Using 3D Printing for Pre-planning of Orthopedic Surgeries, a Review

Background: Recent developments in 3D printing have gave orthopedic surgeons among a novel technology that has the ability to revolutionize preoperative planning. The appearance of 3D printing technology (3DPT) enables the digital preoperative plan & simulation to move from the virtual phase to the reality phase. Numerous fields of medicine are lately benefiting from the operate of 3D printing, including the arising part of 3D printing in orthopedic surgery. Methods: We searched on PubMed and Google Scholar databases in January 2020 to find papers and studies about using 3D printing in orthopedy for aim of preplanning. The key words for search were (“3D printing” OR “3D-printed Model” OR “three-dimensional Printer”) AND (“Orthopedy” OR “Orthopedics” OR “Orthopedics”) AND (“Surgery” OR “Operation”) AND (“Pre-planning” OR “Plan”) AND (“Fracture” OR “Trauma”) that we used compound. We exclude the papers which their titles or abstracts were not relevant. At last, we select the most related papers to use in this article. Results: The search on PubMed found 80 Papers and on Google Scholar found 104 papers. After excluding similar and unrelated papers, 44 papers were selected for this review article. Conclusion: Almost all studies have shown us that using a 3D model can have a very positive effect on the surgical process and its outcomes, as well as patient and surgeon satisfaction. Therefore, we anticipate that this technology will be used in many orthopedic surgeries in the near future. They recommend that the 3D method provides a better short-term healing effect and the lives of many patients models in planning of ip arthroplasty with cetabular defects. in several patients, CT scans cannot provide a perfect understanding of the pelvic destruction. this study perfect understanding of acetabular


INTRODUCTION
Three-dimensional (3D) printing appearing in numerous subjects of medicine is appear as a clinically suggesting technology aimed at rapid prototyping of reachable creations. Recent developments in 3D printing have gave orthopedic surgeons among a novel technology that has the ability to revolutionize preoperative planning, surgical tool development, and custom orthopedic implant formation [1]. Orthopedics move into the digital era with the rapid improves of digital technology [2]. The appearance of 3D printing technology (3DPT) enables the digital preoperative plan & simulation to move from the virtual phase to the reality phase. 3D digital images promote to shape a 3D significant target. This will gives a valuable actual indication for surgeons to achieve the diagnosis and the separate operation plan, which considerably corrects the safety & effectiveness of surgery [3]. This technology creates use of data from resource such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT Scan), Computer Aided Designs (CAD), Cone Beam Computed Tomography (CBCT) or from any Reverse Engineering Techniques (RET) [4]. Usual presurgical planning is based on the running of two-dimensional data obtained by incomes of traditional radiography & photography. This method limits the extensive understanding of different bony structure movements and this needs surgeon's very well visualization abilities [5,6]. Several present surgical processes are difficult and need help to obtain a satisfactory esthetic outcome, or to prevent damaging important structure of the body [6].
An amount of examines report better outcomes for patients with orthopedic deformities by using patient-specific 3D printed models for surgical planning [7]. Several clinical centers have yet to adopt the technology as part of usual clinical treatment, despite the presence of 3D printing in medicine for many years, not merely due to high prices and problems with segmentation-which are commonly understood as the bottleneck of the procedure [8]. The medical images integration, usually benefit for patient diagnoses, with the newest 3D printing technology predict to be very useful for therapeutic and diagnostic reasons. Numerous fields of medicine are lately benefiting from the operate of 3D printing, including the arising part of 3D printing in orthopedic surgery [9].

METHODS
We searched on PubMed and Google Scholar databases in January 2020 to find papers and studies about using 3D printing in orthopedy for aim of preplanning. There were 4 different researchers involved in the selection process, and they were independently judging the included studies. The key words for search were ("3D printing" OR "3D-printed Model" OR "threedimensional Printer") AND ("Orthopedy" OR "Orthopedics" OR "Orthopedics") AND ("Surgery" OR "Operation") AND ("Pre-planning" OR "Plan") AND ("Fracture" OR "Trauma") that we used compound.
We exclude the papers which their titles or abstracts were not relevant, language problems, hadn't novelty or be similar to other studies, and not be suitable for our article. At last, we select the most related papers to use in this article. However, there was no limits on the time, but we did our best to choose most new and novel studies.

RESULTS
The search on PubMed found 80 Papers and on Google Scholar found 104 papers. After excluding similar and unrelated papers, 44 papers were selected for this review article.

About 3D Printing
Additive manufacturing technique, also known, as 3D printing method, is a procedure that from 3D digital or other electronic data resource, creation 3D printed things. It was firstly used for printing objects in industry, and next presented into medicine [10]. 3D printers by using computer software to build substantial items from data, shape custom-formed targets. Technological improvements in the last decade, less the price of 3D printers, such that their usage has expanded into fields not traditionally mixed with rapid prototyping [1]. The three-dimensional printing technology primary medical used in 1990 was explained by Mankovich et al. In orthopedic surgery, two mainly kinds of techniques used for 3D printing, namely additive techniques & subtractive. The subtractive method is milling for medical application, in which from a block of polyurethane or other foam the physical model will be milled. The advantage of this method is low material price. However, the geometric accuracy is weak and cannot be sterilized for intraoperative use. Other techniques normally used in orthopedic surgery are Additive techniques, in which the models create during layer by layer with liquid-like or powder-like plastic or metal material. Compared with subtractive method, additive techniques can create difficult cavities & structures. In orthopedics, generally additive technologies are selective laser sintering (SLS), stereolithography and fused deposition modelling (FDM). SLS uses high-power laser to combine little powders made of metal, plastic, glass or ceramic into a physical model based on the 3D images made by computer-aided plan. It is able to deliver a more accurate geometry. However, the cost of SLS is high and cannot be employed in operation. Stereolithography uses an optical light energy source to scan above a vat of light-curable resin, solidifying specific parts on the liquid surface. The ground of the liquid case gradually decreases, which rises the material's depth as the model increases and successive layers of resin are cured on top of each other. FDM mechanism is extraction and solidification of materials in layers. Layers achieve by a heated polymer deposition with operate of a computercontrolled extrusion nozzle. In this technique, can choose various colors and materials. The geometric accuracy is elevated and can be used in operation. But, the quality of surface is not good enough and the production time is long [11]. Costs are different for these models of printers, in ranging of less than $1000 to more than $100,000. 3D printers are becoming more available and less expensive [1].

Process of 3D Printing
Image acquisition is the primary and most important stage. The quality of models depends on the quality of data establishes and the later processing; so, for making a high-quality 3D model, the quality of source images is very important. Presently, image data that use for 3D printing are obtained from MRI, CT or other imaging modalities. In the CT scan, bony tissues have a relatively higher contrast and exposure than that of soft tissue, then in orthopedic surgery CT images are commonly the sources of image for 3D printing [11]. CT image files change to stereolithography (STL) 3D printable format by segmentation and smoothing procedure. Digital Imaging and Communication in Medicine (DICOM) image tons process by MIMICS (Materialise, Leuven, Belgium) and then export as 3D-printable STL files for each patient ' s CT scan. For noise speckles, the STL files checking by MeshLab (Visual Computing Lab, ISTI-CNR), which will remove noises. Using the automatic mesh repair function by NetFabb (NetFabb GmbH, Lupburg, Germany), STL files adjust for 3D printing. Then the modified STL file transfer to the 3D printer [7]. 3D printing materials that use in orthopedics are poly lactic acid (PLA), stainless steel, sintered powdered metal, titanium, ceramic, nitinol, bone-like (e.g., CTbone [xilloc, geleen, the netherlands]), plastics (e.g., polyjet [stratasys, eden prairie, minnesota], polyether ketone ketone, polyether ether ketone) [5,12].

Uses of 3D Printing in Specific
Anatomical Areas of Orthopedic Surgery . Acetabular 3D models could decrease operative time and bettered understanding of difficult acetabular anatomy and fracture shape to strategy the best locating of a reduction clamp and the trajectory of screws. They moreover noted simulated as a reference through the real operation. A resident did this surgical simulation and aided as a useful training technique. They recognized the ideal position of anatomical plates using 3D printed clavicle models for fractures of the clavicle [9]. The orthopaedic surgeons believed that the 3D models were less satisfied with its usage in preoperative planning but was helpful for contact with patients [16]. ii.

Fig.
Again, in 2019 Chunhui Chen et al. used 3D printing models to restructure the distal radius fractures in patients; Their results were exactly similar to 2017study [17].

Hip joint
Hip Arthroplasty is a common and important orthopaedic surgery. There are some interesting studies that use 3D printing for preplanning of this operation, which you can see in Table 1.

Pelvis
i. Hurson   Before being adjusted, acetabular cup, buttress, augment and cage sizes were examine using the 3Dmodels, and improving the preoperative decision-making procedure. For decreasing the damage of neurovascular injury, screw trajectory simulation was Complex pelvic deformities were improved estimated and cured with better precision by 3D printing technique. Actual-size models helped to precise operation simulation, so making better preoperative planning and anatomical appreciation. The precision and price-effectiveness of the method should verify invaluable as a device to aid clinical exercise [18].
Using 3D printing technology in total hip arthroplasty (THA) in 74 up was about 24 Harris scores and time of postoperative weight bearing of the cases in the 3D printing group were better than conventional group. The postoperative infection and loosening degrees were upper in the 3D printing group. They recommend that the 3D printing method provides a better short-term healing effect and improve the lives of many patients models in planning of ip arthroplasty with cetabular defects. in several patients, CT scans cannot provide a perfect understanding of the pelvic destruction.
3D models created by CT data can assist surgeon in planning of complex acetabular reconstruction. 3D plaster models in this study detected high accuracy in the perfect understanding of acetabular bone deficiency [20].
printed models are very useful in orthopedy. Surgeons use these models for pre , humerus [ s were improved estimated and cured with better precision by size models helped to precise operation simulation, so making better preoperative planning and anatomical appreciation. The precision and method should verify invaluable as a device to aid clinical exercise ime of postoperative weight bearing of the cases in the 3D printing group were better than conventional group. The postoperative infection and loosening degrees were upper in the 3D printing group. They recommend that the 3D printing method term healing effect and improve the lives of many patients [19]. 3D models created by CT data can assist surgeon in planning of complex acetabular 3D plaster models in this study detected high perfect understanding of printed models are very useful in orthopedy. Surgeons use these models for presurgeries the donor position dimensions and moreover for fixing the donor position defect by planning best match iliac bone and superficial circumflex iliac artery flaps. All reconstructed thumbs were fine, but partial flap necrosis occurred in one patient, which was managed on bandages. Reconstructed thumbs had total great appearance and functionality [31].

Spine
i.
Ralph J. Mobbs et al. in 2017 evaluated the utility of 3D models for complex spinal pathologies. The authors presented two patients in which 3D printing technology was used for surgical planning as a preoperative template, and for a specificdesigned titanium prosthesis: one patient with a C1/C2 chordoma who experienced tumor resection and vertebral reconstruction, and second patient with a specific-designed titanium anterior fusion cage for an uncommon congenital spinal deformity. In both reported cases, the specific-designed and specific-built implants were simply positioned, which eased the surgery and reduced the operation time, avoiding additional complex reconstruction. Radiological follow-up for both patients established successful fusion at nine and twelve months, respectively [32]. ii.
Po-Chen Chen et al. in 2019 used 3D printing technique to assist spinal deformity surgery. The engineers created drill patterns based on the bony surface anatomy and the trajectory of pedicle screws. During a preoperative mock surgery on 3D spine model, their safety and efficiency were estimated. Intraoperative monitoring no significant difference in neurologic deficit or Somatosensory evoke potential (SSEP) and motor evoke potential (MEP) was noticed. According to postoperative CT scans, the satisfactory rate was 97.1 percent [33]. iii.
Wongthawat Liawrungrueang et al. in 2020 used a 3D model for a patient of thoracolumbar junction pure bilateral facet joint dislocation without facet fracture, that is a very rare injury. They did an early examination using a 3D printied model so as to help with orthopaedic surgical planning, emergency initial open reduction and instrumentation with fusion. Neurological status was healthier. The 3D model should be a normal examination in rare cases of orthopaedic surgical planning [34].

CONCLUSION
In this article, we reviewed studies conducted around the world on orthopedic surgery preplanning using a 3D printed model, and tried to further present new and innovative articles.
Almost all studies have shown us that using a 3D model can have a very positive effect on the surgical process and its outcomes, as well as patient and surgeon satisfaction. The advantages of this technology, which have been repeatedly mentioned in previous studies are reduced surgical time and number of fluoroscopies during surgery, and reduced patient bleeding and postoperative complications. Probably all this is due to the fact that there is a model before surgery that completely similar to the patient's anatomy, which makes the surgeon more ready and with better planning for the surgery, or even before the surgery can practice on the model. Therefore, we anticipate that this technology will be used in many orthopedic surgeries in the near future.

LIMITATION
There were some limitations in writing this review article. One of them was language problem, especially articles in Chinese that we couldn't use them. Another was the studies which hadn't got obvious results.

SUGGESTION
Due to the benefits of using a printed 3D model as a tool for preoperative planning, as evidenced by previous studies and research, there are still many orthopedic surgeries that do not use this useful tool. Therefore, we suggest using 3D models for more orthopedic surgeries (For example in Tibial deformity, Knee Arthroplasty, Genuvarum or Genuvalgum, and etc) and reporting their results.

CONSENT
It's not applicable.

ETHICAL APPROVAL
It's not applicable.