新型胫骨动力加压交锁髓内钉治疗不稳定骨折的力学性能分析

Biomechanical study of grooved interlocking dynamic compressing medullary nail for unsteady fractures of tibia

目的研制具备动力加压功能的新型胫骨交锁髓内钉,并分析其在胫骨不稳定骨折治疗中的可行性及力学性能。方法男性健康成人防腐尸骨胫骨湿标本45根,随机分左右侧进入不同实验组,按骨折髓内钉及加压钢板内固定的标准手术操作进行内固定后,于胫骨结节上缘至踝关节平面连线中点锯断,制成骨折端间隙环形扩大至5 mm的不稳定骨折模型。新型髓内钉组:新型胫骨髓内钉25套,直径8 mm,长度280 mm。对照组:分为进口髓内钉对照组及AO加压钢板对照组,其中髓内钉对照组为orthofix胫骨髓内钉10套,规格与实验组相同;胫骨8孔AO加压钢板10套为钢板对照组。各组分别进行轴向压缩试验、三点弯曲试验及扭转试验,对不稳定骨折模型的不同内固定方式的抗轴向压缩、抗侧弯、抗旋转力学性能进行测试比较。结果不稳定骨折情况下,钢板对照组的抗轴向压缩能力最差,新型髓内钉组的抗短缩能力不及髓内钉对照组,组间差异有统计意义(P<0.01)。新型髓内钉组的抗侧弯稳定性明显优于髓内钉对照组,3组中钢板对照组抗侧弯性能最优,组间差异有统计意义(P<0.05)。随骨折稳定性的下降各组抗扭转性能均有不同程度下降。新型髓内钉组的抗扭转性能次于钢板对照组而优于髓内钉对照组(P<0.05)。结论新型髓内钉的综合力学性能具有明显优越性,其力学性能可保证骨折端的复位和固定要求。

Objective To manufacture a new type of interlocking medullary nail which has dynamic compressing function and then discuss the possibility and acknowledge virtues of the new nail in treating unsteady tibial fractures. Methods A total of 25 pairs of tibial medullary nails （ Ф =8mm, length=280 mm） were involved as the test group,10 imported orthofix nails and 10 AO compressing plates were taken as contrapose, and 45 tibias were divided into different test groups by left and right at random. We widened the fracture clearance to 5 mm and obtained the unsteady fracture models after bone fixed by three kinds of devices. The anti-axile compression, anti- lateral bending and anti-torsion property of the new interlocking dynamic compressing intramedullary nail were tested and compared with those of orthofix interlocking intramedullary nail and AO dynamic compression plate in treating unsteady tibial fracture to assess the reliability of the new nail came in cases of unsteady fractures. Results In the cases of unsteady fractures, the imported orthofix nail presented best anti-pressure performance and the new nail came second, the AO compressing plate was the worst, with significant differences （P〈0.01）. At the beginning of three-point bending, the flexibility was due to the small clearance between the nail and the cortex. The AO compressing plate provided best fixation in both tests of anti-lateral bending and the anti-torsion, and the new nail performed second best, with obvious differences （P〈0.05）. Conclusion In unsteady tibial fracture, the newly developed nails has superior biomechanical characters, and the reposition and fixation are reliable and better.