| ObjectiveA kind of “Strain Gauge Plate” is developed to measure and record the strain on the steel plate automatically and in real time under the external force.Based on the comparison of the strain measured by strain gauge plate in different fracture healing models,a new method to evaluate fracture healing is explored.Methods1.Development of strain gauge plate: The resistance strain gauge was attached to the locking plate,the strain was changed into voltage signal through the Wheatstone circuit.The analog-to-digital converter converted the voltage signal into a digital signal.Finally,the Wi Fi transmitter transmitted the signal to the computer or handset terminal software wirelessly and displayed the strain value.2.Building fracture healing model: State A simulating fracture healing: The “Strain Gauge Plate” was fixed to the intact femur through bridging technology.State B simulating fracture fiber connection: Femur was sawed by wire saw.The same “Strain Gauge Plate” fixed the fracture at the original nail holes with a 1 mm fracture gap.Then the gap was filled with wax.State C simulating fracture nonunion: Femur was sawed off 1cm bone.The same “Strain Gauge Plate” fixed the fracture at the original nail holes with a 1 cm fracture gap.3.Biomechanical test: Selected a sample randomly from 12 fresh goat femurs in state A.Axial compression test and three point bending test were conducted at three different types of screw fixation and in state A,B,C.To determine the screw fixation of “Strain Gauge Plate”,comparisons of strain among three different types of screw fixation were performed via the repeated-measures analysis.To determine the stress distribution of steel plate,comparisons of strain at four different strain points were performed with the repeated-measures analysis.To determine the applied load,the relationship between strain and compression or bending load were confirmed using Spearman’ s rank correlation.To test plate strain being used to evaluate the fracture healing,comparisons of axial displacement,deflection and strain in state A,B,C were performed with the repeated-measures analysis.Results1.The comparison of strain at three types of screw fixation: In the C state of axial compression test and three point bending test,the strain of the second screw fixation was less than that of the first and third screw fixation,p<0.05.2.The relationship between strain and load and the comparison of strain at different strain points: In the A,B,C state of axial compression test and three point bending test,there was a positive correlation between strain and strain,all rs were larger than 0.8,p<0.05.In the A,B,C state of axial compression test(240N)and three point bending test(120N),the strains of point 1 and 2 were larger than that of point 3 and 4,p<0.05.3.Comparison of deformation and strain among three strate of fracture healing: In the axial compression test(240N)and three point bending test(120N),the axial displacements and deflections of steel plate-bone system among state A,B,C were different significantly,strain in state A<strain in state B<strain in state C,p<0.05.In the axial compression test(240N)and three point bending test(120N),the strain of state A,B,C were different significantly,strain in state A<strain in state B<strain in state C,p<0.05.Conclusions1.Follow the principle of “large span and less screws”,steel plate strain could be reduced effectively and the ability of steel plates to resist deformation was enhanced.2.The stress of steel plate was mainly distributed near the nail holes.When three points bending force were applied to steel plate,the stress was mainly concentrated at the fracture end.3.The “Strain Gauge Plate” can be used to evaluate the degree of fracture healing by measuring strain.A new hope was brought to clinical evaluation of fracture healing,guidance of quantitative functional training and early warning of plate fracture and screws looseness. |
