In this situation, there are three competing events: revision surgery for recurrent dislocations, revision surgery for any other reason and death of a patient.
The goal is to calculate the required number of patients that will yield a sufficient number of outcome events (revision surgeries) in order to have adequate statistical power for a given size of treatment effect.
The difference in risk was calculated using the number of events (revisions) and persons at risk 10 years after the index operation.
T. Pico, J.X. Mitrovica, A.C. Mix, "Sea-level fingerprinting of the Bering Strait flooding history detects the source of the Younger Dryas climate event", (in revision, Nature Geoscience).
From a methodological point of view however, a prospective design for investigation of the relatively rare event of revision needed after RTSA would demand high resources and most probably a multicenter design.
Immediately at final follow-up (12.8 years), the calculated survival rate dropped to 44% (CI: 1 86) because 1 event (cup revision) occurred at the final follow-up when only 1 other hip was still under follow-up.
Changes and events requiring revision of articles are more readily apparent in the scientific, technological, biographical, and historical areas, with the result that articles in such fields are revised much more frequently than articles in such fields as the humanities, where important changes do occur, though more subtly.
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Patients who wait more than 3 months for idiopathic scoliosis surgery have higher probability of adverse events and revision surgery rates.
The hazard rate is the instantaneous rate of an event, for example revision, amongst those still at risk of experiencing revision.
