| The internal fixation with bone plate is one of the important methods in treating long bone fractures. As the representative of conventional plate, compression plate is currently the most popular fixed system of bone plate. The rigid internal fixation by compression plate can provide stable mechanical environment for bone healing and functional recovery. However, in clinical practice, osteoporosis due to compression plate is the main cause of re-fracture after removing the plates. According to this problem, researchers think that bone may occur in response to either altered cortical perfusion or stress shielding. Considering maintaining regional circulation and reducing stress shielding, modifying the conventional compression plate has been a highlight in the study and application of bone plate. Based on biomechanical fixation and biological fixation, and the structure of the compression plate of gear contact half cycle and channel type (GCC), the author developed a new kind of internal fixed system of compression plate of gear contact plate-band and channel type (GCPC), then applied it to femur fractures and studied its biomechanical effect of fixing femur fractures, expecting to improve biomechanical property of conventional plate and provide experimental basis for clinical work. Materials and methods:Eight pairs of fresh and moist human cadaveric femurs harvested from eight specimens of adults (provided by Anatomical Department of Shanghai Second Medical University), there were three females and five males. The specimens were aged betweenthirty-nine and fifty years old at the time of death, weighing 56kg on average (range: 47-65). After removing the soft tissue, the proximal and distal ends of femurs were cemented with polymethyl methacrylate (PMMA), and stored in a refrigerator at-20 until the day of the study. Before testing, each femur was thawed in Ringer" s solution at room temperature of 20 for three ~ four hours. All have no known skeletal pathology by plain radiographs.The femurs were assigned randomly to the experimental group (n=eight femurs) and the control group (n=eight femurs). All specimens of the experimental and control group were sawed transversely to the model of fracture of femoral shaft by the control osteotomy, these fracture models should be as consistent as possible. The femurs in the experimental group were fixed with GCPC and the femurs in the control group were fixed with general compression plate (GCP), Plate fixation was accomplished by standard AO technique, all plates were made of stainless plate 316L. On the basis of the simulation of the standing phase with load on single leg, the load type and load scope were decided as follows: the axial compression load and the bending load were done from ON to 500N, and torsional load of ONm to 20Nm, with a load speed of 1 .4 mm/min, Classified loading way was adopted, the maximum load was chosen to approximate ninety percent of the average body weight of all specimens.The procedure of the test consisted of axial compression test, three-point bending test and torsion test. In each testing, the femur was firstly loaded with a tenth of pre-load for ten times at the velocity of 1.4mm/min, in order to eliminate the effect of the viscoelasticity of femur. In axial compression test, the intact femur was firstly exerted with two main loads of 400N and 500N, with a load speed of 1.4 mm/min, two corresponding strain values were recorded. Subsequently the fixed femur was carried out by the loads from ON to 500N. In three-point bending test, the loading point was situated in the midpoint of the middle two holes of the plate. The specimens were kept moist throughout the procedure. All the experimental data were expressed as mean ?standard deviation, using the SPSS10.0 software. Student's t test was employed to verify the significance of the data. And a P value<0.05 was considered as significant difference.Results:1 . Axial compression test. At every classified load, strain and displacement of the experimental group were greater than them of the control group (... |
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