In recent years, 3D printing techniques have been revolutionising the healthcare industry everywhere in the world. 3D printing has the ability to print personalised medical devices (e.g. individualised orthopaedic implants) and patient-specific surgical simulations in a significantly short amount of time. This revolution is driven by the need for speed and cost efficiency, and it improves the quality of life through customisation possibilities, a shorter recovery period and a lower risk of side effects  . That is, however, if 3D-printed parts meet the quality requirements as imposed by the healthcare industry.
3D printing, also known as additive manufacturing (AM), is a relatively new technique and was founded in the 1980s. The ISO and ASTM standards define additive manufacturing to be the “process of joining materials to make parts from 3D model data, usually layer upon layer, as opposed to ‘subtractive manufacturing methods’, such as machining.”   There are different AM techniques, such as powder bed fusion, material extrusion and binder jetting. Powder bed fusion is a commonly used technique which starts with a powder bed. Thermal energy will then selectively fuse regions of the powder bed into parts. Selective laser melting (SLM) and electron beam melting (EBM) are two examples of a powder bed fusion technique.
In recent years, AM techniques have been applied in a large number of studies on tissue engineering, which led to the successful fabrication of bone and cardiac tissue. Advancements in AM techniques and the starting materials led to the use of 3D printing in the field of orthopaedic implants. These orthopaedic implants are mostly used for structure reinforcement, and are inserted inside the corpus. Implants can either be temporary, such as plates and screws, or permanent, such as a hip, a knee or fingers.
ADVANTAGES FOR THE HEALTHCARE INDUSTRY
3D-printed patient implants can be customised and will provide a better fit for the patient, in addition to reducing the recovery period. One of the main advantages of additive manufacturing is that it is not subject to any design constraints, as opposed to conventional manufacturing techniques. Additive manufacturing allows for complex geometries without a significant increase in building time. On top of that, there is no need for tooling or moulds, which means it is possible to build several patient specific implants in one go.
However, to prevent the rejection of orthopaedic implants, it is important to have a correct design, biocompatible materials and blueprint of the bone properties. The 3D-printing environment generally makes use of biocompatible materials such as titanium-6aluminium-4vanadium (Ti6Al4V), cobalt-chromium (CoCr) or 316L stainless steel. And in addition to biocompatible materials, a precise design of pores and porosities is necessary in order to mimic the bone properties. Orthopaedic implants with adequate pore structures and appropriate mechanic properties allow for tissue in-growth and thus anchor the implant to the surrounding bone, preventing loosening of the implant.
STANDARDS AND REGULATIONS
Since 3D-printed parts with healthcare purposes are categorised as medical devices, they are subject to increasing standards and regulations to guarantee their quality. It is expected that an orthopaedic implant heals and does not cause any harm. Quality is assured by controlling the starting materials, processes and systems. Although control of the processes and systems is comparable to the pharmaceutical industry, control of metal powder as a starting material is more specific for additive manufacturing. The requirements on quality control of metal powder are described in ISO 9001, ISO 13485 and ASTM standards. Besides the overall quality control, post-market surveillance serves as an important practice to reduce risks and approve quality. Complaints, CAPAs and changes can influence the design and production of 3D-printed parts with the purpose of improving quality for the patient.
Additive manufacturing or 3D printing can contribute to the health of millions of people, provided that the quality requirements of the printed parts are met. Meeting these quality requirements is a challenge, since 3D printing must meet multiple ISO requirements and legislations (hybrid quality system). Therefore, investing in quality management is essential. Quality management helps make sure your product is safer for the patient and it benefits the manufacturing process as well.
 Bourell, D. (2017). Materials for additive manufacturing. Manufacturing Technology, 66, p. 659 – 681.
 Sing, SL. (2015). Laser and electron-beam powder-bed additive manufacturing of metallic implants: a review on processes, materials and designs. Wiley Periodicals online library.