Related Experiment Video
Updated: Jun 12, 2025
In Vitro Application of a Wireless Sensor in Flexion-Extension Gap Balance of Unicompartmental Knee Arthroplasty
Published on: May 5, 2023
Kinematic vs. mechanical alignment in total knee arthroplasty: A statistical analysis of randomized control trials
Adriano Cuadros1, Michaela Corvi2, Avanish Yendluri1
1Department of Orthopedic Surgery, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Pl, New York, NY, USA.
Purpose:
Randomized controlled trials (RCTs) that assess kinematic alignment (KA) versus mechanical alignment (MA) in total knee arthroplasty (TKA) report p-values that influence surgical decision-making. This study utilizes fragility index (FI) and fragility quotient (FQ) metrics to assess the statistical stability of outcomes reported in RCTs comparing KA and MA approaches in TKA.
Methods:
Pubmed, Embase, and MEDLINE were queried for RCTs evaluating KA vs MA approaches in TKA. The FI and reverse fragility index (rFI) were calculated for dichotomous outcomes and were defined as the number of event reversals needed to alter the statistical significance for significant and non-significant outcomes, respectively. The continuous fragility index (cFI) was used to evaluate statistically significant continuous variables and was calculated using a novel online tool. The FQ was calculated by dividing the FI, rFI, or cFI by sample size.
Results:
The median FI across 58 included outcomes was 7.0 (FQ 0.109). Overall, dichotomous variables were more fragile than continuous variables. The 12 dichotomous outcomes were all statistically non-significant, with a median rFI of 4.5 (FQ 0.040). The 46 continuous outcomes were all statistically significant, with a median cFI of 9.1 (FQ 0.113). In 21 of 58 outcomes, the number of patients lost to follow up was greater than the FI for the respective outcome. When analyzing by outcome category, clinical improvement and complications were more fragile, with median FIs of 6.7 and 5.0.
Conclusion:
Continuous outcomes were more robust than the relatively fragile dichotomous outcomes. The continuous outcomes in KA versus MA RCTs were also more robust compared to other current studies reporting cFI values. cFI is a novel, valuable tool that allows for assessment of fragility for continuous outcomes, and reporting alongside FI, rFI, and FQ with p-values is recommended to assess the reliability of RCTs.
