3 D Printing, a new tool in orthopaedic surgery
Journal Title: Journal of Bone and Joint Diseases - Year 2018, Vol 0, Issue 0
Abstract
3 D printing has revolutionized the world of engineering and is now knocking on health care applications. Engineering prototypes were developed by casting and forging as a step in designing a new product. These would undergo the process of physical testing, before the designs were accepted or modified. Time and cost in such process were a major challenge to overcome. Next came the era of virtual designing and testing which was a big change in the manufacturing world. The near final designs of manufacturing still had to be made by cumbersome time-consuming methods. The arrival of 3 D printing created this special opportunity of virtual planning and rapid prototyping. Anything and everything in the manufacturing industry is going through the process of 3 D printing of prototypes. Over the years material possibilities in 3 D printing have expanded and near final designs can be printed in the material required also. 3 D printers have become fast and also cheap for designing prototypes. Let us be introduced to this new tool and its applications in orthopaedic surgery. What is 3D printing? 3D printing is a process of creating a three dimensional object from a virtual or digital 3D image. It is done by addition of successive layers one over the other to create a complex 3D model from the data received from the virtual image. Whole object is made up of many successive layers laid down in process of 3D printing. Therefore, this process is also known as additive manufacturing. What are the techniques of 3D printing? There are various techniques of 3D printing. Few common ones used are:- 1) Stereolithography: – It is one of the oldest methods of 3D printing. It is based on principle of photopolymerisation. Photopolymerisation is solidification of photosensitive resin with the help of UV light. It is useful in creating complex models but requires post finishing and support structures [1]. Other similar techniques are digital light processing and continuous liquid interface production based on same principle. 2) Fused Deposition Modeling: – It is one of the most popular techniques used now days. This process works by material being melted and sprayed through a nozzle to 3D print a cross section of an object each layer at a time. This process repeats until the object is completed. Although it is easy to operate, poor finishing and requirement of support structure are its disadvantages [1]. 3) Selective Laser Sintering: -In this process, 3D printing is done by melting of powder to form a successive layer and then creating an object through successive layer deposition. No support structure is required and its speed is high but finishing is poor and precision to object details is low due to particular powder particles size. 4) Electron Beam Melting:-In this case, electron beam is used instead of laser beam to melt the metal powder in high vacuum to create object layer by layer it creates high density object retaining properties of the metal. Printing speed is good but caution is required while handling with X-Ray What are the materials used in 3D printing? Materials used in 3D printing are as follows: – Plastics: – 1) Poly lactic acid (PLA):-It is derived from natural sources like sugarcane, corn starch, etc. and hence bio-degradable and eco-friendly. 2) Acrylonitrile butadiene styrene (ABS):- It is also known as “LEGO PLASTIC”. It consists of pasta like filaments which gives its firmness and flexibility. It is available in various colors which can be used for manufacturing of stickers and toys. 3) Polyvinyl Alcohol Plastic (PVA):- It s not suitable for high strength objects but can be used as a support material of dissolvable variety. It is a low cost option. 4) Polycarbonate (PC):-It s only used in printers with nozzles operating at higher temperature. It can be used in manufacturing of low cost plastic fasteners and molding trays. Powders: – 1) Polyamide (Nylon): – It s having high strength and flexibility and that is why it is used to print everything from fasteners and handles to toy cars and figures. 2) Alumide: – It is mixture of polyamide and gray aluminum with its grainy and sandy appearance used for strong 3D models Resins: – 1) High detail resins: – This is used for manufacturing of small models with complex details for example facial models are printed with this type of resin. 2) Paintable resin: -This is used for printing smooth 3D surfaces with cosmetic appeal. 3) Transparent resin: – It is strongest type of resin with transparent and smooth surfaced property used in manufacturing of various 3D printed objects. Metals: – 1) Stainless steel: -It is used for printing of various utensils, cookware, implants, etc. which ultimately comes in contact with water. 2) Bronze: – Used to make vases and other fixtures. 3) Gold: – Used for printing rings, earrings, bracelets and necklaces. 4) Nickel: – Used for the printing of coins. 5) Aluminum: – Used for printing thin metal objects. 6) Titanium: – The preferred choice for strong, solid fixtures and orthopaedic implants. Cost Of 3D Printing Over the last 30 years many inventions have been done in 3D printing technology. Different machines were developed over the years to make the process better and smoother. The expense of 3D printing mainly depends on the cost of machine and material. Metal 3D printing machines costs more compare to other machines. Machines cost according to 3D printing technique: Fused Deposition Modeling, Stereolithography, Selective Laser Sintering which can range from 25,000 INR to more than 1,00,000 INR depending on size and manufacturer of the 3D printer. Material cost depends on the type of filament used and the volume of material used for example printing a model of 3D pelvis in PLA will cost around 2,000 INR and printing a pre-contoured plate in PLA will cost around 50-75 INR. And there is hidden cost of machine maintenance, R & D and labor if you do it on large scale. 3D printing cost has decreased in last few years and expected to decrease more as technology is improving day by day due to increasing competition in market. So, machines will be better in terms of speed, smoothness and ease of use. 3D printing (rapid prototyping) in medicine- 3D printing is useful in medical field in various ways, few examples are mentioned below: – 1. A 3D printed “polypill” has been developed for patients of diabetes and hypertension on multiple medications [2]. “Polypill” is designed to contain several drugs which all releases on different times and in different amount as required[3, 4]. It is helpful to improve compliance in patients suffering from a range of ailments, such as the elderly, are often dependent on taking multiple pills throughout the day 2. Help in pre operative virtual planning and patient specific 3D printing provide addition predictability in complex surgical cases for example Custom made implants are used in cranioplasty surgeries done for cranial defects, mandible reconstruction done in complex mandible fracture, maxillofacial surgeries [5] etc. 3. 3D printed designed grafts are useful for management of cardiovascular diseases in valve replacement surgeries and vascular grafts used in congenital heart diseases. 4. 3D printing in dentistry has been used for years by dental labs to create crowns, veneers, bridges and implants in various dental surgeries [6]. Major limitation of this technology lies in time and cost spent in making 3D models. 3D printing is already well integrated in medical practice and their application varies from anatomical models (for surgical planning) to surgical guides and implant. Application of 3D printing in orthopaedics: – 1) Surgical planning: – 3D printing is useful pre-operative planning of various complex surgeries like a) Corrective osteotomies and deformity correction: – 3D printing is very useful in planning osteotomy level and angle, 3D printed wedges, Pre contoured plates for post osteotomy fixation in cases like Valgus osteotomy hip, Valgus or varus osteotomy around knee, High tibial osteotomy (HTO), Corrective osteotomies around elbow, planning on 3D printed models for complex deformities, etc. b) Trauma: – 3D printing can be useful in Acetabulum fractures by designing pre contoured plates, virtual surgical planning for reduction maneuver and designing guiding jigs for column screws placement. In all complex peri-articular fractures virtual planning for fixation strategy and contouring of plates can be done preoperatively. In Spine trauma guiding jigs for pedicle screws placement along with determination of screw sizes can be done. In maxillofacial trauma pre contoured plates can be very useful. c) Tumors: – Planning resection with guiding jig, patient specific prosthesis especially when modular prosthesis is not available (Metal 3D printing) and planning reconstruction of defects with bone graft (auto graft/ allograft/osteochondral grafts) can be very useful in tumor resection surgeries. d) Arthroplasty: – In hip, Knee or shoulder arthroplasty surgeries (especially in revision surgeries with altered anatomy) planning for bone defects reconstruction, guiding jigs for correct prosthesis placement, mimicking on 3D printed model to ascertain whether implant of particular size can be placed or not can be a beneficial exercise done with the help of 3D printing. 2) Research: – For morphometric studies on human skeleton need of dry bones analytic study can be avoided as accuracy of 3D printed models has already been proved. Also, larger sample size can be taken. Analysis of suitability of Pre-contoured plates on different ethnicities can be studied with the help of 3D printing. 3) 3D printing can be used inAcademics and display purpose in orthopaedics. 4) Doctor patient interactioncan be improved with the help 3D models regarding making patient understand about the disease and management. Over the years supportive branches of medicine have had a major role in development of the orthopaedic specialty. Musculoskeletal imaging has had one of the most importantcontribution in this field. X rays brought the first revolution in understanding orthopaedic diseases and today it is unimaginable to manage patients without it. Advanced imaging like CT, MRI, and Bone Scan etc gave a further insight. 3 D reconstructed images of a CT scan provide a very good real time understanding, especially in understanding fractures and complex deformities. 3 D printing in future may be one step more in a similar direction. It would open up a new dimension in education, patient communication, planning and executing customized solutions in Orthopaedics. It would be of immense use if all of us understand this new tool and start thinking of its applications to improve patient outcome in all spheres of orthopaedic science
Authors and Affiliations
Lalit Maini
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