| A new kind of internal fixture, intramedullary expanded self-locking nail(IESN), was applicated, which was easy to be used in for femur fractures. In order to provide experiment and clinical date for safe clinical practice, this study aimed to evaluate intramedullary expanded self-locking nail for femur fractures.These parts comprised in this paper.1. The first part of this study.Objective:A new kind of internal fixation, witch without the orthodox lockpin—the standard spencimen of expanded self-locking nail(IESN), a biomechanic test were made. Methods: six pairs fresh adult moist cadaveric femur specimens were used to manufacture bone model about 10cm. Group 1 were fixed using the standard specimen of intramedullary expanded self-locking nail and group 2 were fixed by the standard specimen of homemade interlocking nail. All specimens were made biomechanic test and the data was analysed by static SPSS13.0 software. Results :The stiffness of group 1 in resisting rotation and axial displacement and resist bending were smaller than that of the group 2. But there was not static different between two groups. Conclusion: the standard spencimen of IESN had fine biomechanical characteristics in fixation for femur fractures, especially in auti-axial tension and bending.2.In the second part of this study, the biomechanical tests of intramedullary expanded self-locking nail for femur fractures were evaluated in vitro. Objective:To test and evaluate the biomechanical function of expanded locking nail(IESN), A new kind of internal fixation without the orthodox lockpin. Methods:six pairs of fresh adult cadaveric femur specimens were divided into two groups. Each femur was given a fracture at 1/2 shaft, and then kept 1.5cm bone gap by using IESN or homemade interlocking nail respectively. All specimens were given a biomechanical test on axial displacement and rotation resistance and bending. and the data was analyzed by SPSS13.0. Results The stiffness of group 1 in resisting rotation and axial displacement and resist bending were smaller than that of the group 2. But there was not static different between two groups. Conclusion Being used in femur fracture, the internal fixture of intramedullary expanded self-locking nail was firm and dependable, with more power resisting rotation and axial displacement and resist bending of the function, and accorded with the principle of biology fixation. It would be widely used in clinical practice.3.The third part of this study is finite element analysis of intramedullary expanded self-locking nail. Objective: Two intramedullary nail were used to fix fracture of femoral shaft, which were compared on the distribution of stress by means of finite element method(FEM). Through analysis:○1Predict the optimal indication of the intramedullary expanded self-locking nail;○2 Estimate the risk of nails and/or expend-claw broken following fixation. Methods: The finite-element models of femoral shaft fracture which fixed with Intramedullary expended self-locking nail(IESN) and intramedullary interlocking nail(IILN). The stress of models were detected under vertical loads, walking and torsion loads(0-50Nm). Results:○1All of the loads,the maximum stress in bone-impant–complex(BIC) of ZS is larger than of CT.○2The BIC-ZS and BIC-CT could keep elasticity when give under 25Nm torsional moment at the proximal of the femur.○3 Fatigue times test: The times of IESN are 1.9E+13and the times of IILN are 2.3E+13 under 0-1.2 times of the body weight axial stress.○4The failure loads of the IESN is 2175.2N, and the IILN's loads is 2591.8N. Conclusions: 1.The most suitable cases of fixation with the IESN are those with femoral fracture in the middle of the shaft. 2. The IESN is one instrument with rational construction and good biomechanical, and it can be fix femoral shaft fractures safely. 3. The IESN may be partly instead of the IILN. All about of the conclusions need to confirm in clinic practice. |
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