Avoiding Systematic Bias in Orthopedics Research Through Informed Variable Selection: A Discussion of Confounders, Mediators, and Colliders

There are 3 common variable types in orthopedic research—confounders, colliders, and mediators. All 3 types of variables are associated with both the exposure (eg, surgery type, implant type, body mass index) and outcome (eg, complications, revision surgery) but differ in their temporal ordering. To reduce systematic bias, the decision to include or exclude a variable in an analysis should be based on the variable's relationship with the exposure and outcome for each research question. In this article, we define 3 types of variables with case examples from orthopedic research. Please visit the following https://youtu.be/V-grpgB1ShQ for videos that explain the highlights of the article in practical terms.