Here is a study that illustrates everything that is wrong with the current status of evidence-based surgical practice.
Many of the standard procedures we perform in general surgery are based on observational studies, expert opinion or my favorite “That’s the way I was trained,” and not randomized controlled trials. Although some such research has been done, subjecting patients to sham operations raises ethical issues and would expose patients to anesthesia unnecessarily.
But some topics could be studied prospectively. A recent paper  [Variation in the use of intraoperative cholangiography during cholecystectomy. Sheffield KM et al. J Am Coll Surg. 2012;214:668-79] highlights the problem of insufficient evidence in some areas of surgery.