Data Modeling And Application Research Of 3d-printed Orthopedic Cast For Forearm

BACKGROUNDIn recent years,3D printing technology has been developing rapidly.It is widely used in the manuf-acture of complex physical models,providing effective solutions for fast and accurate personalized manufacturing,and has received great attention in various fields of the world.In the medical field,due to its individualized manufacturing characteristics,3D printing technique has made remarkable breakthroughs,especially in surgical assistance,personalized prosthesis implantation and clinical training.The effect has also been recognized gradually in clinical.The 3D printing of medicine starts from the experimental stage to clinical application.Among them,3D printed personalized cast is an important aspect of the clinical application.With the improvement of people's requirements for medical quality,personalized rehabilitation auxiliary equipment is more and more popular.It not only requires a higher clinical effect,but also puts forward higher requirements in terms of comfort and appearance.At present,the 3D-printed orthopedic cast has become the most promising solution.In the process of medical 3D printing,if the computer performs 3D simulation design on the human body structure,it needs to obtain three-dimensional data of the corresponding parts or organs of the human body at first,thereby realizing individualized design for the patient.To achieve the personalized external fixation for treatment,we need to collect the three-dimensional patient's extremity data before printing 3D personal cast.However,the process steps from data acquisition,computer modeling,design to printing are complex,which requires multi-disciplinary to achieve an individualized cast in the 3D printing process.It greatly limits the de,velopment and clinical application of the technology.In order to overcome this difficulty.data collection and modeling desi5gn should be optimized.In aspects of data acquisition,magnetic resonance scanming has high tissue resolution and no ionizing radiation,which has great potential in human data acquisition.However,the magnetic resonance imaging principle is complicated and most sequences are designed for clinical diagnosis purposes,there are many restrictions on the application of 3D printing.If we want to apply magnetic resonance to acquire the three-dimensional geometric data of limbs,we must optimize the sequence and parameters to achieve accurate,fast three-dimensional acquisition.In tenms of modeling design,a modeling system is targeted for designing a 3D printed cast easier to use and ensuring the clinical effect.Therefore,it must standardize each step in the process.In addition,the research on digitization and quantification of the cast 1s to solve the problems of complex modeling and over-specialized in printing processes.Furthermore,the research on the clinical application of 3D printed personalized external fixation 1s rare and research data on clinical actual cases is still lacking.The mechanical analysis of the 3D-printed orthopedic cast for protecting limbs also requires more experimental data for verification.OBJECTIVEThe objective of this study is to explore the practical application of medical 3D printing.In order to meet the requirements of 3D data acquisition for 3D printing design cast,the magnetic resonance rapid imaging sequence is selected for optimizing to provide a simple and effective alternative data acquisition for human body surface.By developing a patient-specific rapid modeling intelligent system.the clinical application of this system in the treatment distal radius fractures is studied.This will provide a new idea and solution for the treatment of orthopedic external fixation.METHODS1.The magnetic resonance rapid imaging sequence was screened.The relevant parameters were optimized.Then the parameter settings were analyzed and validated by specific scanning experiments.According to the data requirements of the 3D-printed cast,the spoiler gradient echo sequence was selected and combined with the modified DIXON technology to optimize the scanning parameters.The parallel acquisition technology was used to shorten the scanning time.The relationship between image resolution,scan time,and signal-to-noise ratio was compared and analyzed.The spoiler gradient echo and parallel acquisition techniques were tested and optimized the forearm 3D data acquisition by using the 3.0-T MRI units(Discovery,750w,GE,USA).The mDIXON-FFE sequence was optimized volunteer foreamm scanning parameters and data acquisition by using the 3.0-T MRI units(Aceieva,Netherlands,Philips)2.For the practical application process of 3D printing technology in the extremity cast,the modeling design process was decomposed into the following steps:develops a basic model from image-based patient data,computes geometric reference of cast data,models flare edges,builds cast surface pattern,creates a solid model of the cast.Rapid model designing system software was developed by using Visualization Toolkit(VTK Kitware).Sixty patients were involved in this study.These patients were suffered from forearm fractures and treated with manual reduction and extenlal fixation cast.They were divided into 3D-printed external cast group,traditional plaster external fixation group and splint external fixation group,with 20 patients in each group.The clinical efficacy and patient satisfaction were compared.3.The three-dimensional solid model of the normal forearm wearing a 3D-printed cast was established.The solid cast model of the distal ulnar fracture was made by manual segnmentation of the distal ulnar bone.Using the Geomagic software for reverse engineering reconstruction,and the Solidworks software is used to model and assemble according to the cast drawings to obtain a complete geometric model.Then it was imported into ANSYS Workbench software to divide the three-dimensional finite element mesh to obtain the 3D finite element model f-or calculation.The fixed constraint of the full-degree freedom on the proximal radial and ulna was set.The ultimate load of the palm was set as 400N in different directions and IN/m in rotating inside or outside,then the stress distribution and fracture displacement under different working conditions were observed.RESULTS1.Under the premise of isotropic scanning,with the increasing of voxels,the scanning time was shortened,the spatial resolution of the image was reduced,the tissue contrast was decreased,the tissue level was blurred,and the surface physiological marker structure was gradually ambiguous.The increasing of parallel acquisition acceleration factor influences the image signal-to-noise ratio,but the imaging speed was significantly shortened.Parallel acquisition technology was the most important factor to shorten the scan time within the acceptable range of resolution.The mDIXON-FFE sequence was used for 3D data acquisition of the forearm to obtain the 3D geometric information of the limb.At the same time,the image reconstruction with different contrast can be performed.The average time of the three-dimensional scanning of the forearam was optimized in 34 seconds by the setting of the scainning parameters.2.The rapid automatic modeling systerIm can be completed on the computer by several steps of lodelinIg and designing the external cast.After familiarizing with the operation steps,a clinical staff with basic computer operation ability could create a cast of about 20 minutes.In the condition of ultimate load,the deformation of the cast arnd limbs is different uncder six different working conditions,and the displacement of the fracture end is different under different working conditions.the fracture displacements the four compression directions from anterior-posterior,posterior-anterior.medial to lateral,lateral to medial were 1.2648,1.3253.0.8503,and 0.8957(mm),respectively.And the corresponding fracture stresses were 4.5986,3.9129,and 5.0334,7.9197(MPa),respectively.The internal and external rotation fracture displacement were 0.02628 and 0.02628(numm),respectively.The fracture surface stresses were 0.1733 and 0.1723(MPa),respectively.3.In the evaluation of external fixation treatment,the scores of group A,B and C were 10.20±0.951,9.10±1.119 and 9.35±1.137 respectively.Among the patients with blood and pressure ulcer assessment,the score of group A was higher than group B and C(the difference was statistically significant).In the evaluation of patient satisfaction.,the scores of group A,B and C were 8.65±1.040,6.85±1.137 and 8.10±1.252 respectively.Patients in group A scored higher than those in group B and C in terms of comfort,smell and skin sensation(the difference was statistically significant).CONCLUSIONS1.Through sequence screening and optimization,spoiler gradient echo and parallel imaging technology can be used as a fast 3D scan sequence for extremity information acquisition.They can be provided accurate 3D geometric information for 3D-printed external fixation and more options for 3D extremity information acquisition.2.The 3D-printed cast rapid modeling system based on extremity surface information can be modularized,stepped and standardized the printing process.This system can be used as a clinical promotion method for the 3D-printed cast.3.In the treatment of forearm fracture,the 3D-printed cast has a good clinical effect and patient satisfaction.It can be used as one of the options for the clinical treatment of external fixation.