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    Editorial
    Medical Application of 3D Printing:A Powerful Tool for Personalised Treatment
    DAI Kerong (戴尅戎), XU Feng (许锋)
    2021, 26 (3):  257-258.  doi: 10.1007/s12204-021-2290-8
    Abstract ( 450 )   PDF (86KB) ( 188 )  
    We are in an era of technological revolutions promoting personalised healthcare. Advances in medical imaging techniques with 3D imaging software and 3D printing have allowed healthcare professionals to view and document various geometrical structures in a brand-new way, enabling them to make meaningful 3D measurements more accurately by generating both virtual and physical models used for preoperative planning,physician-patient communication, and fabrication of surgical guides, instruments, and implants[1-5]. With improvements in cost-effectiveness, efficiency, and mechanical properties, 3D printing technologies have become a powerful tool for physicians to meet clinical requirements. Furthermore, biological tissues made from 3D printing may eventually provide patients with required human organs in the future[6-7].
    Although both medical communities and socialmedia spare no effort to highlight the prospects of 3D printing technologies in healthcare and popularise this innovative new method through Web-based approaches to promote its application in personalised treatment, to date, not a single healthcare organisation has yet released new technologies, disseminated findings in peerreviewed
    literature, or clarified the role and aims of 3D printing in healthcare. This, in turn, has left much of the current research and development to medical device companies, expecting them to meet individual clinical requests. Therefore, at present and in the future, it is critical to have a clear understanding of the clinical implementation of 3D printing for both traditional and personalised healthcare.
    The first step in the entire 3D printing process starts with medical imaging, in which professionals with expertise
    in radiology and imaging processing have conducted many investigations to identify and quantify patient-specific anatomical areas and geometrical structures before designing and manufacturing personalised medical models, surgical guides, medical instruments,
    and devices using 3D printing[8-11]. It must be noted that 3D printing usually starts with conventional clinical images, and errors cannot be avoided with several more complex steps involved in image processing. Traditionally,medical images have been acquired in radiology departments by trained radiologists using special software packages. With the help of commercial medical imaging processing software, such as MIMICS,Analyze, and MeDraw, many physicians from different specialties, with little engineering background, are able to perform these analyses by themselves and develop their preoperative planning software tailored to special
    medical treatments. Understandably, the development of software tailored to 3D printing needed in medicine could accelerate and promote its popularity in clinical practice.
    Organised by Journal of Shanghai Jiao Tong University (Science), this special issue, authored by a group of physicians and engineers with diverse and interdisciplinary backgrounds and insights, is intended to introduce their research topics in the most hotly debated areas where medical 3D printing is used in patient care,especially focusing on medical and dental applications.
    The issue also presents some related topics about imaging generation and processing, material properties, and biomechanics, among others. However, it is difficult to cover all the 3D printing fundamentals.
    In the current special issue, some interesting studies provide details regarding how to apply 3D printing to medical or dental personalised healthcare, which could be invaluable for physicians who would like to find their own methods of developing personalised routines by applying 3D printing in daily practice. The issue also includes some dedicated studies that focus
    on imaging and software applications, which are indispensable for those who are eager to enter the field of pre-processing in 3D printing. Last but not least, some studies discussing material properties and biomechanics with in-depth insights regarding the safety and reliability of 3D printing technology in the manufacturing of medical devices can be found in this issue. As authors
    and advocates of personalised treatment, we are interested in promoting 3D printing from its current niche applications to more widespread use in the medical community. Thus, this special issue also includes studies on some of these niche applications. Since 3D printing technology is now growing at an exponential rate, it is definitely a very challenging task to organise issues on 3D printing in personalised patient care. In this issue, we attempt to inspire our readers by choosing some clinical examples in several representative areas to show how 3D printing positively influences personalised healthcare.
    There is no doubt that 3D printing is truly one of the leading technologies of the 21st century and praised as a key feature of the fourth industrial revolution. We hope this special issue could provide essential information to help you understand the role that 3D printing plays in personalised patient care with the purpose of improving clinical outcomes and quality of life for patients in China and around the world. Finally, we genuinely hope that people with lofty ideals from both medical and engineering fields who are interested in 3D printing technologies notice this special issue and join us to enter the field with your meaningful contributions.
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    Medical 3D Printing and Personalised Medicine
    Biomechanical Analysis of Personalised 3D-Printed Clavicle Plates of Different Materials to Treat Midshaft Clavicle Fractures
    CHENG Rongshan, (程荣山), JIANG Ziang, (蒋子昂), DIMITRIOU Dimitris, GONG Weihua, (龚伟华), TSAI Tsung-Yuan, (蔡宗远)
    2021, 26 (3):  259-266.  doi: 10.1007/s12204-021-2291-7
    Abstract ( 266 )   PDF (1656KB) ( 106 )  
    This study was aimed at comparing the biomechanical performance of personalised 3D-printed clavicle  plates of different materials to treat midshaft clavicle fractures with the finite element (FE) method. The FE  model of a fractured clavicle with a personalised 3D-printed clavicle plate and screws was constructed. Three  types of materials were simulated, including stainless steel, titanium alloy, and magnesium alloy. Two loading  conditions (axial compression and inferior bending) were applied at the distal end of the clavicle to simulate arm  abduction. Plate stiffness, peak stress, and bone strain at the clavicle fracture site were measured and compared.  The stiffness of the stainless steel clavicle plate was significantly greater than that of the titanium alloy clavicle  plate. The stiffness of the magnesium alloy clavicle plate was similar to that of the intact clavicle; peak stress  of the magnesium alloy clavicle plate was the lowest; thus, it had less stress-shielding effects on bone formation.  The magnesium alloy clavicle plate was more likely to form bone by distributing proper strain at the clavicle  fracture site. According to the influence of different materials on the tensile strength, magnesium alloy clavicle  plates might be preferred owing to their bionic stiffness in the treatment of patients with a low risk of falling. For  patients who engage in contact sports, a titanium alloy clavicle plate might be more suitable.
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    3D Printing Bioink Preparation and Application in Cartilage Tissue Reconstruction in Vitro
    SUN Binbin (孙彬彬), HAN Yu (韩煜), JIANG Wenbo (姜闻博), DAI Kerong(戴尅戎)
    2021, 26 (3):  267-271.  doi: 10.1007/s12204-021-2292-6
    Abstract ( 246 )   PDF (1061KB) ( 69 )  
    Three-dimensional (3D) bioprinting technology has great potential for application in the treatment  of cartilage defects. However, the preparation of biocompatible and stable bioinks is still a major challenge. In  this study, decellularized extracellular matrix (dECM) of soft tissue was used as the basic material to prepare the  bioink. Our results showed that this novel dECM-derived bioink had good printing performance and comprised  a large number of fine nanofibers. Biological characterization revealed that the bioink was compatible with the  growth of chondrocytes and that the nanofibrous structure greatly promoted cell proliferation. Histological and  immunohistochemical analyses showed that the in vitro printed cartilage displayed the presence of characteristic  cartilage lacunae. Thus, a new preparation method for dECM-derived bioink with potential application in generation  of cartilage was developed in this study.
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    Research Update on Bioreactors Used in Tissue Engineering
    WANG Wenhao, (王文豪), DENG Qian(邓迁), LI Tao (李涛), LIU Yuehua (刘月华), LIU Yang (刘洋), SUN Yeye (孙叶叶), DENG Changxu (邓昌旭), ZHOU Xiaojun (周小军), MA Zhenjiang (马振江), QIANG Lei (强磊), WANG Jinwu, (王金武), DAI Kerong, (戴尅戎)
    2021, 26 (3):  272-283.  doi: 10.1007/s12204-021-2293-5
    Abstract ( 184 )   PDF (900KB) ( 59 )  
    Owing to the paucity of donor organs and their acute rejection by the immune system after transplantation,  advanced organ failure is one of the major challenges faced by the medical community. Static culturing  used for synthesising tissues and organs cannot simulate the in vivo mechanical and biochemical signals; therefore,  such artificial organs fail to maintain effective functional activity following transplantation. Tissue engineering can  overcome these hurdles by successfully enabling regeneration of tissues and organs in vitro. Bioreactors are pivotal  in the development and generation of engineered biological products. They simulate the in vivo microenvironment  of tissue growth while also providing various mechanical stimuli and biochemical signals to stem cells to effectively  generate transplantable organs or tissues. Various designs and types of bioreactors, their applications, and future  research prospects are summarised, which promote functional tissue engineering.
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    Accuracy Assessment of a Novel Radiographic Method to Evaluate Guided Bone Regeneration Outcomes Using a 3D-Printed Model
    SHI Junyu (史俊宇), LI Yuan (李元), ZHANG Xiao (张枭), ZHANG Xiaomeng (张晓梦), LAI Hongchang (赖红昌)
    2021, 26 (3):  284-289.  doi: 10.1007/s12204-021-2294-4
    Abstract ( 212 )   PDF (966KB) ( 29 )  
    The aim of this study was to evaluate the accuracy and reproducibility of a morphological contour  interpolation (MCI) based segmentation method for the volumetric measurement of bone grafts around implants.  Three 3D-printed models (one with a cylinder and two with a geometrically-complex form) were fabricated to  simulate implant placement with a simultaneous guided bone regeneration (GBR) procedure. All models were  scanned using a cone beam computed tomography (CBCT) instrument with the same parameters. The true  volumes of the bone grafts in the models were assessed using computer-aided calculation (controls). For the test  measurements, both manual and MCI-based methods were used. A comparison between the measured and true  volumes was performed to evaluate the accuracy. The coefficients of variation of repeated measurements were  calculated to evaluate the reproducibility. In addition, the execution time was recorded and a comparison between  the two methods was performed. The high accuracy of the MCI-based method was found with differences between  the measured value and actual volume, which never exceeded 7.3%. Excellent reproducibility was shown, with  coefficients of variation never exceeding 1.1%. A shorter execution time was observed for the MCI-based method  than for the manual method. Within the confines of this study, the MCI-based method may be suitable for  volumetric measurements of grafted bone around implants.
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    Real-Time Deformation Simulation of Kidney Surgery Based on Virtual Reality
    JING Mengjie (荆梦杰), CUI Zhixin(崔志鑫), FU Hang (傅航), CHEN Xiaojun (陈晓军)
    2021, 26 (3):  290-297.  doi: 10.1007/s12204-021-2295-3
    Abstract ( 270 )   PDF (3888KB) ( 47 )  
    Virtual reality-based surgery simulation is becoming popular with the development of minimally invasive  abdominal surgery, where deformable soft tissue is modelled and simulated. The mass-spring model (MSM)  and finite element method (FEM) are common methods used in the simulation of soft tissue deformation. However,  MSM has an issue concerning accuracy, while FEM has a problem with efficiency. To achieve higher accuracy and  efficiency at the same time, we applied a co-rotational FEM in the simulation of a kidney with a tumour inside,  achieving a real-time and accurate deformation simulation. In addition, we set a multi-model representation for  mechanical simulation and visual rendering. The implicit Euler method and conjugate gradient method were  adopted for setting and solving the linear system. For a realistic simulation of surgery, constraints outside the  kidney and between the kidney and tumour were set with two series of mechanical properties for the two models.  Experiments were conducted to validate the accuracy and real-time performance.
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     Automatic Segmentation Method for Cone-Beam Computed Tomography Image of the Bone Graft Region within Maxillary Sinus Based on the Atrous Spatial Pyramid Convolution Network
    XU Jiangchang (许江长), HE Shamin (何莎敏), YU Dedong (于德栋), WU Yiqun (吴轶群), CHEN Xiaojun, (陈晓军)
    2021, 26 (3):  298-305.  doi: 10.1007/s12204-021-2296-2
    Abstract ( 194 )   PDF (967KB) ( 40 )  
    Sinus floor elevation with a lateral window approach requires bone graft (BG) to ensure sufficient  bone mass, and it is necessary to measure and analyse the BG region for follow-up of postoperative patients.  However, the BG region from cone-beam computed tomography (CBCT) images is connected to the margin of  the maxillary sinus, and its boundary is blurred. Common segmentation methods are usually performed manually  by experienced doctors, and are complicated by challenges such as low efficiency and low precision. In this study,  an auto-segmentation approach was applied to the BG region within the maxillary sinus based on an atrous  spatial pyramid convolution (ASPC) network. The ASPC module was adopted using residual connections to  compose multiple atrous convolutions, which could extract more features on multiple scales. Subsequently, a  segmentation network of the BG region with multiple ASPC modules was established, which effectively improved  the segmentation performance. Although the training data were insufficient, our networks still achieved good  auto-segmentation results, with a dice coefficient (Dice) of 87.13%, an Intersection over Union (Iou) of 78.01%,  and a sensitivity of 95.02%. Compared with other methods, our method achieved a better segmentation effect,  and effectively reduced the misjudgement of segmentation. Our method can thus be used to implement automatic  segmentation of the BG region and improve doctors’ work efficiency, which is of great importance for developing  preliminary studies on the measurement of postoperative BG within the maxillary sinus.   
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    Image Registration Technique for Assessing the Accuracy of  Intraoperative Osteotomy for Pelvic Tumors by 3D-Printed Patient-Specific Templates
    QU Yang (曲扬), YAN Mengning (严孟宁), LI Xiaomin (李小敏), WU Bing (吴兵), LIU Siyu (柳思宇), WANG Liao (王燎), WU Wen(武文), AI Songtao(艾松涛)
    2021, 26 (3):  306-311.  doi: 10.1007/s12204-021-2297-1
    Abstract ( 155 )   PDF (2664KB) ( 25 )  
    The study aimed to explore the feasibility of an image registration technique for assessing the accuracy  of intraoperative osteotomy of pelvic tumors by 3-dimensional (3D)-printed patient-specific templates. Patients  with malignant pelvic tumors who were admitted to our hospital between March 2014 and December 2020 were  retrospectively enrolled. Patients underwent hemi-pelvic resection and reconstruction by 3D-printed individualized  prostheses. The registration between the designed model and the postoperative segmented model of the prosthesis  was used to obtain the intraoperative osteotomy plane and reduce metal artifacts in postoperative computed  tomography (CT) images. The distance and angle between the planned and actual osteotomy planes were then  used to assess the accuracy of the intraoperative osteotomy. Eight patients with 13 osteotomy planes were  enrolled, including four males and four females. The median age at the time of imaging examination was 44 years  (range, 33—54 years). All intraoperative osteotomy planes were assessed successfully. The mean distance between  the planned and true intraoperative osteotomy planes was ?0.69 cm (?7.5—7.35 cm), and the mean angle was  6.57?±3.36?(1.05?—11.88?). This new assessment method of registering the designed model and the postoperative  CT segmented model of the prosthesis may be used to assess the accuracy of intraoperative osteotomy for pelvic  tumors, using 3D printed patient-specific templates.
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    Application of 3D Digital Reconstruction and Printing to the Diagnosis and Treatment of Iliac Vein Compression
    YANG Chenghao (杨成昊), LU Xinwu (陆信武), JIANG Wenbo (姜闻博), YE Kaichuang (叶开创), ZHAO Zhen (赵振), WANG Xuhui (王旭辉), WANG Penghui (王鹏辉), FEI Yebao (费业宝), WANG Wei (王伟), YIN Minyi (殷敏毅)
    2021, 26 (3):  312-318.  doi: 10.1007/s12204-021-2298-0
    Abstract ( 187 )   PDF (507KB) ( 37 )  
    The objective of this research was to explore the feasibility and clinical application of a new diagnostic  imaging method for the diagnosis and treatment of iliac vein compression (IVC) based on three-dimensional (3D)  digital reconstruction and printing. This study included patients with chronic venous disease (CVD) who were  admitted to the Department of Vascular Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University  School of Medicine, from January to March, 2019, and underwent computed tomography venography (CTV) to  detect IVC. CTV findings were used to reconstruct 3D-printed models of blood vessels. A total of 17 patients (5  men and 12 women) with IVC, who were primarily diagnosed with CTV, were included in this study. In addition,  24 significant venous compression sites were found in 17 patients, of which 7 patients had only one compression  site (41.2%), nine patients had two compression sites (52.9%), and one patient had three compression sites (5.9%).  3D digital reconstruction and printing is a convenient, noninvasive, and accurate diagnostic imaging method that  provides a clear and accurate evaluation of veins and arteries, as well as the anatomical positional relationship for  the diagnosis and treatment of IVC.
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    Application of 3D Printing and WebGL-Based 3D Visualisation Technology in Imaging Teaching of Ankle Joints
    LI Xiaomin (李小敏), DAI Xiaoqing(戴晓庆), GUO Jiuhong (郭久红), QU Yang (曲扬), WU Bing (吴兵), LIU Siyu (柳思宇), WAN Daqian (万大千), AI Songtao(艾松涛)
    2021, 26 (3):  319-324.  doi: 10.1007/s12204-021-2299-z
    Abstract ( 222 )   PDF (344KB) ( 43 )  
     With the rapid development of medical technology, 3D printing technology with realistic representation  can perfectly display static human anatomy, while 3D visualisation technology based on Web Graphics Library  (WebGL) can promote the rigid replication characteristics of traditional teaching models and express the dynamic  spatial relationship between different anatomical structures. Medical students traditionally have less cognition of  ankle ligament sprains. In this study, computed tomography (CT) and magnetic resonance imaging (MRI) data of  the ankle joints of volunteers were used to print models of the ankle bone, tendon, and ligament using 3D printing  technology, and a real-time interactive 3D digital model of the functional ankle joint was designed using 3D  visualisation based on WebGL and 2D image real-time rendering technology for interactive teaching. The utility  of the 3D printing model combined with the WebGL-based 3D digital teaching model was evaluated in comparison  with traditional teaching methods in 24 medical students. The results showed that the total score of students  in the experimental group (mean ± SD, 79.48 ± 12.93) was significantly better than that of the control group  (61.00±14.94) with P <0.05. The practical test scores of the experimental group (18.00±2.70) were significantly  higher than those of the control group (13.67 ± 4.96) with P < 0.05. In the satisfaction survey, the feedback  questionnaire showed that the interactive teaching model of 3D printing technology combined with WebGL-based  3D visualisation technology was recognised by students in terms of quality and overall satisfaction. In addition,  female students who used 3D printing combined with WebGL-based 3D visualisation technology as learning aids  had a greater difference in practical test scores from the control group than male students. This study has  demonstrated that the interactive teaching mode of 3D printing combined with WebGL-based 3D visualisation  technology is beneficial to the teaching of medical imaging, enriching the learning experience of students, and  increasing the interaction between teachers and students.
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    Technique Note for Staged Resection of Giant Invasive High-Cervical Schwannoma and Reconstruction of  C2—C4 with 3D Printing Technique
    SUN Xiaojiang(孙晓江), ZHAO Changqing (赵长清), YANG Erzhu(杨二柱), LI Hua (李华), ZHANG Kai (张凯), CHENG Xiaofei(程晓非), JIANG Wenbo (姜闻博), CHENG Zhihua(程志华), GUO Zhilin (郭智霖), DAI Kerong (戴尅戎), ZHAO Jie (赵杰)
    2021, 26 (3):  325-333.  doi: 10.1007/s12204-021-2300-x
    Abstract ( 163 )   PDF (2223KB) ( 45 )  
    A schwannoma is a relatively common benign spinal cord tumour; however, giant schwannomas with  extensive cervical vertebral erosion are rare, and the treatment strategy, especially the reconstruction of the upper  cervical vertebra, remains a challenge for spine surgeons. Here, we present a rare case of giant invasive highcervical  schwannoma with extensive erosion of the C2—C4 vertebral bodies and tumour-encased left vertebral  artery. The surgical strategy and the reconstruction of C2—C4 with 3D printing techniques were discussed and  performed. A 32-year-old man presented to our department with complaints of gait disturbance and weakness in  both upper and lower extremities. His limb muscle strength was grade 2 or 3/5, and he exhibited severe bladder  and bowel dysfunction on admission. X-ray and computed tomography of the cervical spine showed an extremely  large erosive lesion at the C2—C4 vertebral bodies and lateral masses. Magnetic resonance imaging of the cervical  spine showed a large soft-tissue mass on the left aspect of the C2—C5 vertebra and in the spinal canal at the  C3—C4 level. A staged schwannoma resection, instrumented fixation, and reconstruction of C2—C4 with 3D  metal printing technique were performed. The patient achieved good postoperative outcomes and returned to  normal daily life with no recurrence of schwannoma during follow-up for four and a half years. The 3D-printed  implant achieved solid fusion with the remaining cervical spine. We performed staged resection of the giant  invasive high-cervical schwannoma and reconstructed the erosive C2—C4 vertebra with the assistance of a 3D  printing technique. 3D printing technology has facilitated the design and manufacture of customised implants for  complex surgical procedures.
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    3D-Printed Porous Titanium Augments for Reconstruction of Massive Bone Defect in Complex Revision Total Knee Arthroplasty: Implant Design and Surgical Technique
    KAN Tianyou(阚天佑), XIE Kai(谢凯), QU Yang(曲扬), AI Songtao (艾松涛), JIANG Wenbo (姜闻博), WU Haishan (吴海山), WANG Liao(王燎), YAN Mengning(严孟宁)
    2021, 26 (3):  334-338.  doi: 10.1007/s12204-021-2301-9
    Abstract ( 159 )   PDF (1065KB) ( 23 )  
    Reconstruction of severe bone defects in revision total knee arthroplasty (TKA) remains a challenge  for orthopaedists. The progression of medical imaging and additive manufacturing technology has enabled the  rapid manufacture of custom-made implants, and 3D-printed augments with interconnected pore structures have  become an alternative approach for the reconstruction of bone defects in revision TKA, especially in patients  with complex bone defects. The size and location of the bone defect were determined by thin-layer computed  tomography (CT; layer thickness is 1mm) after reduction of artifacts. The 3D reconstruction models of the host  bone were obtained based on thin-layer CT imaging. The custom-made augmentation was designed according to  the 3D reconstruction bone model. The augmentation had an interconnected porous structure on the bone-implant  interface to achieve biological fixation. After the design was complete, the 3D model of augment was exported in  STL format, and augments were fabricated with Ti6Al4V powder using electron beam melting. Thin-layer CT  and 3D reconstruction bone models are accurate methods for evaluating periprosthetic bone loss after artifact  reduction. The 3D-printed augments perfectly match the bone defects during surgery. 3D-printed augmentation  is an effective approach for the reconstruction of bone defects in revision TKA. Thus, surgeons and engineers  should carefully evaluate the bone defect during augment design to avoid a mismatch between the augment and  host bone. 
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    Using a Patient-Specific 3D-Printed Surgical Guide for High Tibial Osteotomy: A Technical Note
    JIANG Xu, (江旭), XIE Kai (谢凯), LI Bo (李波), HU Xumin (胡旭民), WU Haishan (吴海山), GAO Liangbin (高梁斌), WANG Liao (王燎), YAN Mengning (严孟宁)
    2021, 26 (3):  339-345.  doi: 10.1007/s12204-021-2302-8
    Abstract ( 220 )   PDF (1004KB) ( 72 )  
    Patient-specific instrumentation (PSI) enables a more accurate alignment of the lower limbs in a high  tibial osteotomy (HTO) than in traditional surgery; however, the current design of commercial PSIs is not perfect.  Therefore, we designed a new patient-specific surgical guide to improve the accuracy of the osteotomy and verified  its reliability through a clinical operation. Here, we describe a patient with isolated medial-compartment bilateral  knee osteoarthritis, accompanied by a varus deformity of the proximal tibia. The patient was treated with HTO  using a patient-specific 3D-printed surgical guide. We concluded that the patient-specific 3D-printed surgical  guide improved the accuracy of the osteotomy and the alignment of the lower limb. 
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    3D-Printed Guide Plate Assisted Osteochondral Transplantation for the Treatment of Large Talar Defect:#br# Case Report and Literature Analysis
    YAO Xiangyun (姚湘云), GAN Yaokai (干耀恺), SHI Dingwei(史定伟), XU Chen (徐辰), ZHAO Jie(赵杰), DAI Kerong(戴尅戎)
    2021, 26 (3):  346-351.  doi: 10.1007/s12204-021-2303-7
    Abstract ( 150 )   PDF (1360KB) ( 43 )  
    Osteochondral lesion of the talus (OLT) is a common cause of ankle pain that often occurs in the  talar dome and leads to talar cartilage and subchondral bone damage. Osteochondral autograft transplantation  is a logical treatment option. It is known that if the cartilage does not heal properly after injury, it degenerates,  and osteoarthritis worsens. A three dimensional (3D)-printed guide plate can be used to find the curved articular  surface from the donor site which optimally fits the defect in the talus. Herein, we present the case of a 28-year-old  man who had an open injury from the crash of a tricycle in the right ankle at the age of 5. Radiographs revealed  a large defect in the medial talar dome that affected nearly half of the talar dome. We performed the debridement  of the ankle lesion. An osteochondral autograft was harvested from the medial femoral condyle (MFC) with the  help of a personalised 3D-printed guide plate. This 3D-printed guide plate simulated the contour of a specific  area in the talar dome, which involved the site of the defect. The autograft was then transplanted into the talus  defect. The efficacy of this technique was evaluated at 2, 4, and 7 months after surgery and proven to be reliable.
     
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    Progress in the Application of 3D Printing Technology in Spine Surgery
    SUN Xiaojiang (孙晓江), YANG Erzhu (杨二柱), ZHAO Changqing (赵长清), CHENG Xiaofei (程晓非), ZHANG Kai (张凯), TIAN Haijun (田海军), DING Baozhi (丁宝志), LI Hua (李华), JIANG Wenbo (姜闻博), DAI Kerong(戴尅戎), ZHAO Jie(赵杰)
    2021, 26 (3):  352-360.  doi: 10.1007/s12204-021-2304-6
    Abstract ( 166 )   PDF (1228KB) ( 50 )  
     We are in the midst of exciting advancements in new technologies and innovative research in precision  medicine. Among these, 3D printing is one of the most frequently seen in clinical orthopaedic settings. This  new technique has been adopted in a vast range of applications in spine surgery, such as producing anatomical  models, surgical templates, preoperative plans, and spinal implants. Some studies on 3D printing technologies  in spine surgery have reported the benefits of this emerging technology with more effective manufacturing, more  visualisation for communication, and more precise navigation for screw insertion and osteotomy. In addition, in  customised implant design and fabrication processes, 3D printing products with anatomical adaptions and complex  porous microstructure show some attractive advantages in terms of fit and osteoinductivity. However, there are  still some concerns about the safety and feasibility of the application of 3D printing technology in spine surgery.  We review the literature on and share our experiences with the application of 3D printing from the beginning  of collaborations between doctors and computer-aided design (CAD) designers to the final follow-up of clinical  patients. 
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    Design and Application of 3D Printing Based Personalised Pelvic Prostheses
    WU Junxiang (吴钧翔), LUO Dinghao(罗丁豪), XIE Kai (谢凯), WANG Lei (王磊), HAO Yongqiang (郝永强)
    2021, 26 (3):  361-367.  doi: 10.1007/s12204-021-2305-5
    Abstract ( 180 )   PDF (930KB) ( 32 )  
    In this paper, we describe the design and surgical process of personalised pelvic prostheses fixation  through 3D printing according to different Enneking pelvic tumour zones: the ilium (Zone I), acetabulum (Zone  II), and pubis and ischium (Zone III). A 3D model of the pelvis was reconstructed using imaging data, and the  parameters on the planes of the acetabulum and pelvic incisal margin were measured. The main body of the pelvic  prosthesis was constructed, a porous structure was designed on the bone-prosthesis interface, and the movement  paths, lengths, and diameters of screws were planned. By combining the pathological model and osteotomy guide,  limb salvage reconstruction was performed in patients with pelvic tumours. Preoperative and postoperative data  were compared to verify the prosthesis stability. Our investigation revealed that the long-term survival of pelvic  reconstruction prostheses depends on accurate matching with the bone defect area, good initial stability, and a  porous structure to allow bone ingrowth. 
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    Application of Virtual Reconstruction 3D-Printed External Fixation Helmet in Early Functional Treatment of Facial Fracture
    GE Weiwen (葛卫文), WANG Yun (王昀), GE Kui(葛奎), WU Jiajun (吴嘉骏), FAN Jingxian (范晶娴), YANG Tianye(杨天页), WANG Qi (王齐), XU Bing (徐兵)
    2021, 26 (3):  368-371.  doi: 10.1007/s12204-021-2306-4
    Abstract ( 183 )   PDF (577KB) ( 27 )  
    Facial fracture repair is time-dependent. Early reduction and fixation after trauma help with later  repair. Abnormal healing caused by delayed repair increases not only the difficulty of reconstruction, but also the  risk of aesthetic or functional defects. Digital technology was used to model local trauma in three dimensions.  The fracture fragments were reset, and the facial shape was reconstructed on the reset model. After resampling,  3D printing was used to construct a personalised external fixation helmet. Combined with the posterior nasal  passage lift reduction technique, early reduction of the mid-face fractures was performed. Through the early  application of a 3D-printed personalised external fixation helmet to a patient with a comprehensive fracture, the  helmet manufacturing process and application methods were introduced, and the effect of this application was  investigated. In the treatment of facial fractures, the early application of a 3D-printed personalised external  fixation helmet is conducive to fracture reduction and fixation and reduces the difficulty of later reconstruction. 
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    Primary Clinical Research of a Patient Specific Implant System for an Old Zygomaticomaxillary Complex Comminuted Fracture
    ZHANG Tianjia (张天嘉), JIANG Tengfei (姜腾飞), LI Biao (李彪), WANG Xudong(王旭东)
    2021, 26 (3):  372-376.  doi: 10.1007/s12204-021-2307-3
    Abstract ( 179 )   PDF (570KB) ( 36 )  
    The objective of this study was to expound a novel surgical management technique assisted by patientspecific  implants (PSIs) for comminuted fractures of the zygomaticomaxillary complex (ZMC). The aim of this  study was to explore the feasibility of using PSIs to accurately restore and fix comminuted fractures. A male patient  with an old ZMC comminuted fracture was used to describe the workflow, technique, and method. Computerassisted  surgical simulation was used to determine the optimal plan for the reduction of bone segments prior to  surgery. The PSIs were used to accurately guide the surgeon’s position of the bone segments, as planned, during  the operation. Oral panoramic films and cephalometric films were taken immediately at 1, 3, 6, and 12 months  after the operation, while computed tomography images of the whole skull were taken immediately, half a year,  and one year after the operation. The patient’s follow-up showed that the zygomatic symmetry recovered well  post-surgery and the patient was satisfied with the outcome. This new surgical method greatly improved the facial  symmetry of this patient. 
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    Effects of Mandibular Extractions with Clear Aligners: A Finite Element Analysis
    FENG Qiping (冯齐平), CHU Fengting (储沨婷), CHEN Rongjing (陈荣敬), PAN Xiaogang (潘晓岗)
    2021, 26 (3):  377-382.  doi: 10.1007/s12204-021-2308-2
    Abstract ( 287 )   PDF (844KB) ( 36 )  
    This study was aimed at analysing the mechanical characteristics of different mandibular extraction  modes using a clear aligner. Three experimental schemes of different extraction patterns were designed to treat  mandibular crowding, including extraction of one mandibular central incisor, bilateral first premolars, and bilateral  second premolars. The stress distribution during the space closing was analysed using the finite element method.  When a central incisor was extracted, a significant retraction force was found in the anterior region, in line  with the design expectation. The posterior teeth, which were designed to move mesially, acted as anchorage for  anterior retraction, and were subjected to a mesial force. The anterior teeth were retracted when the bilateral  first premolars were extracted. The lateral incisors and canines were subjected to a significant distal force and  moment, while the central incisors and canines were subjected to lingual forces and moments. Additionally, the  canines were subjected to a non-designated intruding force. The molars were designed to move mesially when the  bilateral second premolars were extracted. All molars were subjected to a significant mesial force, while the lingual  force on the front teeth was slight. The bilateral second molars were subjected to non-design mesial moment and  extrusive force. The bilateral first molars were subjected to a non-designated mesial moment, and the bilateral  first premolars on both sides were subjected to non-designated intrusive force and distal moment. When one  incisor was extracted, attachments on the anterior teeth had a controlling effect on the tooth axis, but the anterior  teeth still tended to tilt. When the bilateral first premolars were extracted, the anterior teeth showed a tendency  for lingual inclination. The risk of distal inclination of the canines and lingual inclination of the central incisor  increased. When the bilateral second premolars were extracted and the posterior teeth were designed to move  mesially, the teeth on both sides of the extraction sites showed an obvious bowing effect. 
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    Effect of Attachment on Movement Control of the Central Incisor Using Invisible Orthodontics: In-Silico Finite Element Analysis
    PAN Shengxuan (潘晟轩), ZOU Diyang (邹第洋), PAN Xiaogang(潘晓岗), TSAI Tsung-Yuan (蔡宗远)
    2021, 26 (3):  383-390.  doi: 10.1007/s12204-021-2309-1
    Abstract ( 190 )   PDF (1560KB) ( 29 )  
    We aimed to study the influence of attachment on central incisor movement control using invisible  orthodontics with different translation or rotation targets. In this study, cone-beam computerised tomography  was used to scan one 15-year-old volunteer’s teeth. Three-dimensional models of the mandibular central incisor,  removable orthodontic appliance, and a rectangular attachment were reconstructed. A non-linear finite element  simulation was used to analyse the influence of attachment on the stress distribution of the periodontal ligament of  the central incisor under tooth rotation, mesial translation, and labial-lingual translation. For mandibular central  incisor correction, using rectangular attachments increased the translation by up to 9.6%, increased the maximum  stress on the periodontal ligament during the mesial translation correction, and reduced unwanted labial-lingual tilt  by up to 40% during the rotation of the tooth. However, wearing an attachment during labial-lingual translation  had no significant effect on the orthodontic results of the mandibular central incisor. In the mandibular central  incisor’s invisible orthodontic, the rectangular attachment appliance increased the displacement and alleviated the  side effect after applying mesial translation and tooth rotation. For labial-lingual translation, the application of a  rectangular attachment had no pronounced effect on the results. 
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    Total Talar Replacement Using a Novel 3D-Printed Prosthesis for Recurrent Giant Cell Tumour of the Talus
    GAN Yaokai (干耀恺), DAI Kerong (戴尅戎), LI Jianying (李健瑛), SHI Dingwei (史定伟), SHEN Lu (沈陆), JIANG Wenbo (姜闻博)
    2021, 26 (3):  391-397.  doi: 10.1007/s12204-021-2310-8
    Abstract ( 246 )   PDF (1816KB) ( 24 )  
    In our case, 3D printing was used to fabricate a custom-made titanium alloy total talar prosthesis as  a mirror image of the contralateral healthy talus for a 16-year-old girl who underwent right talar resection for a  recurrent giant cell tumour (GCT) of the talus. A porous surface was used over the neck and tail of the talus  prosthesis to promote soft tissue attachment and improve the stability of the prosthesis. Pre-drilled medial and  lateral holes were prepared for ligament repair and attachment. Eighteen months after the operation, there was  no tumour recurrence, and the patient walked without symptoms. The Musculoskeletal Tumour Society score was  22/30, the American Orthopaedic Foot and Ankle Society score was 88/100, and the prosthesis was well positioned  on radiographs. The short- and medium-term outcomes indicated that 3D-printed modular talar prostheses could  be an effective treatment option. 
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    Clinical Observation of 3D Printing Technology in Insoles for Flexible Flatfoot Patients
    WANG Yitian (王一天), JIANG Wenbo (姜闻博), GAN Yaokai, (干耀恺), YU Yang (于洋), DAI Kerong, (戴尅戎)
    2021, 26 (3):  398-403.  doi: 10.1007/s12204-021-2311-7
    Abstract ( 196 )   PDF (567KB) ( 48 )  
    Flatfoot is defined as the flattening of the medial arch of the foot, and it is classified into flexible  flatfoot and rigid flatfoot based on whether the flattening of the medial arch of the foot can be reset when  standing on toes. The insole is the most basic and common treatment, which is relatively cheaper and easier to  adopt. Three-dimensional (3D) printing, an emerging technology characterized by high machining accuracy and  use of various materials, can be utilised in personalised insoles, which have good application prospects. Further  research on the clinical effects of 3D-printed insoles is still needed. In this study, 64 cases of 3D-printed insoles  were clinically observed. The results showed that 3D-printed insoles had statistically positive effects in treating  flatfoot (P = 0.000 17), and with adjustment and adaptation, their comfort and clinical effect can be improved.  This study provides an empirical reference for further large-scale clinical control research. 
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    Workflow and Principles for Precisely Designing a Custom-Made  Polyetheretherketone Implant Applied in Irregular Craniofacial Bone Defects
    JIANG Taoran (姜陶然), YU Zheyuan (俞哲元), YUAN Jie (袁捷), XU Liang (徐梁), DUAN Huichuang (段惠川), ZHOU Sizheng (周思政), CAO Dejun(曹德君), WEI Min (韦敏)
    2021, 26 (3):  404-410.  doi: 10.1007/s12204-021-2312-6
    Abstract ( 178 )   PDF (1023KB) ( 57 )  
    Irregular craniofacial bone defects caused by craniofacial fractures always result in craniofacial bone  and contour asymmetry and should therefore be reconstructed. Polyetheretherketone (PEEK) is an ideal substitute  for autologous bone grafts and has been widely used in craniofacial bone defect reconstruction. The precise design  of custom-made PEEK implants is particularly important to optimise reconstruction. Herein, the workflow and  principles for the design and manufacture of PEEK implants are summarised, and a protocol for the precise design  of an irregular craniofacial bone defect PEEK implant is presented. According to the method and principles, the  design flow was efficient and could be standardised, and design errors could be avoided as much as possible.
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    Formability of Printing Ink for Melt Electrowriting
    HAN Yu (韩煜), SUN Binbin (孙彬彬), JIANG Wenbo(姜闻博), DAI Kerong (戴尅戎)
    2021, 26 (3):  411-415.  doi: 10.1007/s12204-021-2313-5
    Abstract ( 180 )   PDF (678KB) ( 28 )  
    3D printing, also called additive manufacturing, is being used increasingly in tissue engineering. However,  the printing accuracy remains limited, making it difficult to prepare a tissue engineering scaffold with high  precision and high porosity. Melt electrowriting (MEW) technology is based on extrusion printing, in which an  extruded material is pulled by the action of an electric field, thereby reducing the fiber diameter and improving  the printing accuracy. However, MEW technology imposes high requirements on the material properties, and  therefore, few printing materials are currently available for use in this process. The present study investigates  the characteristics and molding conditions of polycaprolactone, a commonly used printing material, as well as  other materials such as poly(lactic-co-glycolic acid), poly(ethylene glycol) diacrylate/polyethylene oxide, gelatin  methacrylate, and hyaluronic acid methacrylate for MEW applications, and develops new and suitable inks for  MEW that will provide more and better choices for constructing a bioactive scaffold in future tissue engineering  research. Experiments suggest that a printing ink should have low electrical conductivity, suitable viscosity, and  high curing speed for realizing successful printing.
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    Review on Corrosion Characteristics of Porous Titanium Alloys Fabricated by Additive Manufacturing
    GAI Xin, (盖欣), BAI Yun (白芸), LI Shujun (李述军), WANG Liao (王燎), AI Songtao (艾松涛), HAO Yulin (郝玉琳), YANG Rui (杨锐), DAI Kerong (戴尅戎)
    2021, 26 (3):  416-430.  doi: 10.1007/s12204-021-2314-4
    Abstract ( 184 )   PDF (1891KB) ( 59 )  
    Porous titanium and its alloys have been considered as promising implants owing to their low elastic  modulus and capability to provide channels for bone growth. Currently, additive manufacturing (3D printing)  techniques have been successfully applied to produce porous titanium alloys owing to the advantages of controllable  and precise fabrication. Considering the safety aspect, an understanding of corrosion in porous titanium alloys  and the corresponding mechanisms is important for their long-term application in the human body. In this  paper, the recent progress in improving the corrosion properties of porous titanium alloys fabricated via 3D  printing techniques is reviewed. The effects of pore type, porosity, electrolyte, and modification of the material  on the corrosion properties of porous titanium alloys are introduced and discussed. In addition, the limitations of  traditional methods for measuring the corrosion performance of porous titanium alloys were analysed. Perspectives  for evaluating and improving the corrosion performance of porous titanium alloys using new methods are provided. 
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