Objective:The biomechanical study of three kinds of internal fixations was performed in order to get the best treatment of femoral shaft fracture in child.Methods Three triangular needles,cloverleaf nails and plate were used respectively as internal fixators in10femoral specimens from child corpses and subjected to biomechanical tests.Results1.Three point bendings①Under Anterior loading,the rigidity of triangular needle was medium,its remnant deformation was smallest.②Lateral loading,the rigidity of triangular needle was smallest,its rem-nant deformation was medium.③Under Lateral downward loading(40mm),the remnant deformation of triangular needle was smallest.2.Torsive tests:①The rigidity and the remnant angle of the triangular needle were medi-um when it was rotated externally and internally.②The remnant angle of the triangular needle was smallest when it was rotated externally15°.Conclusion The biomechanical experiments of three point bending and tor-sive tests proved that the triangular needle had good elasticity,best restorable function and strongest anti-rota-tion force.The use of three triangular needles of internal fixation for the treatment of child femoral shaft frac-ture was evidently better than those of cloverleaf nail and bone fracture plate.