Abstract
Interventional studies differ from observational studies in that one or more specific interventions are evaluated. Randomized controlled trials remain the gold standard for interventional studies and can take different forms. In surgical studies, the three types of randomized controlled trials most commonly encountered are: (I) trials that compare two different medical treatments for patients undergoing surgery; (II) trials that evaluate two different surgical techniques and (III) studies that compare surgery vs. non-operative management. When an intervention is to be evaluated but a randomized controlled trial is not feasible, alternative interventional study designs may be considered.