|Year : 2015 | Volume
| Issue : 2 | Page : 51-53
3D printing: The cutting edge of digital medicine
Bone and Joint Research Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200240, China
|Date of Web Publication||25-Jan-2016|
Bone and Joint Research Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200240
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dai K. 3D printing: The cutting edge of digital medicine. Digit Med 2015;1:51-3
Three-dimensional (3D) printing is emerging as a promising technology as a result of the rapid development of a series of high technologies, such as computer technology (especially computer graphics technology), biomaterials, automatic control technology, laser, digital manufacturing, Internet, etc. It has been or is being widely applied to multiple disciplines and industries, demonstrating its great potential. Medical application of 3D printing has already become one of the focuses in digital medicine, a newly emerging discipline.
3D printing, also known as additive manufacturing (AM), refers to a variety of processes applied to build a three-dimensional object layer by layer. In general, the process of 3D printing starts with 3D computer modeling. Then, successive layers of raw materials are formed to create 3D physical objects according to computer-assisted design under automatic control of various 3D printers with different theories.
Medical application of 3D printing technology can be classified into four main categories: medical modeling and non-implanted medical devices, medical implants, and 3D printing assisted tissue engineering and bio-printing.
The first category, 3D printing of medical models and non-implanted medical devices, includes the printing of models of human tissues, structures and organs, braces, splints, glasses, hearing aid devices, prosthetics, etc. This category of 3D printed products will not be implanted within human body. The requirement of biocompatibility regarding materials in this category is relatively low, as long as no local allergy or adverse effects are detected.
Regarding the medical models, a 3D physical model of human body close to real structures can be printed out based on the 3D computer model reconstructed from medical images, thus facilitating the teaching and research of anatomy and pathology, surgical planning, implant designing, surgical rehearsal, simulation of implant installation, etc.
With the development of medical imaging, 3D printing could build personalized models of almost any structures related to medical education and clinical practice. A real size 3D model containing the target lesion and its surrounding structures could be precisely printed out, helping the doctors better appreciate the morphology of the lesion and its anatomic relationship with the surrounding structures, especially its relationship with important blood vessels and nerves. An accurate medical model is of critical importance in making a detailed and practical surgical plan, improving the success rate and reducing surgical risk. 3D printed medical models are widely applied in hepatobiliary surgery, cardiovascular surgery, orthopaedic surgery, cranio-maxillofacial surgery, and so on. A classic example regarding medical application of 3D printing was the separation surgery of thoracopagus conjoined twins. The conjoined heart models can be reconstructed based on the imaging data, and then be printed out to help with surgical simulation, improving the odds of a successful separation surgery. Meanwhile, 3D model is a powerful tool to facilitate doctor-patient communication. It is true that 3D reconstructed virtual models on the computer screen might also display information similar to that provided by the 3D printed models, but it is no match for holding a physical model in your own hands.
3D printing is also widely applied in the research and development of non-implanted medical devices. For example, 3D printed prosthesis and brace have already shown their potentials to better fit patients' personal anatomical morphology by tailoring themselves to customized sizes and shapes. 3D printed surgical guide can assist in performing surgeries with higher accuracy, thus reducing or even avoiding unnecessary mistakes caused by surgeons' imperfect spatial perception. Accurate and safe placement of screw within the pedicle is a crucial step in spinal surgery. 3D printed patient-specific drill guide with pre-determined trajectory has been considered as a promising solution. The drill guide could find its position by fitting perfectly with adjacent bony structure, and then, the drill ducts help surgeons find the perfect trajectory for screw insertion with easy, which can avoid injury to important neurovascular structures. This is also true with the dental implant surgery.
The second category refers to 3D printing of medical implants, which are manufactured to replace a missing biological structure, and support a damaged anatomic structure. Thus, both the biocompatibility and mechanical properties should be considered. Thus, metal alloys are the mainstream biomaterials for this category. Artificial joint is a good example for the application of 3D printing in the manufacture of medical implants. Most of the commercialized artificial joints are off-the-shelf; thus it is hard to avoid mismatch. Personalized joint implants show their potential to reduce mismatch between the implants and adjacent anatomical structures. Metal 3D printing shows its potential to revolutionize the manufacture of personalized artificial joints. Traditionally personalized implants are manufactured by computer numerical controlled machining, which is called the subtractive manufacturing. The advent of metal 3D printing revolutionizes the production mode by transforming subtractive manufacturing to additive manufacturing. Shanghai Ninth People's Hospital is well known for its contribution to the development of hemipelvic replacement. After the pelvic tumors have been resected, extensive irregular bony defects are quite common, which are impossible to be reconstructed with conventional tumor implants. As a senior customer of 3D printing, Shanghai Ninth People's Hospital utilized 3D printing to improve the reconstruction for those with huge bony defects, by making physical models, surgical guides and customized orthopaedic implants. Shanghai Ninth People's Hospital purchased its own metal 3D printer with electron beam melting system (Arcam TM , Sweden). Initially, metal 3D printed customized implants were used in the reconstruction after the resection of pelvic tumors. Then, they were extended to revision surgeries after different joint replacements, severe osteolysis, spine surgery and so on. Among those with cranio-maxillofacial injuries, trauma, and birth defects, a perfect reconstruction has a huge impact on their life. Thus, 3D printed personalized implants are quite attractive to cranio-maxillofacial surgeons and patients.
The third category refers to 3D printing assisted tissue engineering, which might become a reality in the near future. Traditionally, a variety of methods have been reported for preparing porous structures to be employed as scaffolds. Because most of the techniques are limited regarding the control of porosity and pore size, computer-assisted design and 3D printing have been introduced to tissue engineering. The scaffold is then realized by using ink-jet printing of polymer powders or through Fused Deposition Modeling of a polymer melt. 3D printed scaffold has a stronger capability of controlling the porosity and pore size, which is critical for tissue engineering. A variety of biomaterials could be applied in the manufacture of biologic substitutes with 3D printing, including various ceramics and polymers. No matter which materials have been used, both biological and biomechanical performance of the applied biomaterials should be considered. These biomaterials could be further categorized into non-degradable and degradable materials. Non-degradable materials are traditionally favored by medical community for its biocompatibility. However, degradable materials are even more attractive, since they can be degraded and replaced by regeneration of adjacent tissues after a period of time.
The fourth category is bio-printing. As the cutting edge of 3D printing, most of bioprinters are probably in the experimental phase. However, in the future, bioprinters might revolutionize medical practice as yet another element of medical industry. Research is being conducted on vessel, artificial heart, kidney, tendon, cartilage, muscle, trachea, cornea, skin, liver or liver structures, as well as other organs. However, the final products of bio-printing are still far away from being functionally and clinically applicable.
As a branch of digital medicine, medical 3D printing, taking CT or MRI images as a template, builds accurate real size and structure of medical models, medical devices and implants. These types of clinical procedures are becoming more and more common among doctors and medical researchers all over the world. Many surgeons have applied 3D printing in clinical practice to improve the accuracy of surgical procedures. Sometimes, 3D printing could change the previously inoperable surgery to a successful surgery. It is hoped that bio-printing will eventually be able to produce functional organs that can be transplanted into patients.
From the perspective of digital technology, to promote the medical application of 3D printing technology, attention should be paid to the software design and its application, including R&D of intelligent medical image processing software, individualized product design software, and the system software for cloud-based manufacturing and management of individual product, and to actively promote the research on 3D printing requirement-based human tissue imaging system, joint application with navigation system, and the personalized adaptation research of medical implantation materials. Besides, we should immediately set out to make the standards and specifications on medical application of 3D printing, including those on corresponding special test and evaluation technique and standardized operating system. In addition, it is essential to establish normalized training and management system for doctors and engineering technicians and also hospital qualification requirements, and to strengthen the update of 3D printing technology and the exchange of personalized concept.
| Authors|| |
Prof. Kerong Dai is a senior member of Chinese Academy of Engineering (CAE), a foreign corresponding member of French National Academy of Medicine, and an expert in orthopedic surgery and biomechanics. He graduated from Shanghai Medical University (i.e. Fudan University Shanghai Medical College) in 1955, and was a visiting fellow in Mayo Clinic in the United States from 1983-1984. He was the Tenured Professor and the former president of Shanghai Ninth People's Hospital Affiliated to Shanghai Second Medical University, and also the director of the Department of Orthopedics. He is currently the director of Shanghai Clinical Medical Center of Joint Surgery, of the Bone and Joint Research Center of Shanghai Jiao Tong University (SJTU) School of Medicine, of the Engineering Research Center of Digital Medicine, Ministry of Education, and of the Stem Cell and Regenerative Medicine Transformation Base of the Institute of Translational Medicine of SJTU. He pioneered to apply shape-memory alloy within human body internationally. He has made breakthrough in quantitative evaluation of gait and body balance, stress-shielding effect of internal fixation, osteoporotic fracture, basic study of artificial joint and customized artificial joints, stem cell transplantation and gene therapy for bone regeneration, and the application of 3D printing technology in musculoskeletal system. He has won more than 45 prizes, among which are the National Invention Prize of China (the second prize), the National Science and Technology Progress Award (the second and third prizes), and a number of municipal and ministerial awards. In addition, he has gained more than 40 patents. He has published over 500 papers, and compiled 59 monographs.