股骨交锁髓内钉锁钉断裂的生物力学研究

Biomechanical study on the interlocking nails breakage of femoral interlocking intramedullary nail

目的测定股骨交锁髓内钉锁钉的生物力学变化,分析锁钉断裂的原因及位点。方法取6具青壮年全长防腐股骨标本,剔除软组织后远端用牙托粉包埋固定,装于MTS试验机,锁钉处安装位移传感器,轴向加载0～500N,速度为50N/s。每具标本模拟6个状态a正常股骨;b骨折愈合;c稳定骨折;d稳定骨折远端去除1枚锁钉;e,不稳定骨折;f,不稳定骨折远端去除1枚锁钉。分别测量各锁钉处应变变化,并进行统计学分析。结果近端锁钉间应变在各种状态下均无显著性差异(P>0.05);近端锁钉与远端锁钉之间应变存在显著性差异(P<0.05);远端去除1枚锁钉固定时剩余远端钉表现比原来的应变大。第3枚锁钉在所有状态之间均有显著性差异(P<0.05)。结论骨折线远端的锁钉易发生断裂,尤其是靠近骨折线者;尽量以2枚锁钉固定远端并远离骨折线。

Objective:To analyze the causes of interlocking nails breakage and which nail tend to being broken by testing the biomechanical strain changing of interlocking intramedullary nails.Method:Six antiseptic adult femora,with all soft tissue cleared and the distal tip coated by dental base acrylic resin powder,were used.Specimens were fixed and installed on MTS machine,and migration sensors were put on each inter-locking nail.The axial load was 0～500N at 50N/sec.Each specimen was tested as six conditions:a,normal;b,cured fracture;c,stable fracture;d,as c and a distal interlocking nail removed;e,unstable fracture;f,as e and one distal nail removed.The strain changing of every interlocking nail was measured and statistical analysis was done.Result:There was no significant strain changing of proximal interlocking nails (P>0.05);the changing between distal and proximal was significant(P<0.05);in the groups with only one distal nail fixed,the distal nail had to bear more strain.The third nail had significant strain changing in all conditions.Conclusion:Interlocking nails below the fracture line,especially near it,tend to be broken,so that two interlocking nails should be applied to the distal fracture fragment and the interlocking position should be far enough away from the fracture line.