How robust are clinical trials in primary and secondary ankle sprain prevention?

C M Bleakley, Jente Wagemans, Alexander Schurz, James Smoliga

Research output: Contribution to journalArticlepeer-review


Determine the statistical stability of RCTs examining primary and secondary prevention of ankle sprains.
Databases were searched to August 2023. We included parallel design RCTs, using conservative interventions for preventing ankle sprain, reporting dichotomous injury event outcomes. Statistical stability was quantified using Fragility Index (FI) and Fragility Quotient (FQ). Subgroup analyses were undertaken to test if FI varied based on by study objective, original approach to analysis (frequency vs time to event), follow-up duration, and pre-registration.
3559 studies were screened with 45 RCTs included. The median number of events required to change the statistical significance (FI) was 4 (IQR 1-6). FI was similar regardless of study objective, original analysis, follow-up duration, and pre-registration status. Median (IQR) FQ was 0.015 (0.005-0.046), therefore reversing events <2 patients/100 would alter significance. In 80% of studies the number of patients lost to follow-up was greater than the FI.
RCTs informing primary and secondary prevention of ankle sprain are fragile. Only a small percentage of outcome event reversals would reverse study significance, and this is often exceeded by the number of drop outs. Robust reporting of dichotomous outcomes requires the use P values and key metrics such as FI or FQ.
Original languageEnglish
Pages (from-to)85-90
Number of pages6
JournalPhysical Therapy in Sport
Early online date26 Aug 2023
Publication statusPublished (in print/issue) - 1 Nov 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier Ltd


  • P values
  • Statistical Fragility
  • Injury Prevention
  • Ankle sprain
  • Statistical fragility
  • Injury prevention


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