Fragility of randomized controlled trials comparing cemented and cementless components in total knee arthroplasty: A systematic review

Background: The use of cemented versus cementless components in total knee arthroplasty (TKA) remains a subject of ongoing debate, with a recent rise in cementless TKA. In this study, we assessed the robustness of outcomes reported in randomized controlled trials (RCTs) comparing cemented and cementless components in TKA. Methods: PubMed, Embase, and Medline were queried from January 1, 2010-February 28, 2024 for RCTs with intervention arms stratified for cemented and cementless TKA components. The fragility index (FI) and reverse fragility index (rFI) were defined as the number of outcome event reversals needed to alter outcome significance. The fragility quotient (FQ) was determined by dividing the FI or rFI by the study sample size. Results: From 176 screened RCTs, 13 studies met inclusion criteria, yielding 48 total outcomes. There were 13 statistically significant outcomes which had a median FI of 4. Thus, the significance of these outcomes may be lost by 4 patient outcome event reversals. Furthermore, an outcome event reversal in 4.1% of patients (median FQ 0.041) may be sufficient to reverse statistically significant outcomes. The median rFI across the 35 non-significant outcomes was found to be 5. In a subanalysis by outcome type, outcomes relating to component migration were found to be most fragile with a median FI of just 2. The median FI for radiolucency and complication outcomes were both equal to 5, while the median FI's for function and satisfaction were both 8. In 46% of outcomes, the number of patients lost to follow-up exceeded the outcome FI/rFI. Conclusion: RCTs comparing cemented versus cementless TKA have considerable clinical implications in surgical decision-making, yet the outcomes in these studies are statistically fragile. Standardized reporting of FI, rFI, and FQ metrics may facilitate a more comprehensive assessment of the stability of study outcomes in TKA RCTs.