数字散斑法测量股骨干骨折髓内钉内固定下的形变

Measurement of the deformation of interlocking intramedullary nail for femoral fractures with digital speckle correlation method

目的:用数字散斑法测试髓内钉锁钉的形变,为临床上分析锁钉断裂之原因提供理论依据。方法:取4根成人防腐股骨标本,制作股骨中段交锁髓内钉内固定模型。4枚锁钉从上到下标记为1,2,3,4。每具标本分A-D组测试顺序进行测试,A组:安装交锁髓内钉模拟骨折愈合;B组:在A组基础上股骨中段横形锯断2次,即中点锯断1次,中点下5 cm处行第2次锯断,模拟较复杂型骨折;C组:在B组的基础上上端去除1枚锁钉;D组:在C组基础上下端去除1枚锁钉。分别测量4组第4锁钉的形变。在100,300,500 N拉力下,CSS-44100型电子万能试验机测量数据,数字散斑相关软件计算得出应变。结果:在300 N拉力下B组与C组差异有统计学意义(P<0.05)。结论:髓内钉内固定远端锁钉易发生断裂,应尽量以2枚锁钉固定远端。

Objective To provide a theoretical basis for clinical analysis of the reasons of nail fracture by measuring the deformation of interlocking intramedullary nail with the digital speckle correlation method. Methods Four femoral specimen of adults were taken. An intramedutlary nail fixation model in the femur was made. Four lock nails were marked from top to bottom as number 1, 2, 3, 4. Group A, B, C and D were measured in orders. In group A, the femur was not sawed with intramedullary nail placed inside the femur shaft marrow （simulation of the cured fracture）. In group B, the femur was sawed on the basis of group A in order to simulating more complicated fracture （fractured twice on the half of the femur, the center point of femoral shaft was sawed up once, under the center point the 5 cm place line of the second time was sawed up）. In group C, a nail of the upper end was removed on the basis of group B. In group D, a nail of the lower end was removed on the basis of group C. The deformation of the forth nail was measured in 4 groups, respectively. Under the force action of 100,300,500 N, the related data were measured by CSS-44100-electronic universal testing machine, and the deformation was calculated by digital speckle correlation method. Results There was a statistic difference between group B and C under 300 N （P〈0.05）. Conclusion The distal nail of femoral interlocking intramedullary nail internal fixation is easily broken. It is suggested to perform distal fixation by two lock nails.