不同角度植骨和空心钉固定股骨颈骨折的生物力学研究

Biomechanical study of femoral neck fracture fixed by cannulated screws and iliac bone graft at different angles

目的探讨游离髂骨块不同角度植骨、空心钉固定股骨颈骨折的生物力学效果,为临床应用提供生物力学依据。方法选用9对成人防腐股骨标本,随机分入0°角植骨组和30°角植骨组。所有标本均制成股骨颈骨折模型,解剖复位后采用3枚空心钉及髂骨块固定,空心钉呈正等腰三角型分布,髂骨块越过骨折线约1.5 cm,其中0°角植骨组髂骨块位于三枚空心钉中间,并与其平行,30°角植骨组髂骨块与空心钉成30°角。2组标本均应用Electroforce 3520-AT生物力学实验机进行抗扭转、抗压、循环载荷及极限载荷实验。结果抗扭转实验中使股骨头扭转3°和5°时,30°角植骨组扭矩值均大于0°角植骨组(P均<0.05);抗压实验中在700 N和1 000 N的垂直载荷下,30°角植骨组位移值均小于0°角植骨组(P均<0.05);所有标本均成功完成了循环实验,无疲劳骨折、内固定失败出现。30°角植骨组能够承受的极限载荷比0°角植骨组大11.7%(P<0.05)。结论采用3枚空心钉固定股骨颈骨折时,30°角植骨的生物力学稳定性优于0°角植骨,本实验结果为临床上治疗股骨颈骨折采用最佳的植骨方式提供了生物力学依据。

Objective To investigate the biomechanical stability of iliac bone grafts at different angles with three cannulated screws for fixation of femoral neck fractures in order to provide scientific basis for clinical application.Methods The nine pairs of proximal femora and ipsilateral iliac bone grafts with lateral and upper surface retaining cortex were harvested from nine cadavers fixed in formalin,which were randomly divided into two groups： cannulated screw with medial bone graft fixation group （ CMB group） ,cannulated screw with cross bone graft fixation group （ CCB group） .The specimens were cut with power saw to create a standardized midcervical osteotomy perpendicular to the cervical neck.The fracture was then reduced and fixed with three parallel 7.3mm cannulated screws and an iliac bone graft.The cannulated screws were placed triangularly with one screw superior and two inferior.In the CMB group,the bone graft was in the middle of three cannulated screws and parallel with it,however,in the CCB group,the bone graft was made an angle of 30°with the screws on postero-anterior position.All the bone grafts were passed across the fracture line about 1.5cm.Every specimen was detected by Electroforce 3520-AT biomechanical machine.Results When femoral head was rotated to 3°and 5°, the torque values in CCB group were significantly higher than those in CMB group （ P 〈0.05） ,however,during axial displacement at the load of 700N and 1000N, the displacement values in CCB group were significantly lower than those in CMB group （ P 〈0.05）.All the specimens underwent cycling compression test at 700N compression force successfully,without fatigue fracture or screw failure.The mean ultimate load in CMB group and CCB group was （2112.689 ±186.913）N and （2360.811 ±204.340）N,respectively,there was a significant difference between two groups （ P 〈0.05）.Conclusion The biomechanical stability of fixation of femoral neck fracture with three cannulated screws in CCB group is superior to that in CMB group,and the experimental results provide a biomechanical basis for adopting optimal bone graft mode in the treatment of femoral neck fracture.