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In clinical trials of surgical interventions, sham surgery is an important scientific control. This is because it isolates the specific effects of the treatment as opposed to the incidental effects caused by anesthesia, the incisional trauma, pre- and postoperative care, and the patient's perception of having had a regular operation. Thus sham surgery serves an analogous purpose to placebo drugs, neutralizing biases such as the placebo effect.
The placebo-controlled trial is the gold standard of medical research. Therefore, when testing results of a surgical procedure, sham surgery serves as the intervention in the control population. However, the use of sham surgery in human research is controversial as it places ethical and research standards into conflict. While sham surgery has the potential to harm the subject, research designs without sham surgery are scientifically less rigorous. Proponents argue that surgical interventions need to be tested as critically as medical interventions. One partial solution is that when a clinical trial is over, those people who received sham surgery may be offered a second surgery including the actual treatment. Because of the ethical concerns, sham-controlled studies are rarely performed in humans.
A number of studies done under IRB-approved settings have delivered important and surprising results. With the progress in minimally invasive surgery, sham procedures can be more easily performed as the sham incision can be kept small similarly to the incision in the studied procedure.
In a number of situations, sham-controlled interventions have identified interventions that are useless but had been believed by the medical community to be helpful based on studies without the use of sham surgery. Thus in 1939 Fieschi introduced internal mammary ligation as a procedure to improve blood flow to the heart. Not until a controlled study was done two decades later could it be demonstrated that the procedure was only as effective as the sham surgery. In neurosurgery, cell-transplant surgical interventions were offered in many centers in the world for patients with Parkinson disease until sham-controlled experiments involving the drilling of burr holes into the skull demonstrated such interventions ineffective and possibly harmful. Subsequently over 90% of surveyed investigators believed that future neurosurgical interventions (i.e. gene transfer therapies) should be evaluated by sham-controlled studies as these are superior to open-control designs, and half found it unethical to conduct an open-control study because the design is not strong enough to protect against the placebo effect and bias. Kim et al. point out that sham procedures can differ significantly in invasiveness, for instance in neurosurgical experiments the investigator may drill a burr hole to the dura mater only or enter the brain.
In a classic experiment in orthopedic surgery, Moseley and coworkers studied the effect of arthroscopic surgery for osteoarthritis of the knee establishing two treatment groups and a sham-operated control group. They found that patients in the treatment arms did no better than those in the control group. The fact that all three groups improved equally points to the placebo effect in surgical interventions.
While some ethicists reject sham-surgery in controlled trials, others maintain that such trials are ethically acceptable but should conform to certain restrictions. Such restrictions include that the research question is important and cannot be answered by other forms of research, further the risk of the sham procedure should be kept as minimal as possible and the informed consent needs to be appropriate with subjects being aware of the risks and that they may receive placebo surgery.
Sham surgery has been widely used in surgical animal models. Historically, studies in animals also allowed the removal or alteration of an organ; using sham-operated animals as control, deductions could be made about the function of the organ. Sham interventions can also be performed as controls when new surgical procedures are developed.