We’ve all heard a lot about 3D printing (or additive manufacturing) over the past few years. The basic principle consists of laying down material layer by layer, with the shape of the product being determined by a computer model. One of the most exciting applications of 3D printing is in medicine. The 3D printing method can be altered to print the materials used in implants, such as fracture plates, or even to print biological tissue!
Personalised surgery involves producing surgical implants that fit the patient exactly. Images, e.g. CT scans, taken of the patient can be used to design a computer model of the implant/tissue to be printed. Where previous implants had to be manoeuvered and bent to fit in the patient, these personalised ones will slot in perfectly, reducing tissue damage and preventing the creation of defects in the implant which may have otherwise caused it to break.
Models of patients’ anatomies can also be made. These are then used by surgeons to practice complicated surgeries and solve any problems prior to performing the actual surgery on the patient. Cost of surgery is thus reduced, as well as time spent under anaesthesia, blood loss, and often recovery time. This method is already saving lives: 3D printed models of conjoined twins allow surgeons to decide which organs to assign to which child, and to plan the highly complex 26 hour surgery far in advance1. Rajesh Krishnamurthy, M.D., lead author and chief of radiology research and cardiac imaging at Texas Children’s Hospital, stated in a press release2: “This case was unique in the extent of fusion. It was one of the most complex separations ever for conjoined twins.” The twins were successfully separated, but without the printed model the outcome of surgery would likely have been very different.
So far I’ve only mentioned printing artificial materials. Arguably more exciting, the race is on to be the first to print living tissue and implant it into humans. Scientists in Ireland have developed a novel method for printing bone using the body’s natural development.3 A cartilage model is 3D printed that imitates the natural precursor to bone during early stages of development in humans. The cartilage precursor could then mature into the desired bone.
One major setback in the development of 3D printed organs has been the inability to keep the tissue alive once printed. In the body, blood vessels carry blood, and with it oxygen and nutrients, to each and every cell. Researchers have struggled to produce blood vessels within the 3D constructs. However, a breakthrough may have been discovered by Bertassoni et al.4 – they successfully implemented a strategy involving the construction of artificial tubes as templates. The tubes were lined with endothelial cells (the cell type that makes up the walls of blood vessels) before removing the templates.
Personalised implants can currently be made within 2-3 days5,6 although in a busy hospital environment it is usually longer. The ultimate aim would be to have specialised 3D printers (configured to print live tissue) in every hospital. So, made to order artificial implants are currently available and only going to get cheaper, and made to order body parts may be just around the corner.
1 B Millsaps, For Hope and Faith: the power of 3D printing helps separate conjoined twins, <https://3dprint.com/108732/separating-conjoined-twins/>, 2015 (accessed 24/01/2017).
2RSNA Press Release, CT and 3-D printing aid surgical separation of conjoined twins, < https://press.rsna.org/timssnet/media/pressreleases/PDF/pressreleasePDF.cfm?ID=1843>, 2015 (accessed 24/01/2017).
3A C Daly, G M Cunniffe, B N Sathy, O Jeon, E Alsberg, D J Kelly, 3D Bioprinting of Developmentally Inspired Templates for Whole Bone Organ Engineering, Adv Healthc Mater., 2016, 5(18), 2353-62.
4L E Bertassoni, M Cecconi, V Manoharan, M Nikkhah, J Hjortnaes, A L Cristino, G Barabaschi, D Demarchi, M R Dokmeci, Y Yang, A Khademhosseini, Hydrogel bioprinted microchannel networks for vascularization of tissue engineering constructs, Lab on a chip, 2014, 14(13) 2202-11.
5M Cronskar, L E Rannar, M Backstrom, K G Nilsson, B Samuelsson, Patient-Specific Clavicle Reconstruction Using Digital Design and Additive Manufacturing, Journal of Mechanical Design, 2015 137(11), 4.
6M Cronskar, L E Rannar, M Backstrom, Implementation of Digital Design and Solid Free-Form Fabrication for Customization of Implants in Trauma Orthopaedics, Journal of Medical and Biological Engineering, 2012 32(2), 91-96.