A Hip Arthroscopy Paper: Circulus in Probando

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I recently read an orthopedic Hip Arthroscopy paper that made me LOL. Why? Orthopedic surgeons just write the darndest things. This one is guilty of circular reasoning. Let me explain.

Circulus in Probando

There’s a logical fallacy that in English is called circular reasoning, but in Latin, it’s “circulus in probando” (circle in proving). Basically, the argument begins with the conclusion that it wants to end with. Or, if A is true, then B is true and if B is true than A is true, without ever really looking at whether A or B in isolation is actually true. You’ll see what I mean when we look at the paper highlighted below.

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Does Hip Arthroscopy Work?

One of the more common orthopedic surgical procedures that has exploded in use over this past decade is Hip Arthroscopy. These procedures involve sewing back together a torn labrum, reshaping the socket or hip bone, removing damaged cartilage, or poking holes in the bone to try and get fibro-cartilage to develop. The most common clinical indication is Hip Impingement, otherwise known as FAI. Does the procedure work? We really don’t have research that compares the procedure to a sham procedure or placebo so we don’t really know.

A good review of this topic on the lack of evidence that common orthopedic surgeries are effective can be found in this recent blog post. The conclusion was that 9 of the 10 most common surgeries don’t have gold-standard evidence of efficacy.

A Nutty Hip Arthroscopy Study

Through the years I’ve highlighted all sorts of studies that claim to conclude one thing, but lack the methodology to prove that thing. Or, like these this study, produce data that says X and then conclude Y. Surprisingly, this study was published in a respected medical journal.

This new study represents some early results from a randomized controlled trial on Hip Arthroscopy performed to treat impingement (FAI) (1). The researchers had three groups:

  • Lavage (flushing the joint out with water, which would be a placebo or close to it)
  • Two groups who got Hip Arthroscopy where the shape of the joint was altered (osteochrondroplasty)

Outcomes were collected at 12 and 24 months and here’s what the researcher found when comparing the placebo to the actual hip surgery:

“All groups had improvements across all questionnaire outcomes from baseline to 12 months, with no significant differences.”

Hence, at the end of the day, the study showed that this Hip Arthroscopy procedure was no better than the placebo procedure, right? Well, that’s not what the study concluded, which was:

“Hip arthroscopic osteochondroplasty and lavage led to improvement in hip pain, function, and health-related quality of life at 12 months across both randomized controlled trial (RCT) and cohort patients. The pragmatic cohort receiving osteochondroplasty had (1) significantly fewer complications than RCT patients, (2) significantly less reoperations than RCT patients randomized to arthroscopic lavage, and (3) fewer, although nonsignificant, reoperations than RCT osteochondroplasty patients.”

Huh? That’s a bunch of medical jargon, but they conclude that since these surgeons decided that more placebo patients needed the actual Hip Arthroscopy (which was no better than the placebo), then the Hip Arthroscopy was better than the placebo. If that logic makes no sense, you’re right! This is why they seem to have inserted the word “pragmatic” in the title. Inserting the word “illogical” or “silly” would have been more accurate.

As you can see, this is evidence of circular reasoning. We don’t know that Hip Arthroscopy works and in fact, in the study, it was no better than placebo. However, since more people who got the placebo eventually decided they wanted the hip surgery, that means that arthroscopy is more effective?

The upshot? We need good data showing that Hip Arthroscopy is better than a sham or placebo surgery (like lavage). Despite the linguistic origami used by the authors, this study isn’t it. Regrettably, this is becoming more common in the orthopedic surgery literature.



(1) Almasri M, Simunovic N, Heels-Ansdell D, Ayenil OR; FIRST Investigators. Osteochondroplasty Benefits the Pragmatic Patient With Femoroacetabular Impingement: Analysis From the Embedded Prospective Cohort of the Femoroacetabular Impingement RandomiSed Controlled Trial (FIRST). Arthroscopy. 2021 Jul 9:S0749-8063(21)00650-2. doi: 10.1016/j.arthro.2021.06.026. Epub ahead of print. PMID: 34252556.

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Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications. View Profile

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