The biomechanical comparison of original and new dynamic sleeve three-wing screws for femoral neck fracture / 中华骨科杂志

ABSTRACT

Objective To compare the biomechanical property of original and new dynamic sleeve three-wing screws.Methods Twelve artificial polymethylmethacrylate (PMMA) femoral models and twelve adult cadaver femurs were selected,and then adduction-type femoral neck fracture models were prepared.The specimens were divided randomly into 2 groups,and each group had 6 specimens.According to the operative approach,the fractures were fixed with original dynamic sleeve three-wing screw (DSTS) or new DSTS after anatomic reduction.Then the specimens were fixed in simulated uniped standing position with an instron-8874 servo-hydraulic mechanical testing machine.Ten key points at the proximal femurs and two key points at the femoral shaft were selected to be the positions at which the strain was recorded.The continuous load (PMMA group:0-1200 N; cadaver femur group:0-800 N) was put to the specimens at the rate of 10 mm/min.The strain values under the maximum load,the femoral head sinking displacement and the strain values of No.8 gauge under different loads were recorded.Results There was a peak at the No.8 resistance strain gauge under 1200 N in PMMA group,and the strain values of original and new DSTS were (-2744±35) and (-718±14) με,respectively.There was a peak at the No.8 resistance gauge under 800N in cadaver femur group,and the strain values of original and new DSTS were (-2813±38) and (-2032±22) με,respectively.The differences of strain values above were significant.The femoral head sinking displacement of the new DSTS was much less than that of original DSTS under the same load.Conclusion The new DSTS has better biomechanical properties,using which the femoral neck fracture can be fixed more stably.