The Biomechanical Study Of Double Dynamic Compression Interlocking Nail In The Femur Cross-sectional Fracture

Objective: To test the bio-mechanical index of double dynamic compressional interlocking nail in the femoral transverse fracture model at manual pressure and mechanical pressure process ,compared it with static interlocking nail, sum double dynamic compressional intramedullary nail's biomechanical characteristics.Methods: Use 16 adult femoral specimens, removing muscle tissue, after gross observation, x-ray exame in order to ruled out bone disease and other bone disease,test and record the strain intact femur first, cutting the femur at middle part by the wire saw ,made it into transverse fracture model of femur. Divided them into two groups,there are 8 models in each group,fix the fracture model by ordinary static intramedullary nail and double dynamic compressional nail from Strkey company . Paste the strain gauges at the vicinity of the fracture resistance, as a r fixed top and bottom to respectively cast parallelly to each other by self-curing denture powder, eliminating creep of ends, test strain and displacement in the fracture site change of two models with 0 ~ 500N axial load during manual compression, after the completion of manual pressure, test the parameters of reverse and the three-point bending between model of double dynamic compressional and static interlocking nail . Then, give an axial mechanical compression on the fracture to test the strain and displacement of fracture fragments with 500 ~ 4000N load, and calculate the stress shielding rate, Analysis the differences of mechanical result, evaluate their significance.Results: In the manual compression process, the axial compression strain and displacement generated of the double dynamic compressional interlocking nail was more than ordinary static intramedullary nail (P <0.05), which promote fracture contact closely. The parameters of three-point bending and reversing were no statistical difference between Static intramedullary nail group and the double p dynamic compressional nail group in mechanical process (P >0.05). In the mechanical pressing process, the strain from axial compression direction of double dynamic compressional interlocking nail group is less than the static intramedullary nail group (P <0.05), displacement is the opposite. And the nail of static interlocking nail was shear deformation early than dynamic compressional interlocking nail in the process of mechanical pressure increases with the load increase.Conclusion: The double dynamic compressional intramedullary nail make fracture contact close during manual compression process ,it provide a stable and reliable environment for mechanical transmission.It'mechanical properties of torsion and bending has no significant differences to static interlocking nail group (P> 0.05). In process of Mechanical compression, the double dynamic compression intramedullary nail'Motorized design increased Conduction of stress through the Fracture site and reduce the shear locking nail.