四种不同内固定方式治疗骨性锤状指的有限元分析

A finite element analysis of four different internal fixations on the stability of bony mallet finger

目的应用有限元分析的方法研究四种不同内固定方式对骨性锤状指稳定性影响。方法对成年志愿者右手行CT扫描,CT图像在Mimics 17.0中进行指骨及软组织识别,Geomagic studio2012拟合出各解剖结构的NURBS曲面模型。在CERO 4.0中构建出四种内固定装置的三维模型,并按照Wehbe和Schneider骨性锤状指分型切割出II型锤状指的三维模型,将上述模型分别装配,建立双克氏针模型、纽扣钢丝模型、8字钢丝模型、微型锚钉模型。在hypermesh中进行划分网格等,然后在Abaqus 6.14中设置载荷及边界条件,计算远指间关节(the distal interphalangeal joint,DIP)屈曲15°、30°、45°时骨折块的平均Mises应力和最大相对位移量。结果(1)双克氏针组中,DIP屈曲15°、30°、45°时,骨折块间的相对位移依次为(0.36±0.15) mm、(0.57±0.11) mm、(0.61±0.17) mm,组内比较差异有统计学意义(P=0.000)。Mises应力分别为(6.21±1.83) MPa、(7.69±1.47) MPa、(8.25±1.61) MPa,组内比较差异无统计学意义(P>0.05);(2)纽扣钢丝组,DIP屈曲15°、30°、45°时,骨折块间的相对位移依次为(0.29±0.03) mm、(0.35±0.09) mm、(0.49±0.15) mm,显著小于双克氏针组(P=0.000)。Mises应力分别为(11.57±3.61) MPa、(12.62±4.18)MPa、(13.81±5.19) MPa,显著大于双克氏针组(P<0.05,a1=0.017,a2=0.021,a3=0.039),但组内比较差异无统计学意义(P>0.05);(3)在8字钢丝组和微型锚钉组中,骨折块的Mises明显高于前两组(P<0.05,b1=0.021,b2=0.016,b3=0.018),并且随着屈曲角度增加,Mises应力明显增加,组内比较差异有统计学意义(P<0.05);(4)四种研究模型中,最大相对位移量由大到小依次为微型锚钉、8字钢丝、纽扣钢丝、双克氏针。结论在微型锚钉、8字钢丝、纽扣钢丝、双克氏针四种不经DIP内固定治疗骨性锤状指的方案中,微型锚钉和8字钢丝能够在不影响DIP功能的前提下为骨折提供良好的愈合环境。

Objective To explore effects of four different internal fixations on the stability of bony mallet finger by a finite element analysis. Methods The right hand of adult volunteer was scanned by CT, and the bones and soft tissues were recognized in Mimics 17.0. NURBS. The finger was fitted in Geomagic studio2012. Four kinds of internal fixation devices and the bony mallet finger model were designed in CERO 4.0. Dual needle model, button wire model, eight steel wire model and anchor screw model were established. Element division was performed in hypermesh, and then load and boundary conditions were set in Abaqus 6.14. The average Mises stress and the maximum displacement of the fracture were tested at 15°, 30°and 45° flexion of the distal interphalangeal joint( DIP).Results( 1) In the dual needle model, the relative displacements between the fracture blocks were( 0.36 ± 0.15) mm,( 0.57 ± 0.11) mm,( 0.61 ± 0.17) mm with statistically significant differences when the DIP flexed at 15°, 30° and 45°( P = 0.000);Mises stresses were( 6.21 ± 1.83) MPa,( 7.69 ± 1.47) MPa and( 8.25 ± 1.61) MPa respectively with no statistically significant differences( P > 0.05).( 2) In the button wire model, the relative displacements between the fracture blocks were( 0.29 ± 0.03) mm,( 0.35 ± 0.09) mm, and( 0.49 ± 0.15) mm when the DIP flexed at 15°, 30° and45°, which were significantly smaller than the dual needle model( P = 0.000);Mises stresses were( 11.57 ± 3.61) MPa,( 12.62 ± 4.18) MPa, and( 13.81 ± 5.19) MPa respectively, which were significantly greater than that of the dual needle model( P < 0.05, a1 = 0.017, a2 = 0.021, a3 = 0.039) with no statistical differences in the group( P > 0.05).( 3) In the eight steel wire model and anchor screw model, Mises stresses were significantly higher than the former two models( P < 0.05, b1 = 0.021, b2 = 0.016, b3 = 0.018). With the increase of the DIP angle, the Mises stress significantly increased within the group with statistically significant differences( P < 0.05).( 4) In the four research models, the maximum relative displacement ranging from large to small were anchor screw model, eight steel wire model, button wire model and the dual needle model. Conclusions In the four models, anchor screw and eight steel wire could provide a stable environment for the healing of fracture without affecting DIP functions.