的生物力学比较

Biomechanical comparison of static three-dimensional screw-plate system and dynamic hip screw in fixing unstable femoral neck fracture

目的:对静态三维钉板系统进行生物力学比较,评价静态三维钉板系统的力学性能。方法:于2004-01/02在国防科技大学航空与航天材料学院进行力学实验。将11付成人股骨标本(苏州医学院解剖教研室提供)随机数字法分为两大组。骨折模型组(8付)和完整骨组(3付)。骨折模型组制备伴后部粉碎、Pauwels角70°的股骨颈大角度剪切骨折模型,再随机分为抗扭实验组(4付)和抗压实验组(4付),双侧分别以静态三维钉板系统或滑动鹅头钉固定,进行抗扭和抗压实验;完整骨组以同前固定后再取出,行破坏性抗压实验。抗扭实验的扭转轴与股骨干成25°,抗压实验的压力轴与股骨干成15°。观察①扭转实验中扭转相同角度时所需的扭矩,股骨颈前部骨折线张开相同程度时所需的扭距。②抗压实验中相同股骨头下沉位移时所需的载荷,相同载荷时股骨颈上部骨折线的张开位移,抗压极限载荷。③愈合模型抗压实验中抗压极限载荷。结果:①抗扭实验结果:在扭转30°以内时,扭矩随扭转角度的增大而增大,并且股骨颈前部骨折线出现分离。扭转相同角度所需的扭矩和股骨颈前部骨折线张开相同程度时所需的扭矩,静态三维钉板系统组均大于滑动鹅头钉组(均P<0.05)。②抗压实验结果:比较股骨头下沉相同位移时所需的载荷、极限载荷以及相同载荷时的股骨颈上部骨折线的张开位移,静态三维钉板系统组与滑动鹅头钉组之间无统计学差异(P>0.05)。③愈合模型抗压实验结果:静态三维钉板系统组的抗压极限载荷大于滑动鹅头钉组[静态三维钉板系统组为(6001±2660)N,滑动鹅头钉组为(2926±1443)N,P<0.05]。结论:①对股骨颈骨折模型的固定,静态三维钉板系统的抗扭力优于滑动鹅头钉,轴向抗压力接近滑动鹅头钉。内固定拆除后骨强度的保留能力,静态三维钉板系统优于滑动鹅头钉。②静态三维钉板系统是一种具有较好生物力学性能的股骨颈骨折内固定器械。

AIM： To undertake a comparative biomechanical study of the stability of static three-dimensional serew-plate system （STDSP）, and evaluate the biomechanical capability of STDSP. METHODS： The mechanical experiment was carried out in College of Aviation and Aerospace Material, National University of Defense Technology between January and February in 2004. Eleven matched pairs of human cadaveric femurs （provided by Department of Anatomy, Suzhou Medical College） were divided randomly into fracture group （8 pairs） and intact group （3 pairs）. In fracture group, vertically oriented femoral neck osteotomies （Pauwel＇s angle 70°） and posterior comminution of the proximal part of fracture model were created and then rearranged into rotation test group （4 pairs） and axial loading test group （4 pairs）. One femur of each pair was stabilized by STDSP, whereas the other was fixed by dynamic hip screw （DHS）. Then the construction was tested with axial loading or rotation. The intact group were fixed as above and taken out with the two methods, followed by destructive axial loading test. For rotational loading, they were secured in a vise at 25° between torque shaft and the shaft of femur; The torques of same rotation angle or anterior fracture line opening in the same angle in neck of femur were both observed, For axial loading, the bone and implant construction were secured in a vise at 15° between pressure axis and shaft of femur. The loading of same femoral head displacement, the opening displacement of superior fracture line in neck of femur in the same loading, and ultimate load were also observed. In additian, the ultimate loads of healed model were obtained. RESULTS： （1）Rotation test： Within 30°, the torque increased with the rotation angle, and the anterior fracture line in neck of femur opened. The load of the same rotation angle and the torque of anterior fracture line opening in the same angle were both bigger in STDSP group than in DHS group （P 〈 0.05）. （2）Axial loading test： Comparing the loads of the same inferior femoral head displacement, ultimate load, and the displacement of superior fracture line opening in the same load, there were no significance between STDSP group and DHS group （P 〉 0.05）. （3）Axial loading test of the healed model： The ultimate load to failure of STDSP group was bigger than that of DHS group [STDSP： （6 001±2 660） N, DHS： （2 926±1 443） N, P 〈 0.05]. CONCLUSION： （1）In order to fix femoral neck fracture models, STDSP is superior to DHS in rotation stability and same as DHS in axial loading stability. In the capability of bone construction strength retention by internal fixation, STDSP is superior to DHS. （2）STDSP is a fixation with good biomechanical features for the treatment of femoral neck fracture.