Biomechanical comparision of femoral intramedullary nails for interfragmentary rotational stability
Ahmet Adnan Karaarslan1, Hakan Aycan1, Aslan Mayda1, Fatih Ertem2, Erhan Sesli1
1Department of Orthopedics and Traumatology, Medical Faculty of Şifa University, İzmir, Turkey
2Department of Biomechanics, Dokuz Eylül University Institute of Health Science, İzmir, Turkey
Keywords: Femoral nail; femur fractures; fracture union; interfragmentary distraction; interfragmentary rotation.
Objectives: This study aims to investigate which intramedullary nail is biomechanically better for establishing interfragmentary rotational stability. Materials and methods: Thirty composite femurs were utilized in this study. We analyzed interfragmentary rotational arc displacements between 10 Nm external-6 Nm internal torques and 6 Nm external-6 Nm internal torques which imitate rotation torques while walking on a flat surface and descending stairs by administering 10 interlocking nails, 10 compression nails, and 10 Mehmet anti-rotation nails with tube compression.
Results: Maximum interfragmentary rotation arc displacement between 10 Nm external rotation and 6 Nm internal rotation torques was mean 1.64 mm in the Mehmet nail compressed by 7 Nm torque wrench. This value was lower by 309% (6.72 mm) from interlocking nail (p=0.000), 201% (5.42 mm) from compression nail compressed by 2.5 Nm torque wrench (p=0.000), and 26% (1.92 mm) from compression nail compressed by 7 Nm torque wrench (p>0.05).
Conclusion: In axially stable transvers and short oblique femur fractures, Mehmet nail is superior to other intramedullary nails with limited movement between locking screw and hole, more interfragmentary compression without locking screw deformation, and no proximal nail migration.