One of the findings of this comprehensive review was the lack of high-quality evidence for most of the procedures, specifically a lack of RCTs. The authors point out that this does not indicate a lack of effectiveness, but rather that their common usage is based on expert opinion, observational trials, etc. While RCTs may offer supportive evidence, this has not always been the case; for example, when subjected to RCT, a commonly performed arthroscopic surgery for osteoarthritis of the knee was shown to provide no additional benefit, and now is actively recommended against for nearly all patients with degenerative knee pain.
This umbrella review did find positive evidence supporting total knee replacement and strong evidence for carpal tunnel decompression compared to non-operative care. However, existing RCTs found similar outcomes to non-operative care for many of these common procedures, including arthroscopic anterior cruciate ligament reconstruction, arthroscopic partial meniscectomy, arthroscopic repair for acute rotator cuff tears, arthroscopic subacromial decompression, lumbar spinal decompression for spinal canal stenosis, and spinal fusion for degenerative disc disease. No RCTs exist comparing total hip replacement or meniscal repair for acute tears of the knee to non-operative care. The authors suggest that while observational evidence may be so overwhelming as to make RCTs redundant in some cases (hip replacement may be an example), most of these procedures urgently need better RCT data to clearly identify benefit, as well as subsets of patients that may benefit even if the larger patient population would not.