Sham surgery is essentially a placebo surgery: the patient is anesthetized, the surgeon makes some incisions, and then the incisions are sewed up and the patient is restored to consciousness. Because all the evidence suggests that the patient really did have a surgery, he or she will believe that the surgery took place. Sham surgery is used in some research trials to test the efficacy of surgical techniques, although the practice is not without controversy.

In several clinical trials, including a study on Alzheimer's patients and a study on patients with knee problems, sham surgery actually worked better than the real surgery, in terms of patient response. Over a period of extensive followup, patients who had undergone sham surgery indicated that they had experienced positive results after the surgery, with significant improvement in body function and quality of life. This raised interesting questions about the role of patient expectations in surgical treatment, and about how sham surgery should be used.

In most clinical trials for things like drugs, the subjects are divided into several groups and given doses of the medication being taken or a totally inert placebo. Typically such studies are “double blind,” meaning that the people administering the medication don't know whether the patients are getting the real thing, or a placebo. This measure is designed to reduce the influence of expectations on the outcome as the trial, as expectations clearly have a strong influence on the efficacy of a treatment. When examining the results of a study to see whether or not a drug works, therefore, people look at the response of people in the placebo group as compared to those taking the actual medication.

Sham surgery is offered along similar lines. Patients are informed when they enter the study that they may receive an actual surgery, or a placebo surgery, ensuring that the study's architects have what is known as “informed consent,” and then all of the patients are anesthetized to provide the illusion of surgical conditions. When they wake up from the “surgery,” sham surgery patients are given the same care as regular surgical patients, typically from nurses and other support staff who don't know whether the patients received the surgery or a placebo. If the surgical treatment being tested is really effective, patients who received the real surgery will substantially improve, while placebo patients should see no change, despite their belief that they received the surgery.

This practice encounters some thorny ethical issues. Some ethicists are opposed to sham surgery, arguing that a sham surgery, unlike a drug placebo, is not actually inert. Surgery carries a number of potential risks, so subjecting people to anesthesia and its associated risks along with the risks of infection seems questionable. However, the success of sham surgeries in the testing of surgical techniques has suggested that perhaps placebo surgeries do have a place in carefully monitored studies.