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Examining Randomized Controlled Trials for Surgery

We have all heard of randomized controlled trials (RCTs) being used for pharmaceutical products, where one group receives the actual drug and the other receives a placebo. The results of the trial indicate whether the true medicine has a positive effect that is greater than the one potentially caused by the placebo. But what are the limits of RCTs? Can we use them for something like surgery?

As it turns out, the answer is yes.

One essential component of an RCT is that patients don’t know whether they are receiving the real drug or the placebo. Even better is when the physician examining their condition doesn’t know whether the patient received the real treatment or the placebo. This way, we can distinguish the placebo effect from the treatment effect, and the evaluators are not biased in the way they analyze patients from the control and treatment groups.

It is possible to give people sham surgeries to understand whether the surgery truly has any benefit. Although controversial, RCTs for surgeries are not unheard of. One example of a RCT for surgery is found in a 2002 article published in the New England Journal of Medicine.

The surgery in question was arthroscopy, a surgery of the knee in which a small incision is made to insert a camera that can then be used to guide small tools to do the necessary work. As the authors of the study explain in the abstract, “Many patients report symptomatic relief after undergoing arthroscopy of the knee for osteoarthritis, but it is unclear how the procedure achieves this result.”

Could it be that the benefit from this study is entirely due to the placebo effect? 180 total patients with osteoarthritis of the knee agreed to be randomized into control and treatment groups for the surgery.

The control group received a placebo surgery, where the surgeon made incisions in the knee but did not carry out the full procedure. Although the patients were given tranquilizer and were breathing oxygen-enriched air, the surgeon pretended to be handling the tools for the real procedure in case the patients were still conscious of what was going on. There were two different treatment groups, each with a different type of surgical intervention.

Although surgeons obviously knew whether they were assigned to the treatment or control groups, the physicians assessing the patients’ conditions over the course of 2 years were blind to this fact. Over the course of 24 months, patients would give their ratings of the pain and function of the knee that had been worked on, and assessors also measured how well these individuals could climb up stairs.

The results were that there was no statistical difference between the control and treatment groups in pain or function over the two-year study period. At no point did the treatment groups score better in pain or function metrics than the placebo groups.

One major limitation of the study is that the individuals who agreed to participate in the study are not representative of the population that goes in for arthroscopic knee surgery.

As the authors explain in their study, “A selection bias might have been introduced by the fact that 44 percent of the eligible patients declined to participate in the study. We believe this high rate of refusal to participate resulted from the fact that all patients knew they had a one-in-three chance of undergoing a placebo procedure. Patients who agreed to participate might have been so sure that an arthroscopic procedure would help that they were willing to take a one-in-three chance of undergoing the placebo procedure. Such patients might have had higher expectations of benefit or been more susceptible to a placebo effect than those who chose not to participate.”

In addition, the study was performed in a Veterans Affairs hospital, so almost all of the patients were men. That makes the findings more difficult to generalize. Finally, having only 60 people in each group makes it more difficult to find statistically significant findings.

A more recent sham surgery on certain types of shoulder injuries had a more representative population, but also suffered from the same issue with a small number of individuals in each of the groups, since only 118 people were randomized into 3 different groups.

For all groups, incisions were made in their shoulders, and their arms were put in slings after the operation. All of the groups made significant improvements in pain measurements and function after the surgery, regardless of whether they had the sham surgery. In fact, the improvements for all three groups happened at almost identical rates across a 2-year period.

The authors acknowledge the limitations of their study, but also suggest that there is an overtreatment of patients who have the type of lesion studied in the paper. They suggest that nonsurgical interventions like physical therapy (which the participants in the study underwent after the surgery or sham surgery) as a way to solve the issue without a smaller risk of complications.

There are certainly ethical questions to RCTs with surgeries, not to mention difficulties in finding statistically significant results with few willing participants. It is hard to get a large representative sample of people to sign a document stating that they might receive a placebo surgery.

There are also not a lot of incentives to run RCTs with surgery, and not only because they are difficult to conduct. Physicians do not want to hear that the technique they may have spent decades perfecting doesn’t actually do anything. In addition, in the US, insurance companies may make a lot of money from certain procedures, so they wouldn’t want to see fewer of them.

Nevertheless, it is still important if we know that a patient’s improvement after an invasive procedure is due to the procedure itself or simply the placebo effect. RCTs are an essential component in advancing our knowledge of some surgical techniques.


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