The Establishment And Significance Of Standard Parts Library Of Proximal Tibia Plates Based On Reverse Engineering

BackgroundTibial plateau fractures are common intra-articular fractures in the clinical, as a weight-bearing structure of the knee, its treatment and prognosis will produce very big effect on knee joint function. Non-surgical treatment is suitable for a small number of patients which are incomplete or non-displaced fractures or can not perform surgery. Due to non-surgical treatment fixed a long time, late functional recovery exercise and the unability to achieve anatomic reduction and other factors, those may will lead to a series of complications, such as joint stiffness, deformity and long-term traumatic arthritis. For most patients, surgery is the preferred treatment of such fractures, and open reduction and internal fixation of the treatment is the main means. Appropriate internal fixation will maintain the integrity of the articular surface after reduction. Early functional exercise actively will effectively improve joint strength and activity, prevent muscle atrophy and joint stiffness, and promote the recovery of knee function.On the basis of the common treatment of the internal fixation, considering the patient’s condition, individual differences and economic conditions, that will design a reasonable surgical options. However, the skeletal morphology of human varies from person to person, such as age, sex, race, occupation and other individual differences. This means that the current fixation implant products largely cannot fully meet everyone’s needs. Such differences are more prominent that in the case of normal bone anatomical position change or bone loss. And the internal fixation implants not only to ensure a perfect match with the bone contour after reduction, but also to ensure that critical fracture fixation block to maintain the integrity of the articular surface and reset lines of force of the knee joint stability. Compared to the fixation of surgical approach and surgical options, the rationality of the implant fixation applications often been overlooked by doctors. Although, the internal fixation devices businesses have provided diversity of their choice, to some extent, this phenomenon meets the need of such individual differences, but these abundant resources were not good to be used by the medical industry, and this phenomenon is more pronounced in the prefecture-level hospital. Due to affordability of the patient and regional differences of medical resources, hospitals tender fixation implants are often limited to a few, or even a single production industry, the scope of the choice of fixation implants is very small even no bearing appears suitable choice, under these circumstances, the effect of unreasonable implantation often is unsatisfactory.With the development of digital orthopaedics and digital computer aided technology, we can perform the design of personalized internal fixation, virtual surgical operation and intra-operative navigation, etc. Compared with the traditional empirical treatment of orthopedics operation, it is more reasonable, personalized and precise and meets the modern trend of orthopedic. According to relevant clinical studies reported that personalized design, with the help of CAD software, has got a custom fit with illness fixation implants by rapid prototyping technology and obtained the desired shape to ensure an accurately match with the diseased region. Although, the individually designed internal fixation implants has considerablely met the bone contour, as a medical product, especially the invasive surgical instrument, the safety and function of the new production should be be further confirmed an well as its mechanical properties and should be met the international standards. Another literature reports that through the 3D to print out fracture model and then simulated the process of fracture reduction, and reshaped the internal fixation plate on the base of the original products. It also achieves the personalized treatment, what’s more, and has saved surgery time. However, it will has an unpredictable effect on mechanical properties of the original structure after the process of plate prebending. Early domestic scholar has proposed the concept of digital plates contained digital model and function model. The digital model of plate will could lead to virtual simulation operation, on the other hand, and the function model of plate,by finite element analysis, will help compare the effect of implantation of different ways of operation and forecast the feasibility of operation. But the researcher doesn’t go further study.There is a certain distance from personalized fixation implants, the more feasible is what concerns the hands of the rational use of resources and how to achieve personal purposes, and this personalization options are established on diversity fixed implant resource, which covers all or mainstream production industry. What’s more, internal fixation implants are an essential factor in virtual simulation surgery, and specifications complete fixation implant model is undoubtedly conducive to the digital design optimization of fracture operation, and provides the function evaluation of individualized treatment of complex fractures.ObjectiveEstablishing the digital model library of proximal tibia plates which cover all or mainstream production industry to provide the basis for the simulation operation of the digital orthopaedics meet personalized selection in diversity resources. To explore the modeling method of finite element model of plate and then provide convenience for clinical diagnosis and treatment analysis of biomechanics.MaterialsProximal tibial plate total 186 (Synthes, Jema, Watson, Wei Gao, Double, Stryker). Operating System:Dell T7500(Windows 7 Ultimate 64bit, Intel Xeon 5600, CPU Clock Speed:2.93GHz, The graphics chip:NVIDIA Quadro NVS295), Dell M6600(Windows 7 Ultimate 64bit, Intel Core i7, CPU Clock Speed:2.5GHz, The graphics chip:NVIDIA Quadro NVS 4000M), Medical three-dimensional reconstruction software:Mimics 14.0(Materialise Corp, Belgium), Reverse engineering software:Geomagic 12.0(Raindrop Geomagic Corp, USA); Finite element analysis software:Ansysl3.0(Ansys Corp, USA).This study is divided into two parts:1.To explore the construction of the high simulation proximal tibial plate digital model library, including without nails and nail; 2.To discuss the modeling method of finite element model of plate in fast and high simulation.Methods1. Establish a high simulation proximal tibial plate digital model library1.1 Thin-section CT scans and three-dimensional reconstructionThe proximal tibia plates were fixed on cardboard, the size of 30*10cm 3 layer, with medical adhesive plaster.Meanwhile, scan a plate with nails to adapt to the other production. Scan specific parameters:pitch 0.3mm, current 100mAs, voltage 120kv, The data was saved in DICOM format,then burned a DVD disc. The data of sectional images was processed and edited by Mimics software, including Thresholding, region growing, three-dimensional reconstruction.1.2 Morphological processingThe 3D models were imported into Geomagic 2012 software After three-dimensional reconstruction and had been performed morphological processing, Depending on the quality of the model, we can take actions such as:grid doctor, quickly smoothing, noise reduction, the removal of features, sandpaper,etc.1.3 Volume recoveryIn Mimics by "Rescale" module, check the "Keep Originals" and "Uniform", the Geomagic treated with volume ratio of the original model as the cube root of the volume coefficient of restitution, and enter in "Factor" to make the volume recovery,and then complete construction of the proximal tibial plate digital model library without nail.1.4 Build with proximal tibial plate with nail digital model libraryThrough "MedCAD" draw a cylinder diameter of 2.2mm screw channel in Mimics, and simulate real-screw direction in the real nail reference.Then with the nail plate as a reference, adjust the position by "Reposition", perform "Union" between the simulation channel of nails and the corresponding plate. And then complete construction of the proximal tibial plate digital model library with nail.1.5 Statistical analysisStatistical analysis was performed with SPSS 20.0 software. Comparison of performance between volume, surface and triangulars was undertaken using the One-way analyses of variance (ANOVA). P<0.05 was considered statistically significant.2 Establish finite element model of proximal tibial plate2.1 Surface meshingAccording to the above step in 3D reconstruction, morphology optimization, set the "Target Edge Length" parameter in "Remesh".The software automatically will give default values, in order to optimize the subsequent calculations, the need to explore the deformation as small as possible under the premise of optimizing computational side of the goal setting. With 0.2mm intervals set 0.7mm to 2.1mm total 8 groups, record the number of triangles, surface area, volume. Preform volume recovery laterly.2.2 Volume meshingUsing Ansys stream file the command form of complete meshing. Specific steps include:(1) specify the working directory:ease of management, the file output is concentrated in the fixation of the implant to the named folder, the file name can not appear in Chinese characters attention; (2) reads the command stream file; (3) follow the prompts to enter the three-dimensional model of Ansys Elements format output Lis, Nodes and Element format. This step is carried out by Ansys check mesh quality can meet the minimum requirements for finite element analysis, successful completion of this step can be finalized finite element modeling.2.3 Assign the material propertiesComplete meshing using Ansys command stream. The concrete steps include:(1) Confirm the working directory for convenient operation.The file name should pay attention to not appear Chinese characters and special characters; (2)Read command flow document; (3) According to the cue input 3D model in the Ansys Elements file format, and the output file in Lis, Nodes and Element format. This process will be to verify the quality of grid. And practice has proved that it can finally complete finite element modeling if this process complete successfully.Results1. Establish a total of 186 proximal tibial plate digital model libraries from six production industrys;2. After Geomagic morphological optimize treatment, the ANOVA of the volume and the surface area of the original model and processing model is P>0.05, this prompt that Geomagic repair model in appearance, while the volume did not change significantly. Comparison of the original model after triangular facets and Geomagic treatment, P<0.05, show appearance has been repaired. Comparing the data after Mimics recovery volume, the surface area of comparative P>0.05, shows that the change is only the volume, but the appearance has not changed, indicating that the recovery does not affect the standard volume level simulation.Morphology optimization in Geomagic and volume recovery in Mimics can make the 3D model of plate have high simulation degree;3.It can reconstruct the accurately geometry model based on date of thin-section CT images, which can meet the need of finite element modeling; It simplifys the operation process and improves the efficiency of finite element modeling by Ansys command stream.Conclusion1. Based on CT scan data, through reverse engineering software can achieve accurately standard parts library of the proximal tibia plate;2. The standard parts library of digital model is suitable for virtual operation design in orthopedics;3. Command flow can perform finite element modeling fastly, which will help solve the problem related to finite element modeling of complicated equipment.