The classic randomized clinical trial is difficult to apply to the
evaluation of surgical procedures. After reviewing the structure and
rationale of cohort studies and randomized clinical trials, four types of
bias in randomized clinical trials that present difficulties in clinical
studies are identified. Other problems that may limit the willingness of
orthopaedic surgeons to conduct randomized clinical trials relate to the
surgical procedure itself, the outcome of the trial of interest, surgical
philosophy, and the ethical implications for a surgeon of a randomized
clinical trial. A recently proposed variation of the classic randomized
clinical-trial model, the randomized-surgeon design, appears to solve some
of these problems.