Hierarchy of Evidence
Meta-Analysis (Level I Evidence; Grade A Recommendation)
Randomized Trial (Level I Evidence; Grade A Recommendation)
Randomized Trial (Expertise-Based Design)
Observational Study (Cohort, Case Series)
Prospective Observational Study (Level II Evidence; Grade B Recommendation)
Case-Control Study (Level III Evidence; Grade B Recommendation)
Retrospective Case Series (Level IV Evidence; Grade C Recommendation)
Case Study: The Study to Prospectively Evaluate Reamed Intramedullary Nails in Tibial Fractures Trial (Level I Study)
Understanding Statistics in Trauma Outcome Studies
What is the p Value?
The 95% Confidence Interval
Measures of Central Tendency and Spread
Measures of Treatment Effect (Dichotomous Variables)
Common Statistical Tests
Common Errors in the Design of Orthopedic Studies
Type II Errors (β-Error)
Type I Error (α-Error)
The Misuse of Subgroup Analyses in Orthopedic Outcome Studies
Statistical Versus Clinical Significance
Study Power and Sample Size Calculation
Comparing Two Continuous Variables
When the Outcome Measure is Dichotomous (Proportion)
Measuring Patient Health and Function
What is Health-Related Quality of Life?
Common Outcome Instruments Used in Trauma
Utilizing Outcome Studies in Decision-Making (Evidence-Based Orthopedics)
What is Evidence-Based Orthopedics?
Finding Current Evidence in Trauma
User’s Guide to Evaluate an Orthopedic Intervention
Incorporating Evidence-Based Orthopedics into Daily Trauma Practice
The Future of Outcome Studies in Orthopedic Trauma
Appendix: Sample Size Calculations
1. Continuous Variables
2. Dichotomous Variables
Adapted from JBJS Guidelines. Available online at http://www2.ejbs.org/misc/instrux.dtl#levels.
Adapted from Griffin D, Audige L. Common statistical methods in orthopaedic clinical studies. Clin Orthop Relat Res. 2003;413:70–79.
NA, not available; Y, one or two articles found in support of this attribute; YY, multiple articles supporting this attribute.
From Beaton DE, Schemitsch E. Measures of health-related quality of life and physical function. Clin Orthop Relat Res. 2003;413:90–105.