Finite Element Analysis And Clinical Study On Internal Fixation Of Tibial Pilon Fractures Based On The Comprehensive Classificaion

ObjectiveAncient Chinese doctors have already had a deep understanding of ankle fractures.For the treatment of the tibial Pilon fracture,early fracture reduction is the basis.Internal and external treatment of Chinese medicine as well as acupuncture and moxibustion can be effective in the healing of such fractures.The comprehensive classification of tibial Pilon fracture has been recognized and valued by scholars both at home and abroad since it has been put forward since2010.However,the theory of internal fixation is still lacking in biomechanical basis and controlled clinical research.Then the finite element analysis（FEA）technology is used to perform simulated surgery and biological operations on four types of Pilon fractures including varus,valgus,dorsiflexion and plantarflexion.On the basis of mechanical analysis,the stability of the four types of fractures with different internal fixations will be evaluated,which provided a biomechanical basis for clinical treatment of tibial Pilon fractures.A retrospective clinical analysis on the efficacy of tibial Pilon fracture based on the comprehensive classification will be observed in order to verify the biomechanical finite element results,and provide a effective choice of the fracture treatment clinically.MethodsThe first chapter consisted of a biomechanical finite element analysis of different internal fixation methods for varus and valgus tibial plion fractures.GroupⅠ（varus type,the main fractures locate in the medial side of the ankle joint）:The main support plate of groupⅠ_Awas placed in medial side of the distal tibia,the main support plate of groupⅠ_Bwas placed in anterolateral side of the distal tibia.Group II（valgus type,the main fractures locate in the lateral side of the ankle joint）:the main support plate of group II_Awas placed in anterolateral side of the distal tibia,the main support plate of group II_B was placed in medial side of the distal tibia.In both groups,a locking plate was placed on the lateral side of the distal fibula.Respectively in normal standing ankle and varus 15°and valgus 15°,axial load was applied in finite element analysis.The second chapter consisted of a biomechanical finite element analysis of different internal fixation methods for dorsiflexion and planter flexion tibial plion fractures.GroupⅢ（dorsiflexion type,the main fractures locate in the front side of the ankle joint）:The groupⅢ_Awas fixed with the plate and screws system in anterolateral of the distal tibia.The groupⅢ_Bwas fixed with hollow screws system on the front of the distal tibia.GroupⅣ（planter flexion type,the main fractures locate in the posterior side of the ankle joint）:The groupⅣ_Awas fixed with the plate and screws system in the posterior of the distal tibia.The groupⅣ_Bwas fixed with hollow screws system in posterior of the distal tibia.In both groups,a locking plate was placed on the lateral side of the distal fibula.Respectively in normal standing ankle and dorsiflexion 15°and planter flexion 15°,axial load was applied in finite element analysis.In Chapter 3,retrospective analysis was taken on 84 patients with comminuted tibial Pilon fractures,who were admitted from June 2013 to October 2016,was divided into two groups according to the surgical principle.The experimental group called comprehensive classification group（44 cases）included 15 cases in varus group and 12 cases in the valgus group,8 cases in the dorsiflexion group and 9 cases in the plantar flexion group.The control group called AO/OTA classification group（40 cases）included 12 cases were type 43B and 28 cases were type 43C.Among them,19 cases of main supporting plates were placed on the anterior or anterolateral side of the distal tibia,12 cases were placed on the medial side,and 9 cases were placed on the posterior side.A comparative analysis was performed on the quality of fracture reduction and recovery of ankle joint function in both groups.ResultsIn the first chapter,the maximum stress of the tibial,the fracture end stress and the axial displacement of the fracture end are compare under the axial stress load.Group I is varus type of which plate was placed on the medial in I_Aand on the anterolateral in I_B.When the ankle model is in neutral position,I_A<I_B.When the ankle model is 15degrees inside,I_A1<I_B1.When the ankle model is 15 degrees outside,I_A2<I_B2.Group II is valgus type of which plate was placed on the anterolateral in II_Aand on the medial in II_B.When the ankle model is in neutral position,II_A<II_B.When the ankle model is 15 degrees inside,II_A1<II_B1.When the ankle model is 15 degrees outside,II_A2<II_B.Internal fixation maximum stress is compare under the axial stress load.Group I is varus type of which plate was placed on the medial in I_Aand on the anterolateral in I_B.When the ankle model is in neutral position,I_A>I_B.When the ankle model is 15 degrees inside,I_A1>I_B1.When the ankle model is 15 degrees outside,I_A2>I_B2.Group II is valgus type of which plate was placed on the anterolateral in II_Aand on the medial in II_B.When the ankle model is in neutral position,II_A>II_B.When the ankle model is 15 degrees inside,II_A1>II_B1.When the ankle model is 15degrees outside,II_A2>II_B.In the second chapter,the maximum stress of the tibial,the fracture end stress and the axial displacement of the fracture end are compare under the axial stress load.GroupⅢis dorsiflexion type of which plate and screws system inⅢ_Aand hollow screws system inⅢ_B.When the ankle model is in neutral position,Ⅲ_A<Ⅲ_B.When the ankle model is 15degrees dorsiflexion,Ⅲ_A1<Ⅲ_B1.When the ankle model is 15 degrees outside,Ⅲ_A2<Ⅲ_B2.GroupⅣis plantarflexion type of which plate and screws system inⅣ_Aand hollow screws system inⅣ_B.When the ankle model is in neutral position,Ⅳ_A<Ⅳ_B.When the ankle model is 15degrees dorsiflexion,Ⅳ_A1<Ⅳ_B1.When the ankle model is 15 degrees plantarflexion,Ⅳ_A2<Ⅳ_B2.Internal fixation maximum stress is compare under the axial stress load.GroupⅢis dorsiflexion type of which plate and screws system inⅢ_Aand hollow screws system inⅢ_B.When the ankle model is in neutral position,Ⅲ_A>Ⅲ_B.When the ankle model is 15degrees dorsiflexion,Ⅲ_A1>Ⅲ_B1.When the ankle model is 15 degrees outside,Ⅲ_A2>Ⅲ_B2.GroupⅣis plantarflexion type of which plate and screws system inⅣ_Aand hollow screws system inⅣ_B.When the ankle model is in neutral position,Ⅳ_A>Ⅳ_B.When the ankle model is 15degrees dorsiflexion,Ⅳ_A1>Ⅳ_B1.When the ankle model is 15 degrees plantarflexion,Ⅳ_A2>Ⅳ_B2.The third chapter:44 patients(15 patients in the varus group with the main support plate in the medial side of the distal tibia,12 patients in the valgus group with the main support plate in the anterolateral side of the distal tibia,8 patients in the dorsiflexion group with the main support plate in the anterolateral side of the distal tibia and 9 patients in the plantarflexion group with the main support plate in the posterior side of the distal tibia.All patients were followed up for 12 to 36 months with an average of 22.5 months.Fractures were obtained by anatomical reduction in 35 cases and general reduction in 9 cases.The fractures were healed from 9 to 21 weeks after operation with an average of 15.5weeks.Patients were given ankle function scores at follow-up.At 12months postoperatively,the average AOFAS of the varus group was88.0 points,the average 83.0 points in the valgus group,the average85.5 points in the dorsiflexion group and the average 90.5 in the plantarflexion group.The good rate in the varus group was 93.33%,in the valgus group was 90.91%,in the dorsiflexion group was 91.67%,in the plantarflexion group was 88.89%,and the average good rate was93.18%.In the control group（AO/OTA classification）,40 patients（12 in43B and 28 in 43C）were followed up for 9 to 33 months（average 20.5months）.Anatomical reduction was obtained in 29 cases,10 cases were generally reduced,and 1 case was worse.The fractures were healed from 12 to 24 weeks after operation with an average of 18.5weeks.Patients were given ankle function scores at follow-up.At 12months postoperatively,the average AOFAS score of the 43B type was87.5 points,and the 43C type was 81.0 points.The excellent and good rate of 43B type was 91.67%,the 43C type was 89.29%,and the average was 94.06%.Comparison of the incidence of complications in the two groups,experimental group was lower than the control group,the difference was statistically significant（p<0.05）.The quality and function of fracture reduction were compared between the two groups.The excellent rate and AOFAS score in the experimental group were higher than those in the control group.The difference was statistically significant（p<0.05）.Conclusion The results of the study shows that,the internal fixation concept proposed by comprehensive classification of tibial Pilon fracture which different internal fixation methods should be adopted according to different types and the main support plate is applied to against the combined force of vertical stress and torsional stress has a reliable mechanical basis.The main support plate is applied to resist the vertical and torsional stress forces to reduce the failure rate of internal fixation.Finite element experiments showed that the main support plate of varus type internal fixation was superior to the anterolateral placement plate in stability of the medial,and the main support plate of the valgus internal fixation was superior to the medial plate in stability of the anterolateral;The selection of plate and screw fixation system for the main support internal fixation of the dorsiflexion and plantarflexion type are superior to the hollow screw internal fixation system.The clinical observation of tibial Pilon fracture with comprehensive classification is satisfactory,and the finite element experiments further confirm the conclusions of the clinical observation study,which provides a biomechanical basis for the comprehensive clinical application of the tibial Pilon fracture which can guide the surgical approach,fracture reduction and placement of the main support plate.The tibial Pilon fracture and the Comprehensive classification are the unity of whole and part.The proposition of Comprehensive classification is in line with the basic principle of“holism concept and syndrome differentiation”in traditional Chinese medicine,which fully explains the essence of the combination of Chinese and Western medicine.