Biomechanical study of different internal-fixations in femoral neck fractures / 中华创伤杂志

ABSTRACT

Objective To compare the biomechanical effect of several commonly used internal fixators in treating the femoral neck fractures so as to provide clinical basis for the selection of ideal internal fixation.Methods Twelve artificial PMMA femoral models were selected,and the central neck of the specimens was sawn with an electric saw at Pauwels angle of 70° to form adduction type femoral neck fracture models.After anatomic reduction,the specimens were fixed with dynamic hip screw ( DHS),three hollow screws,proximal femoral nail (PFN) and dynamic sleeve three-wing screw according to the operative approach,respectively.Instron-8874 servo-hydraulic mechanical testing machine was used to fix the specimens which simulated uniped standing.Fifteen key points on proximal femur were selected as test points and were given gradation loading at speed of 10 mm/min with linear load 0-1 200 N.The strain of each point under 1200 N load,head sink displacement under different loads and the strain of eight points on principal pressure side were measured.Results There was a peak at the eight resistance strain gage at 1200 N load and the strain values of the DHS,three hollow screws,PFN and dynamic sleeve three-wing screw were (700 ±35) μεz,(756 ± 14) με,( 1362 ± 136) με and (3024 ± 127) με,with statistical significance (P ＜ 0.01 ).Under the same load,the head sink displacement in the group of dynamic sleeve three-wing screw was greater than that of the hollow screws group and the PFN group ( P ＜0.01 ),but smaller thau that of the DHS group ( P ＜ 0.01 ).The strain values at the eight resistance strain gage in the group of dynamic sleeve three-wing screw was larger than that of the other three groups under the same load (P ＜ 0.01 ),and the strain values increased with the increase of load at the same fixation group.Conclusion Dynamic sleeve three-wing screw has good biomechanical stability for treatment of femoral neck fracture,which can be applied in the clinical practice.