A study that finds nothing is often the most useful kind. This one found nothing, and then described what it found in a way worth separating from the data.
What was compared
Adults with type 2 diabetes who had a primary knee replacement between mid-2022 and the end of 2024, and who had an active prescription for semaglutide or tirzepatide within the 90 days before surgery. [1] They were matched one to one on age, sex, race, BMI, glycated hemoglobin, comorbidity burden and concurrent diabetes medication, leaving 415 pairs. Outcomes were tracked to 90 and 180 days.
Nothing reached significance. Medical complications at 90 days came in at OR 1.122, 95% CI 0.736 to 1.710. Surgical complications at 180 days at OR 1.632, 95% CI 0.845 to 3.152. Individual events — heart attack, stroke, pneumonia, sepsis, clots, kidney injury, wound problems, joint infection, death, revision — were all similar, every p above 0.05.
The sentence that goes further than the data
The authors conclude that the two drugs demonstrated similar short-term safety and utilization profiles, and that the findings support continued perioperative use of either agent.
The first half is a reasonable summary of a null result if you read “similar” loosely. The second half is a recommendation, and a failure to detect a difference among 830 patients does not establish that no difference exists. To conclude equivalence you need a study designed to rule out a difference of a stated size, and this was not one — it is the same distinction between what a design was built to answer and what gets claimed from it.
Not the opposite claim either
None of this suggests either drug is risky around surgery. The point estimates cluster near no difference, nothing looked alarming, and the study is perfectly good evidence that no large difference was detected.
The honest position is narrower than either headline: on this evidence nobody can tell the two apart for knee replacement, and the reason is that nobody has looked at enough patients. Whether these drugs should be paused before surgery at all is a separate question with its own page here, and it is the question a patient is more likely to face.
Why this pattern matters beyond knees
Because “no significant difference” is the most frequently over-read phrase in medical writing. It gets reported as reassurance, quoted as equivalence, and eventually cited as evidence that two things are the same.
The test takes a moment: look at the interval rather than the p-value, and ask what the upper bound would mean if it were true. If it would matter, the study did not settle anything. Almost nothing a seller publishes includes an interval at all, which the census of what goes unsaid measures from the other end.