| With the enhancement of the concept of Health Science and technology progress and the crowd traffic industry, fractures in foot and ankle have become a common clinical disease. The ankle joint is the coordination of human walking, running and jumping and other daily activities all need the involvement of the ankle, ankle joint is the most vulnerable to one of the joint injury. Calcaneal fractures account for 2% of all fractures and occurs most commonly in collision accidents or falling from a height. Calcaneal fractures always share a character of mostly intra-articular and complicated conditions because of the unique complex anatomy of calcaneus with many different joint orientations. To classify the complicated calcaneal fractures, the Sanders typing based on the fracture line(s) in posterior facet (type I, none-displaced; type Ⅱ, displaced with 2 fragments; type Ⅲ, three major fracture fragments; type IV, comminuted) is currently widely used. It could help evaluate the prognosis through this CT scanning-based classification is judged limited to the posterior facet. Calcaneal fractures of Sanders type I can often be treated non-operatively with success, while the patients with calcaneal fractures of Sanders type Ⅳ always be treated with a unsatisfied outcomes,2 or even suggested non-operated. The proper management of fixation in calcaneal fractures of Sanders type Ⅱ and type Ⅲ is vital to the prognosis, which remains controversial. More researches are needed to help solve the optical fixation problems of fixation in Sanders type II and type III calcaneal fractures.Open reduction and internal fixation (ORIF) is viewed as the best method, or even "gold standard" to treat complex displaced intra-articular fractures, especially for Sanders type Ⅱ and type Ⅲ calcaneal fractures, which is the focus of researches. With the development of internal and external fixation technology and minimally invasive plating method, the more plentiful alternative surgical managing was in reality than before, but subtalar joint stiffness still existed mostly. However, satisfactory prognostic outcome always acquired by restoration of normal calcaneus anatomy (the joint, calcaneus height and length), were always benefited from ORIF. So far, the fixation techniques have been widely published but still controversial regarding the locking plating, non-locking plating and minimally invasive plating method.10 the mini-invasive plating system was introduced widely as the enough achieving of reduction with less loss of surrounding tissue. When considering the fixation, the soft-tissue which could decide whether ORIF is accepted, and the approaches (extended lateral approach and tarsal sinus approach etc), both are vital factors to determine the surgical plan. Apart with these factors, the stability acquired by different fixations should be considered, because the instability could potentially lead to complications as nonunion or infection. The comparing of fixation stability could help guide the high-valued and controversial calcaneal fractures treatment, which directly affects the functional outcomes of patients.The computational finite element analysis (FEA) provides a reliable method to describe the possible change of displacement or press under various loading. The impractical conditions could be simulated close to reality, which has been clarified as the excellent agreement with reality experimented by the validation study of ankle. After constructing three-dimensional (3D) models and the complex behavior of calcaneus restricted, the displacement, stress, and deformation were directly identified by finite element analysis conveniently. In this study, the method of finite element analysis was used to compare the biomechanical stability of minimally invasive, locking and non-locking plating systems in fixing calcaneal fractures in Sanders type II and type III.Open reduction and internal fixation (ORIF) is the treatment of complicated displaced intra-articular calcaneal fractures "gold standard", especially for Sanders types Ⅱ and Ⅲ type of calcaneal fractures, focus is the scientific study of the same ORIF. With the development of internal, external fixation technique and minimally invasive plate and other internal fixation devices, calcaneal fracture operation mode has more options and the operation effect is improved obviously, but the subtalar joint stiffness and other complications still exist. If the open reduction and internal fixation of calcaneal anatomic reduction degree of recovery (e.g., calcaneus, calcaneal height and length) satisfaction, prognostic and good results. At present, more research about fixation technology calcaneus, but for locking plate, non locking nail plate and reduce the specific use of minimally invasive plate fixation system surrounding soft tissue injury, there are still disputes. An important factor in determining the operation scheme including soft tissue conditions (to decide whether to accept the open reduction and internal fixation) and operation approach (enlarged lateral approach and tarsal sinus approach) etc.. In addition to these factors, we should consider the stability of internal fixation with different gain, because of unstable fracture may lead to nonunion or complications such as infection. Comparison helps to choose appropriate treatment for the fixed stability, directly influence the functional outcome in patients with.Finite element analysis of computer technology can accurately describe the various stress change, simulation of various boundary conditions, can simulate the fracture line displacement degree more real reliable end or stress. For example, the finite element three-dimensional reconstruction of ankle and calcaneal, many related literatures have confirmed its three-dimensional (3D) model’s accuracy and reliability, and can be conveniently analyzed by finite element simulation of complex displacement, stress and deformation. This study adopts the method of finite element analysis, comparison of minimally invasive fixation system, nail locking and non locking nail plate system fixed biomechanical stability of Sanders type II and type III fracture of calcaneus.Objective1, select a male volunteers ankle CT raw data, the initial establishment of 3D model of foot and ankle were reconstructed after the establishment of finite element model, model selection of calcaneus treated, and according to the Sanders classification to establish Sanders Ⅱ type and Sanders Ⅲ type calcaneal fracture finite element model, and 3D scanning related operation instrument. This part mainly discusses the method of building 3D model of three dimensional finite element model of the calcaneus and Sanders Ⅱ type and Sanders Ⅲ type calcaneal with accurate anatomic structures and ligament structure fracture and related internal fixation using Mimics, Geomagic, SolidWorks, ANSYS and other software.2, Validation of the established ankle three-dimensional finite element model, the three-dimensional finite element model of calcaneus. To establish the three-dimensional model of the normal ankle joint in neutral position, the applied load (simulating human body static neutral single foot standing weight-bearing state), simulated neutral position of ankle joint surface stress distribution and contact area, and combining with the relevant literature on the effectiveness of the results is verified. On calcaneus in 3D reverse software on the anatomic parameters measured, and compared with the normal anatomic parameters of calcaneus, proves the real form of reliability.3, according to the Sanders Ⅱ type and Sanders type Ⅲ fractures of the calcaneus the established finite element model type, are simulated respectively into the lock the nail steel plate and non locking plate system. The evaluation in accordance with the relevant literature of internal fixation and fracture stability index, in the calcaneus stress loading, comparative analysis of locking plate and non locking plate fixation of calcaneal fracture model under the use of the finite element analysis method. Analysis of displacement, relative displacement of fracture line, plate and screw fixation system and fracture stress distribution. Discussion of Sanders Ⅱ type and Sanders type Ⅲ fractures of the calcaneus locking nail plate and non stability effect of locking plate fixation after calcaneal fracture system.4, Effectiveness evaluation of Sanders Ⅱ fixed type and Sanders Ⅲ type calcaneal fractures with less invasive stabilization system, analysis of displacement, relative displacement, fracture line plate and screw fixation system and fracture stress distribution, and with the locking plate and non locking plate system stability index contrast to each other to fix the fracture of calcaneus. Objective to compare and minimally invasive plate fixation of Sanders Ⅱ type and Sanders type Ⅲ fractures of the calcaneus fracture stability.Methods1, Establishment of three-dimensional finite element digital model. Sanders Ⅱ type and Sanders type Ⅲ fracture of calcaneus:first establish the finite element model of the ankle and foot, that is, by a male volunteers (24 years old, height 178cm, weight 70kg), in the radiology department of Nanfang Hospital of Southern Medical University for foot and ankle CT plain scan, obtain the ankle CT raw data in Dicom format. The specific scanning parameters using 64 slice spiral CT imaging,120-140, voltage KV, current intensity of 240-300 mA, get the Dicom format data of 512* 512 matrix. Volunteers ankle to keep a neutral position, scan range from above the ankle plantar downward scan to. After scanning the original data input 3D reconstruction software Mimics 11, select the automatic threshold segmentation according to manually modify the related anatomical drawing parameter threshold, namely 3D reconstruction of 3D models of foot and ankle bone integrity. After importing the Geomagic software within the triangle modification and point cloud processing, which makes the model more smooth. The final input into SolidWorks software in geometric model generation and reconstruction of assembly, and imported into the finite element analysis software ANSYS software, mechanical and other soft tissue structures surrounding ligament reconstruction. According to the Ⅱ type and Ⅲ type calcaneal Sanders typing of fracture characteristics, cutting production related fracture model in SolidWorks software.2, Validation of a three-dimensional finite element model of ankle fracture of calcaneus:for the foot and ankle model has been established, including the ankle and calcaneus model model, finite element analysis is carried out to verify and calcaneal morphology to verify its effectiveness. Validation of the established ankle ankle three-dimensional finite element model, the three-dimensional finite element model of calcaneus. To establish the three-dimensional model of normal ankle joint, in the ANSYS software simulation to add 8 ankle ligament, pre tension of ligament under zero load design for the shortened 2%, bone and ligament are used with linear model to the homogeneous, and set the specific material properties. Applying neutral load (simulating human body static neutral single foot standing weight-bearing state), using the finite element software ANSYS analysis technique to measure the neutral position in ankle joint surface stress distribution and contact area, and combining with the relevant literature on the effectiveness of the result of verification. For in a three-dimensional reverse software such as former minister, calcaneal anatomical calcaneal height and width, length, level of calcaneus sustentaculum long, wide, high, wide, high and calcaneal thalamus bottom length parameter measuring, and the anatomic parameters of the related literature compared with normal calcaneus, proves the form the true reliability.3, non locking plate and a locking nail fixation of Sanders type Ⅱ plate and Sanders III type calcaneal fracture finite element mechanical stability analysis and comparison:3D scanning related operation instruments such as locking and Y type non relevant sizes of locking plate, at the same time scan matching with screws on a personal computer, after admiral 3D data summary. In the setting of SolidWorks steel plate screw internal fixation material smooth, can be directly used for the simulation of fixed fracture model. Titanium plate and titanium screw material is the selection of Young’s modulus and Poisson’s ratio is 0.33 106000mpa. According to the clinical operation technology will all internal fixator placed on the lateral calcaneus, cortical bone screw all access, avoid the other side throughout the cortical bone or joint surface. Analysis of main indicators for the stability of fracture (fracture displacement extent reflected by), internal fixation system and internal fixation bone around three aspects to the fixed effect of stress distribution of fixed assessment in. Set the X axis (the ankle point inward), Y axis (toes pointing to the heel, XY plane parallel to the plane of the Z axis (foot), heel toward the knee), further calculation fracture displacement in three-dimensional coordinates of the. Through the finite element analysis method, recording the different internal fixation methods of fracture block under maximum degree of displacement, internal fixation and bone peak stress and stress distribution.4, minimally invasive locking nail mechanics finite element analysis of the stability of type Ⅱ fixed Sanders plate and Sanders Ⅲ type calcaneal fracture at. Minimally invasive internal fixation steel plate small calcaneus calcaneal minimally invasive plate (Medical Instrument Co., Ltd, Jiangsu Province, Chinese), fixed method using the laminating lateral calcaneal all into cortical bone screw and screw, with or without the two screws from the calcaneal tuberosity diameter 5.5mm into the calcaneocuboid articulation. Through the analysis of main indicators for the stability of fracture, internal fixation system and internal fixation bone around three aspects should be stress distribution, to explore the effect of minimally invasive plate fixation (simple minimally invasive plate fixation or minimally invasive plate fixation combined with cortical screws two gold rear diameter 5.5mm from the node at the calcaneus into the calcaneocuboid articulation).Results1, Establishment of three-dimensional finite element digital model. Sanders Ⅱ type and Sanders type Ⅲ fracture of calcaneus:ankle CT data based on a male volunteers, successful reconstruction of 3D model of foot and ankle, complete bony structure into Geomagic software within the triangle modification and point cloud processing, import the SolidWorks software in construction of foot and ankle ligament assembly different skeletal structure model, ANSYS software. According to the Ⅱ type and Ⅲ type calcaneal Sanders typing of fracture characteristics, formation of Sanders Ⅱ cutting type and Sanders Ⅲ type calcaneal fracture model in SolidWorks software.2, Validation of a three-dimensional finite element model of ankle fracture of calcaneus:established the finite element model of the ankle ministry were related verification. For ankle joint model part, add 8 ankle ligament, pre tension of ligament under zero load design for the shortened 2%, bone and ligament are used to the same homogeneous linear model. Applying the 600N stress in the ankle joint model of the neutral position, at this time the articular contact area is 405mm2, the maximum contact stress is 4.5MPa, the contact area is close to the relevant literature, the stress distribution and the true stress conditions similar to the articular surface of the tibia. For the calcaneus model part, has carried on the related anatomic parameter measurement, calcaneal length is 64.80 mm, width of anterior calcaneus, calcaneal sulcus width, the width of the posterior calcaneus were 20.4 mm,1 mm and 31 mm, and the normal calcaneal anatomic parameters related literature contrast similar. Through the measurement of the calcaneus posterior articular surface area, its value is close and related documents. The above results preliminarily proved that the model of the real form of reliability. Sanders Ⅱ type and Sanders Ⅲ type calcaneal fracture internal fixation of further analysis showed, the fracture line displacement, stress and plate screw internal fixation stress in the reasonable range of fracture, three dimensional model shows reasonable reliability.3, non locking plate and a locking nail fixation of Sanders type Ⅱ plate and Sanders Ⅲ type calcaneal fracture finite element mechanical stability analysis and comparison for model Sanders:IIA type and Sanders type ⅡB fractures of the calcaneus, degree of displacement and the relative displacement of the fracture line degree results show that locking nail steel plate fixation is superior to that of non locking plate (fracture Sanders type ⅡA locking plate group, fracture line shift:1 micron, non locking plate group, fracture line shift:3 microns; Sanders type ⅡB locking plate group, fracture line shift:1.7 micron, non locking plate group, fracture line shift:5 m), Sanders ⅡC type of calcaneal fractures and two similar shift model. For the Sanders ⅡA type, B type and C type calcaneal fractures, non locking nail plate internal fixation group the peak stress is higher than locking plate group, calcaneal locking nail plate group peak stress was higher than that of the non locking plate group, but were located in the reasonable range. Prompt locking plate fixation compared with non locking plate is more stable, calcaneal stress than non locking plate group, rather than locking plate group is fixed, the more stress concentrated in the fixture. Non locking plate and locking plate internal fixation of calcaneal stress and the stress distribution has no obvious concentration phenomenon, in front of the stress distribution of larger calcaneal plate. For the model of Sanders Ⅲ AB type, BC type and AC type calcaneal fractures, degree of displacement and the relative displacement of the fracture line degree showed locking plate fixation group and non locking plate group values are relatively close to the fracture, no obvious difference. Locking plate fixation compared with non locking plate, calcaneal stress is close to but greater than non locking plate group, rather than locking plate group is fixed, concentrated in the peak stress more fixture. Non locking plate and locking plate internal fixation of calcaneal stress and the stress distribution has no obvious concentration phenomenon, in front of the stress distribution of larger calcaneal plate.4, minimally invasive locking nail mechanics finite element analysis of the stability of type Ⅱ fixed Sanders plate and Sanders Ⅲ type calcaneal fracture at. Fixed Sanders Ⅱ type calcaneal fractures, minimally invasive locking plate with or without the two medals from back to front fixed screws can reach the appropriate mechanical stability. Among them, the minimally invasive locking nail plate with screw group, better stability, and sometimes even better than the non locking plate group and the locking plate group (except for Sanders type ⅡB fractures of the calcaneus), minimally invasive plate fixation and internal fixation of calcaneal when stress and stress distribution were not significantly concentrated in the central phenomenon, minimally invasive calcaneal plate stress distribution is large. Fixed Sanders Ⅲ type calcaneal fractures, minimally invasive locking plate with or without the two medals from back to front fixed screw can also achieve the mechanical stability of the right, and minimally invasive locking plate with screw group has better stability, minimally invasive plate fixation and internal fixation of calcaneal when stress and stress distribution were not significantly concentrated in the central phenomenon, minimally invasive the stress distribution of larger calcaneal plate. The above results suggest that minimally invasive locking plate can be applied to a fixed Sanders Ⅱ type and Sanders Ⅲ type calcaneal fracture mechanics, has good stability, and the calcaneus plate with backwards through the fixing screw is better than that of simple minimally invasive calcaneal plate.Conclusion1, based on the more easily constructed three-dimensional finite element model of the ankle and foot ankle volunteer CT data, and has better simulation and can simulate the mechanical condition is relatively complex.2, The locking plate stability only in Sanders Ⅱ type calcaneal fracture model is better than the non locking plate in the model, and the difference between the two Sanders Ⅲ type calcaneal fractures are not obvious.3, calcaneus plate fixation system has better mechanical stability and stress distribution feature, the calcaneus plate with backwards through the fixing screw is better than that of simple minimally invasive calcaneal plate. |
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