What is a Clinical Trial?
World Health Organization defines clinical trial as: “any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes. Interventions include but are not restricted to drugs, cells and other biological products, surgical procedures, radiological procedures, devices, behavioral treatments, process-of-care changes, preventive care, etc.” 
Importance of Clinical Trials
A recent 3DHEALS blog discussed the significant update on 3D printed anatomical models and surgical guide. As with any other new medical procedures and devices, the economic future of 3D printed medical devices and services will depend on the future reimbursement landscape, which requires solid clinical evidence to back the claims on not just safety and efficacy, but also “value-added”. That is, the new technologies are not just equivalent but adding significant new benefits to patients and society. Accumulation of clinical evidence largely depends on clinical trials, which are well-designed research studies meeting a set of requirements. Typically, the success of a clinical trial is manifested as a publication in a high-impact peer-reviewed clinical journal. Therefore, clinical trials are not only important to patients, healthcare providers, but also companies interested in promoting new technologies, devices, and procedures in healthcare.
Clinical Trial Registries
According to the U.S. Department of Health and Human Services, there are currently 24 public clinical trial registries all over the world.  Registering a clinical trial before enrolling the first patient is important because being timely listed as a clinical trial in a public registry is a condition of publication by the International Committee of Medical Journal Editors (ICMJE) since 2004.  ICMJE is an important organization because it is the working group of editors from some of the most reputable medical journals. The working group meets annually to update guidelines on publishing scholarly work in medical journals. 
The current members of the ICMJE include Annals of Internal Medicine, British Medical Journal, Bulletin of the World Health Organization, Deutsches Ärzteblatt (German Medical Journal), Ethiopian Journal of Health Sciences, Iranian Journal of Medical Sciences, JAMA (Journal of the American Medical Association), Journal of Korean Medical Science, New England Journal of Medicine, New Zealand Medical Journal, The Lancet, Revista Médica de Chile (Medical Journal of Chile), Ugeskrift for Laeger (Danish Medical Journal), the U.S. National Library of Medicine, and the World Association of Medical Editors.
Additionally, regulatory authorities around the world began to require the posting of clinical trial information and, in some cases, the submission of summary results to a publicly accessible registry. Even some research funding agencies are now encouraging or requiring the registration and results reporting of the clinical trials they fund. 
Of the many registries, two are the most important:
Both registries are recognized by ICMJE, accessible to the public at no charge, open to all prospective registrants, managed by non-profit organizations. Both have a mechanism to ensure the validity of the registration data and are searchable online. 
Clinicaltrial.gov registry is maintained by the U.S. National Library of Medicine and includes 300K+ research studies in all 50 states in the United States as well as in 209 countries globally. 
The ICTRP Search Portal is maintained by the World Health Organization. It provides a single point of access to information about ongoing and completed clinical trials all over the world. This makes searching for non-U.S. based clinical trials a lot easier. The Data Providers of the ICTRP Search Portal currently include:
- Australian New Zealand Clinical Trials Registry (ANZCTR)
- Brazilian Clinical Trials Registry (ReBec)
- Chinese Clinical Trial Register (ChiCTR)
- Clinical Research Information Service (CRiS), Republic of Korea
- Clinical Trials Registry – India (CTRI)
- Cuban Public Registry of Clinical Trials (RPCEC)
- EU Clinical Trials Register (EU-CTR)
- German Clinical Trials Register (DRKS)
- Iranian Registry of Clinical Trials (IRCT)
- Japan Primary Registries Network (JPRN)
- Pan African Clinical Trial Registry (PACTR)
- Peruvian Clinical Trials Registry (REPEC)
- Sri Lanka Clinical Trials Registry (SLCTR)
- Thai Clinical Trials Register (TCTR)
- The Netherlands National Trial Register (NTR)
Ongoing and Completed Clinical Trials
There are many good reasons to use these registries beyond just registering your own clinical trials:
- Learning about good clinical trial design. This is especially applicable to completed trials with publications, which you can find at the end of this article
- Learning about global trends. Based on a recent publication, China and the U.S. are the number one and two leading countries with the greatest number of completed and ongoing clinical trials. 
- Learning about industrial trends. In the same review article , the field of orthopedics, dentistry, and Craniomaxillofacial surgery are the most active in doing research. To industries, these could be a good starting point for finding market-product fit and product development.
- Getting inspired. The creative use of a new tool (and associated new concepts), like 3D printing, never cease to inspire many. Here is a shortlist of recently successfully completed clinical trials as a demonstration of creative use of a powerful tool that could be very impactful in our future healthcare:
Regardless of the technology in focus, conducting successful clinical trials will be a critical step to find the truth, assessing new markets, and establish any new practice paradigms.
- From ideas to long-term studies: 3D printing clinical trials review