Epistemological angle: This is the base rate for surgery itself, and it belongs in a surgeon's head before any individual outcome study is read. When roughly half of the procedures that have been tested this way fail to beat placebo, an uncontrolled case series reporting good results carries almost no evidential weight — it is exactly what you would expect to see whether or not the operation does anything. The paper also answers the practical objection to sham trials by demonstration: they were done, they were feasible, and the risk was low.

Epistemological angle: Before this trial, the evidence for knee arthroscopy in osteoarthritis was consistent, abundant, and entirely uncontrolled. Patients did improve. The inference from "they improve after surgery" to "the surgery improved them" is the one this design breaks, and it turns out to have been carrying the whole weight. Regression to the mean, natural history, and the substantial expectation effects of an operation account for the observed benefit without requiring the mechanism anyone believed in.

Epistemological angle: The tear was the reference class. It was the finding that assigned the patient to the operable group, that justified the arthroscope, and that explained the pain afterwards. FIDELITY shows the assignment does not license the operation: removing the thing did not remove the symptom. That is a weaker claim than showing the tear to be causally inert, and the difference is worth holding onto — a process may be irreversible by the time it is found, or the surgery's own costs may offset what it gains. But it is enough for the clinical question, because the assignment's entire purpose was to justify removal. Read alongside entry 12, which establishes that most people of this age have such a tear and most of them have no pain, the two papers form a complete argument — here is the base rate that should have warned us, and here is the trial that eventually did.

Epistemological angle: Two lessons in sequence, and the second undoes the comfortable reading of the first. A single negative trial invites the reply that this trial was flawed; two independent trials in different countries with different designs and the same null move the question from the trials onto the intervention, and the epistemic gain comes from the independence rather than from the combined sample size. INVEST adds that blinding and crossover-resistance are separate problems, with 51% of its sham arm crossing to real vertebroplasty by three months against 13% the other way. Then VAPOUR states the reference class problem as a trial. It did not refute the 2009 results; it redrew the boundary of who was being asked about. "Does vertebroplasty work" was never a well-formed question — only "in fractures of what age, what severity, filled to what extent" is answerable, and every null result carries an implicit population that the headline discards. Whether VAPOUR's chosen class is the right one remains contested, largely on the adequacy of its blinding.

Epistemological angle: The independence argument of entry 4, repeated in a second procedure, and with a sharper design. CSAW's three-arm structure separates two questions that a two-arm sham trial has to answer together: what does the specific surgical act contribute, and what does the whole surgical episode contribute. The answer is that the act contributes nothing detectable and the episode contributes a little. That decomposition is what makes these trials the natural terminus of the arc begun at entry 8: Neer's mechanism was proposed in 1972, the diagnosis built on it, the operation built on the diagnosis, and forty-six years later the mechanism-specific step turned out to be the part that was doing nothing.

Epistemological angle: This complicates the lazy reading of every trial above. "It was just the placebo effect" sounds like an explanation, but if placebo is generally weak, then a sham arm matching a real operation is a far harsher verdict than that phrase implies — it means the operation was doing very little, not that placebo was doing a great deal. And the finding that procedural placebos outperform pill placebos is what makes surgical sham controls necessary rather than borrowable: surgery could not import its intuitions from drug trials, because the placebo in surgery is a different and larger thing.

Epistemological angle: The cleanest empirical demonstration of the adopt-versus-abandon asymmetry available in orthopaedics. Kyphoplasty was never held to the standard eventually applied to vertebroplasty; it entered practice on plausibility and stayed there. When disconfirming evidence arrived for the tested procedure, demand migrated to the untested cousin. No individual made an irrational decision, and the aggregate result was that a sham-controlled refutation produced a change in billing codes rather than a change in whether patients had cement injected.