Scientists are usually not clinicians and most clinicians are not scientists. Very few scientists that I know are involved in clinical trials and only a small percentage of active clinicians, particularly those taking care of people with spinal cord injury, are active in the research laboratory.

Physicians are licensed to practice medicine and surgery. Just having an MD is not sufficient. Even having a medical license is not usually sufficient. One has to be a practicing physician in an accredited hospital. In order to carry out a clinical trial in the United States and receive grant funding to do so, one also usually needs to be affiliated with an academic institution.

Some physician scientists can do both science and clinical trials. For example, John McDonald is able to do both. He is a rare commodity, a man who has a leadership role in both arenas.