| Objective: According to the characteristics that there is a prone to the development of femoral head collapse ,Coxa vara, resulting in failure of internal fixator in elderly hip fractures,We designed a new type of external fixator of hip fracture, which can overcome the existing shortcomings, provide a special device of rational design, simple operation, lightweight and securation.For hip fracture patients those are difficult to be treated by internal fixator,it can play a complementary treatment to solve the current part of the treatment problem of hip fracture. The purpose of this study is to discuss the bio-mechanical properties of treating intertrochanteric fractures through the calf body femoral specimens biomechanical testing by hip slide- poking external fixator,and provide a scientific basis for clinical application.Methods: According to anatomical data of hip and the need of enough slide- poking functional requirements, we designed the hip fracrure slide- poking external fixator and took biomechanical testing between hip fracrure slide- poking external fixator and DHS: We selected 9 pairs of fresh bovine corpse femur specimens of similar BMD and in one-year-old . By matching left and right foot,they were divided into A (left), B ( right) groups, each group had 9 specimens. Along the intertrochanteric wire, type 31-A1.3 model intertrochanteric fracture was made.Each left femur specimen was fixed by DHS (control group), right was fixed by slide- poking external fixator (experiment group). Simulating the human body on one- leg standing position (frontal plane adduction 25°, sagittal plane neutral position), the specimens were casted with a constant fixture in denture powder. The A, B group vertical loading experiments: The fixed specimens were placed in biomechanical machine, giving the femoral head straight down grading load, corresponding subsidence of femoral head were recorded in the experimental group and control group loaded into the 100N, 200N, ... 1000N gradually; Then A, B group torsion test: The specimens would be upside down, the femoral head down, the two ends were connected to the biomechanical test machine, doing torsion test, maintaining proximal femoral stationary, the machine clockwise (left femur) or counterclockwise (right femur) reversed the direction of the distal femur, and the speed was adjusted by the machine itself , torsion angle values were recorded in the experimental group and control group torqued into 1,2,3, ... 10 Nm gradually. Statistical analysis: All data were mean±standard deviation, with SPSS16.0 statistical software to handle all data and paired t test (biomechanical tests), P <0.05 difference between the two groups was statistically significant data.Results: The slide- poking externalfixator in hip fracture has been designed and developed;In the vertical loading experiment, loaded into the 1000N, the femoral head down the vertical displacement of the experimental group was 1.49322±0.116280mm, the control group 2.13656±0.166374mm; In the reverse experiment, when the time to reverse the 10.0Nm The experimental group torsion angle value was 7.9733±1.65704°, the control group was 15.4889±0.73228°. Biomechanics experimental datas of the two groups were statisticed by paired t test,and the results were all P <0.01 <0.05, demonstrated that the resistance to compression (bending) and anti-rotation strength of hip slide -poking external fixator was significantly stronger than that of DHS.Conclusion: The slide- poking externalfixator in hip fracture has been designed and developed; Biomechanical experimental datas show that the resistance to compression (bending) and anti-rotation strength of hip fracture slide -poking external fixator is significantly stronger than that of DHS and that in clinical hip fracrure slide- poking external fixator can provide sufficient resistance to compression (bending) stability, good anti-rotation biomechanical properties. |
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