| Objectives This study designed different configurations of hybrid external fixation.Biomechanical tests were done to investigate mechanical properties of fixing type A2 tibial shaft fractures with different configurations of the hybrid external fixation.Verifying its curative effect of through clinical treatment It provided a certain theoretical basis for the rational,standardized and effective establishment of hybrid external fixation to guide clinical diagnosis and treatment.Methods The basic components for designing hybrid external fixations are the fixed pins and the connecting rod.A total of 10 types of external fixation configurations have been designed and completed,respectively for 1 to 10 frame configurations.Tibial A2 fracture specimens(including proximal and middle segments)were respectively fixed in each style of configuration.According to the different positions of fracture,the external fixation models were divided into the middle tibia fracture model fixed group(group A)and proximal tibial fracture model fixed group(group B).The biomechanical test of universal mechanics testing machine(Bose Electro Force Electro Force 3510)was carried out in the Department of orthopedics,Institute of biomechanics,Department of orthopedics,including axial compression test,torsion test and three point bending test.The results were recorded and analyzed statistically.The patients who were treated fracture of the leg with hybrid external fixation in our hospital from April 2014 to June 2016.The patients were fixed with a self designed combined external frame for fracture fixation,regular follow-up after operation and removal of external fixation after the bone healing.During the followup period,we evaluated fracture healing,lower limb shape and joint mobility.JohnerWruhs effect analysis was used to evaluate the postoperative curative effect.Results 1)Biomechanical study:(1)To compare the different configurations of external fixation compressive resistance: In group A,the axial stiffness [232.37+4.676)N/mm,(221.26+2.267)N/mm] and torsional rigidity [(2.12+0.057)N/Deg,(1.99 + 0.024)N/Deg]of configuration 5 were the largest,and the anti-compression and anti-rotation ability were the strongest.The configuration 2 to 4 were following.The axial stiffness [(104.77±0.547)N/mm,(109.77±0.551)N/mm] and torsional stiffness [(1.38±0.018)N/Deg,(1.37±0.008)N/Deg] of configuration 1 were the smallest,and the anticompression and anti-rotation ability were the weakest.The anti-torsion and anticompression ability of the configuration 5 to the configuration 1 was decreasing(P<0.05).Under the same load,the displacement difference of 5 bars and 4 bars frame models were greater than 5 bars and 6 bars frame models.With the increasing of the load,the former was significantly increasing trend and the latter did not change significantly.It suggested that the 5 bars and 6 bars models of anti-compression and anti-rotation ability were similar(2)To compare of the bending resistance of different configurations of external frame: This experiment was carried out in the external frame model of the group A.The configuration 5 has the strongest anti-bending abiliby.The configuration 2 to 4 were following.The configuration 1 had the weakest anti-bending abiliby.The anti-bending abiliby of the configuration 5 to the configuration 1 was decreasing(P<0.05).2)Clinical study: This study selected 20 patients,inclued male 12 cases,female 8 cases,mean age 32.3±5.6 years old.The reasons of injuries included traffic accident injury in 11 cases,crush injury in 4 cases,machine crush injury in 2 cases,3 cases of injury caused by other reasons.All cases were treated by the external frame configuration designed by this subject.After operation,the fracture were well combined,the external frame was firmly fixed,no serious infection and other complications occurred.During the hospitalization,there were 1 cases of needle leakage and 1 cases of partial necrosis,which gradually improved after dressing change.All patients were followed up for 9-24 months.All patients were healed,16 cases were healed at one stage,which rate was 80%;3 cases were delayed healing(15%),and 1 cases was nonunion(5%).After the removal of the extrenal frame,the appearance of the lower limbs was satisfactory.After the rehabilitation practice,the joint function recovered well.The evaluation and evaluation results of the final follow-up Johner-Wruhs efficacy analysis showed that 15 cases were excellent,3 cases were good,2 cases were in the middle,0 cases were poor,the excellent rate was 90%.Conclusions 1)Between the hybrid external fixations designed in this study,the configurations of 6 bars(configuration 5 and configuration 10)have the best stability.The configurations of 4 bars(configuration 1 and configuration 5)have the worst stability.Increasing the number of connecting rods could significantly enhance the stability of the external frame.2)The external fixations with the configuration of 5 bars(configuration 2-4 and configuration 7-9)had different mechanical properties with connecting rods arrangement.The configuration 4 and configuration 9 were the best for stability.3)Clinical studies confirm that the external fixations of 5 bars designed by our research have strong stability,which can better meet the clinical needs for fracture treatment.They are relatively economic,efficient and convenient.It has good fracture fixation effect,high healing rate,and high clinical application value. |
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