Three-Dimensional Finite Element Analysis And Clinical Study Of Transverse Fracture Of Patella By Comparison Of Cerclage And Simple Tension Band

Objective: A three-dimensional finite element model of patellar transverse fracture will be established,using tension band and tension band with cerclage as a means of internal fixation is analyzed with mechanics,at the same time,build a clinical retrospective study of two kinds of fixed way,exploring the significance of adding cerclage to improve the clinical effect of using tension band as the fixation method for transverse patella fracture.Methods: In the three-dimensional finite element mechanics analysis,select a case of a healthy adult male knee CT data,based on the patellar transverse fracture model,adopt the tension band and band with cerclage assembly in the form of internal fixation of patella,stress distribution when simulating knee flexion 90 degrees for mechanical load,comparing stress and displacement of patella,fracture surface,Kirschner wire and tension band under different internal fixation methods.When conducting clinical research,the selection is from October,2014 to October,2019,a total of five years,our hospital application of “figure 8” tension band or a “figure 8” + cerclage treatment of patients with closed patellar transverse fractures.after screening out,included in 55 patients,included in the standard for transverse fracture,AO/OTA classification 34-C1 or 34-C2,exclusion criteria for open fractures,history of knee injuries,etc.Among them,there were 16 cases with simple tension band fixation and 39 cases with tension band + cerclage.Preoperative and postoperative X-ray,inpatient records,examination results,inpatient orders,postoperative nursing data,surgical data and anesthesia data were collected,and all cases were followed up.Lysholm knee joint function score was used to evaluate the recovery of joint function.The removal rate of internal fixation device,displacement of Kirschner wire,duration of operation,length of hospital stay and other indexes were used to evaluate and compare the clinical efficacy,and statistical analysis was used to evaluate the efficacy.Results: The three-dimensional finite element results show that the maximum displacement,maximum pressure and maximum sliding distance of the tension band model are 1.97,1.71 and 2.08 times of those of the cerclage model.For the fracture surface,the maximum pressure and maximum sliding distance of the tension band model were 1.79 and 2.02 times of those of the cerclage model,respectively.For the Kirschner wire,the maximum displacement,maximum friction stress,maximum pressure and maximum sliding distance of the tension band model were 1.86,2.12,2.13 and 2.45 times of those of the cerclage model,respectively.In clinical studies,obtained in 55 patients,46 of whom were followed up,8 of whom were lost to follow-up and 1 of whom died.Follow-up lasted from 12 to 71 months,with an average of 36(36.05±19.14)months.There was no significant difference in Lysholm score,removal rate of internal fixation device,operative time and length of hospital stay between tension band alone and tension band with cerclage.For the displacement of Kirschner wires,5 of 12 cases in the tension band group had Kirschner wire slippage,of which 1 case was operated again within 1month due to the failure of the internal fixation device,and 3 cases had the internal fixation device removed after fracture healing.For the 34 cases in the cerclage group,8cases had Kirschner wire displacement,of which 1 case was operated again within 1month due to the stimulation of the implant,and 2 cases had the internal fixator removed after fracture healing.For the patients with Kirschner wire displacement,there was no significant difference in the reoperation rate and internal fixation removal rate between the two groups.Conclusions: For transverse fracture of patella,the results of the three-dimensional finite element mechanical analysis show that adding a cerclage on the basis of traditional tension band can reduce the pressure and displacement of patella and tension band to a certain extent.However,clinical studies have shown that the use of cerclage compared with tension band alone in Lysholm score,Kirschner wire displacement,internal fixation device removal rate,operation time and length of hospital stay showed that the addition of cerclage on the basis of tension band did not significantly improve the clinical effect of simple tension band internal fixation.To sum up,although the three-dimensional finite element mechanics analysis and always mechanics research results are shown cerclage for the tension band fixation effect have certain effect,but in practical application to clinical,the effect is not significant.we can think of that,for the patellar transverse fracture,based on the traditional tension band with cerclage for improving the clinical effects of pure tens ion might with no practical significance.