A number of studies done under
Institutional Review Board-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. A review of studies with sham surgery found 53 such studies: in 39 there was improvement with the sham operation and in 27 the sham procedure was as good as the real operation. Sham-controlled interventions have therefore 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.
Central nervous system disease 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 to be ineffective and possibly harmful. Subsequently, over 90% of surveyed investigators believed that future neurosurgical interventions (e.g.
gene transfer therapies) should be evaluated by sham-controlled studies as these are superior to open-control designs, and have found it unethical to conduct an open-control study because the design is not strong enough to protect against the placebo effect and bias. They found that patients in the treatment group 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. In a 2016 study it was found that arthroscopic partial meniscectomy does not offer any benefit over sham surgery in relieving symptoms of knee locking or catching in patients with degenerative meniscal tears. A randomised controlled trial was carried out to investigate the effectiveness of shoulder surgery to remove an acromial spur (bony protuberance on x-ray) in patients with shoulder pain. This found that improvement after sham surgery was as great as with real surgery. A systematic review has identified a number of studies comparing orthopedic surgery to sham surgery. This demonstrates that it is possible to undertake such studies and that the findings are important. ==Animal research==