system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Evidence based ortho research is based on the following studies:
assistant
The correct answer is  Evidence-based medicine pyramid. 
The levels of evidence are appropriately represented by a pyramid as each level, from bottom to top, reflects the quality of research designs (increasing) and quantity (decreasing) of each study design in the body of published literature. For example, systematic reviews are higher quality and more labor intensive to conduct, so there is a lower quantity published.